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  • kinetics  (63)
  • phosphorus  (43)
  • Springer  (106)
  • Institute of Physics
  • 1995-1999
  • 1990-1994  (106)
  • 1940-1944
  • 1992  (106)
Collection
Keywords
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Years
  • 1995-1999
  • 1990-1994  (106)
  • 1940-1944
Year
  • 1
    Electronic Resource
    Electronic Resource
    Effect of ionic interactions on the rates of reduction of Cu(II) with H2O2 in aqueous solutions (1992)
    Springer
    Journal of solution chemistry 21 (1992), S. 1271-1287 
    Details
    ISSN: 1572-8927
    Keywords: Cu(II) ; kinetics ; reduction ; temperature dependence ; H2O2, NaCl, NaBr, NaClO4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The rates of reduction of Cu(II) with H2O2 have been measured in NaCl and NaBr solutions and mixtures with NaClO4 as a function of pH (6 to 9), temperature (5 to 45°C) and ionic composition (0.1 to 6M). The effect of pH on the rates was found to be independent of temperature and ionic composition. The rates increased as a function of [H+] raised to the power of 1.3 to 1.6. Speciation calculations indicate that this pH dependence can be attributed to Cu(OH)2 being the reactive species. The rate constants in NaCl and NaBr and mixtures with NaClO4 were independent of ionic strength, but proportional to the halide concentration raised to the power of 2.0 (0.2 to 2.6M). These results can be attributed to Cu(OH)2Cl 2 2− being the reactive species to reduction with H2O2. The Cu(I) halide complexes formed from the reduction are not easily oxidized with O2 or H2O2. The faster rates in Br− solutions, which form stronger complexes with Cu+, support this contention. Measurements made in NaCl with added NaHCO3, NaB(OH)4 EDTA, NTA and glycine were also made. These measurements indicate that the CuL complexes (L=B(OH) 4 − , CO 3 2− , EDTA, NTA, and glycine) are not very reactive to reduction with H2O2. The addition of Mg2+ or Ca2+ caused the rates to increase due to the formation of MgL or CaL complexes and the resultant release of reactive Cu2+.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00667222
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  • 2
    Electronic Resource
    Electronic Resource
    Measurement of total dissolved phosphorus in small volumes of iron rich interstitial water (1992)
    Springer
    Aquatic sciences 54 (1992), S. 1-9 
    Details
    ISSN: 1420-9055
    Keywords: Sediment ; interstitial water ; phosphorus ; iron ; persulfate digestion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It is shown that sorption of orthophosphate to iron compounds, formed during persulfate digestion, can cause a significant underestimation of total dissolved phosphorus in interstitial waters rich in iron and poor in phosphorus. Labelling the samples with carrier free32PO4 before digestion allows to correct for these losses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877261
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  • 3
    Electronic Resource
    Electronic Resource
    The determination of phosphonate base scale inhibitors in brines by plasma spectrometry (1992)
    Springer
    Microchimica acta 109 (1992), S. 201-209 
    Details
    ISSN: 1436-5073
    Keywords: phosphonate base scale inhibitor ; brine ; direct current plasma ; inductively coupled plasma atomic emission spectrometry ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The determination of phosphonate base scale inhibitors in brines by direct current plasma (DCP) and inductively coupled plasma atomic emission spectrometry (ICP-AES) is described. The first method is based on a direct nebulization of the brine samples and plasma using the phosphorus line at 213.618 nm. The second method involves extraction of phosphorus as phospho-antimonyl molybdate complex into methylisobutyl ketone (MIBK) phase and analysis of the extract for molybdenum using the Mo 313.260 nm line. Comparison between the proposed methods and an established recommended method [1] shows excellent agreement between the results in addition to the sensitivity and ease of automation provided by AES.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01242475
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  • 4
    Electronic Resource
    Electronic Resource
    Increased sensitivity of an enzyme immunoassay (ELISA) for the determination of triazine herbicides by variation of tracer incubation time (1992)
    Springer
    Microchimica acta 108 (1992), S. 29-40 
    Details
    ISSN: 1436-5073
    Keywords: atrazine ; terbuthylazine ; sequential binding ; kinetics ; cross-reactivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Immunoassays for triazine herbicides were tested for their reaction to the variation of the tracer incubation time. By application of a sequential technique the measuring range of atrazine could be expanded to five decades and the total duration of the test could be reduced to about 30 min. In an optimized version a lower detection limit of 9 pmol/l (2 ng/l) was achieved. The detection limit of a sensitive immunoassay for terbuthylazine is also below the concentration limit demanded of the German drinking water regulation (100 ng/l) and reaches 130 pmol/l (30 ng/l). Short tracer incubation times did not lead to increased cross-reactivities in contrast to theoretical models [1, 2]. Different mechanisms, which could cause a shift of the center point of the calibration curve, are discussed, including kinetic considerations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01240369
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  • 5
    Electronic Resource
    Electronic Resource
    The interpretation of Olsen extractable P values in relation to recommendations for the fertilizer requirements of crops (1992)
    Springer
    Nutrient cycling in agroecosystems 32 (1992), S. 223-227 
    Details
    ISSN: 1573-0867
    Keywords: Soil testing ; phosphorus ; relative yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A greenhouse experiment, with Okra (Abelmoschus esculentus L.) as the test crop, was conducted on twenty-one soils ranging in Olsen's extractable phosphorus from 1.8 to 15.5µg Pg−1 soil. The experiment was conducted at Punjab Agricultural University, Ludhiana, India. The soils were nonsaline with pH ranging from 7.7 to 8.6. A critical level of 2.55µg Pg−1 soil was predicted by Cate and Nelson's (1971) statistical procedure. Because of a wide range in relative yields, this value did not accurately predict response to applied P. An approach to compute minimum response to applied fertilizer, which is likely to be obtained at a particular Olsen P level, has been presented. It involves calculation of lower 60 percent confidence limits for relative yield and fitting loge-linear regression to the transformed data. The regression was tested on a published data set and was found to hold well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01048784
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  • 6
    Electronic Resource
    Electronic Resource
    Two post thinning fertilizer trials inPinus radiata in New South Wales, Australia (1992)
    Springer
    Nutrient cycling in agroecosystems 32 (1992), S. 259-267 
    Details
    ISSN: 1573-0867
    Keywords: Nitrogen ; phosphorus ; timber increment ; fertilization ; Pinus radiata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two trials inPinus radiata growing on different sites in N.S.W. allowed consideration of fertilizer applications after 2nd or 3rd thinning. The trials included factorial applications of N and P at a single thinning intensity plus a further treatment which allowed assessment of different thinning intensities. The most significant growth responses were obtained by application of N and P in combination. The largest response (additional productivity compared with the unfertilized control) occurred 4 years after application and after 7 years there was no additional absolute response for either of the two sites. The largest fertilizer response was 70 m3 ha−1 over 7 years on one site and 36 m3 ha−1 on the other, indicating differences in absolute responses between sites. It was concluded that in planning treatments the most responsive sites near the end of the rotation should be selected to maximise economic returns. Foliage analyses indicated differences between sites at the commencement of the study. It was concluded that either a single year of foliage analyses at study commencement is of value, or sampling every year of the study should be used to analyse responses, but a single year of analysis during or at the end of the study would not be of value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01050363
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  • 7
    Electronic Resource
    Electronic Resource
    Nutrient-chlorophyll trajectories across trophic gradients (1992)
    Springer
    Aquatic sciences 54 (1992), S. 58-76 
    Details
    ISSN: 1420-9055
    Keywords: Eutrophication ; lake management ; phosphorus ; nitrogen ; chlorophyll-a ; slope estimator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We estimate the response of chl-a (mg · m−3) to changes in concentrations of total phosphorus (TP) by calculating the slopeS = Δchl-a/ΔTP in chl-a =f(TP) graphs. Results show that in years where algae are P-limited oligotrophic lakes respond less (median slope 0.21) to changes in nutrient concentrations than eutrophic lakes, (median slope 0.31) and these again less than hypereutrophic lakes, (median slope 1.02). We find no saturation value for the slope within the TP range considered (6–480 mg · m−3). Chl-a in eutrophic lakes responds more frequently to non-nutrient factors than oligotrophic and hypereutrophic lakes. Results obtained by replacing TP with a new nutrient parameter, TP′ = 0.056 · TP · IN0.226, in which inorganic nitrogen, IN, is factored in, suggest that nitrogen has an influence on chl-a in oligotrophic lakes. Blue-green algae respond less to changes in TP than other algal species, e.g., diatoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877264
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  • 8
    Electronic Resource
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    Possibilities and limitations of lake restoration: Conclusions for Lake Lugano (1992)
    Springer
    Aquatic sciences 54 (1992), S. 381-390 
    Details
    ISSN: 1420-9055
    Keywords: Eutrophication ; phosphorus ; lake restoration ; internal restoration measures for lakes ; Swiss lakes ; Lake Lugano (Lago di Lugano)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In most lakes eutrophication is linked to an excessive input of phosphorus. Lake restoration by reduction of P-input (external measure) has led to a considerable drop of the P-concentration in all major Swiss lakes as well as in many other lakes. Internal restoration measures such as artificial mixing, drainage of hypolimnetic water, flushing, aeration, biomanipulation and others serve to improve and accelerate the response of a lake to external measures. For the case of Lago di Lugano, a simple two-box model is employed to demonstrate that a reduction of the P-input to about 25% of the present values is necessary to reach the “P-criterion” (P-concentration below 30 µg/l). Internal measures could possibly accelerate the extremely slow response of the northern basin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00878149
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  • 9
    Electronic Resource
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    Absorption of intramuscular phenobarbitone in children with severe falciparum malaria (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 107-110 
    Details
    ISSN: 1432-1041
    Keywords: Phenobarbitone ; Cerebral malaria ; P.falciparum ; kinetics ; drug absorption ; children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absorption of intramuscular phenobarbitone 7 mg·kg−1 was studied in 11 Karen children aged between 1.7 and 11 y with severe falciparum malaria. Eight of the children were comatose. Clinical findings were compared with those in 9 further children with severe malaria of similar age range (four of whom were unconscious), who received an identical placebo. One child, who had received placebo, had repeated convulsions and died 1 h after admission to hospital. The remainder made an uncomplicated recovery. There were no convulsions subsequent to treatment, although the study was too small to assess anticonvulsant efficacy. There was no observable toxicity, but phenobarbitone recipients had a significant tendency to deepen in their level of coma or to become sleepy within the 4 h after drug administration. Phenobarbitone was rapidly absorbed, reaching a mean (range) peak concentration of 34.2 [29.3–42.6] μmol·l−1 in a median (range) of 4 (2.5–12) h. These values are comparable to those previously reported in healthy children and in children with febrile convulsions. Intramuscular phenobarbitone is well absorbed in children with severe malaria; the optimum prophylactic anticonvulsant dose remains to be determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00314929
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  • 10
    Electronic Resource
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    Kinetics of atrial natriuretic peptide in young and elderly subjects (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 449-452 
    Details
    ISSN: 1432-1041
    Keywords: Atrial natriuretic peptide ; kinetics ; ageing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary To study the influence of age on the kinetics of atrial natriuretic peptide (ANP) in man, human (99–126) ANP 2.0 μg·min−1 was infused IV for 60 min in 8 healthy young (18 to 25 y) and 9 healthy elderly (71 to 84 y) subjects. Both baseline ANP values and the levels at the end of infusion were higher in the elderly subjects. The mean residence time of ANP in the two age groups was not significantly different, whereas total body clearance (CL) was markedly diminished in the elderly as compared to the young subjects (mean±SD 3.1±1.0 l·min−1 and 6.2±4.1 l·min−1, respectively). The apparent volume of distribution at steady state was lower in the elderly than in the young, but the difference was not significant (mean±SD 44±19 and 103±111, respectively. The decrease in CL largely explained the higher ANP levels found in the elderly subjects. The MRT and the plasma half-life of the terminal phase did not differ between the two groups. In the elderly but not in the young subjects the calculated endogenous creatinine clearance was closely correlated with the CL (r=0.90, P〈0.001), thereby emphasizing the importance of the kidney in the metabolic clearance of ANP in the elderly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00280134
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  • 11
    Electronic Resource
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    Interaction of talinolol and sulfasalazine in the human gastrointestinal tract (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 461-462 
    Details
    ISSN: 1432-1041
    Keywords: Talinolol ; Sulfasalazine ; β-adrenoceptor-blocking drugs ; absorption ; drug interaction ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absorption of talinolol (TA) 50 mg was investigated without and together with the co-administration of sulfasalazine (SASP) 4 g in 11 healthy young volunteers, in order to clarify gastrointestinal transit of TA. Without SASP, the tmax of TA was 2.8 h, Cmax was 112 ng·ml−1 and the half life was 12 h; the AUCo-t was 958 ng·ml−1·h. In the case of concomitant administration of SASP, TA was found only in serum from 3 individuals, with a Cmax of 23 ng·ml−1 and a mean AUCo-t of 84 ng·ml−1·h. TA was not detectable in 5 subjects and it was at the limit of detection (2 ng·ml−1) in 3 subjects. Pharmacokinetic analysis was not possible in any of those individuals. The reason for the interaction appears to be the adsorption of TA by SASP. An interval of 2–3 h should elapse between giving SASP and other drugs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00280137
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  • 12
    Electronic Resource
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    Somewhere between fiction and reality (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 51-70 
    Details
    ISSN: 1572-8943
    Keywords: kinetics ; solid-state reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wurde der Einflu\ verschiedener experimenteller Bedingungen (z.B. Probenmasse, Atmosphäre, Aufheizgeschwindigkeit) auf die Zersetzung von NH4VO3, CaCO3 und V2O5 untersucht. Die Ergebnisse zeigen eindeutig, da\ Reaktionsweg und kinetische Parameter in Wirklichkeit nicht die einzelne Verbindung charakterisieren, sondern eher die Kombination von experimentellen Bedingungen und untersuchter Verbindung. Hierdurch ist es meistens unmöglich, “Standardbedingungen≓ zur Berechnung kinetischer Parameter zu wählen, da unter verschiedenen Umständen ganz andere Reaktionswege beschritten werden können.
    Notes: Abstract The influence of various experimental conditions such as sample weight, atmosphere and heating rate on the decomposition of NH4VO3, CaCO3 and V2O5 has been investigated. Results obtained clearly indicate that the course of the reactions and — in turn — the kinetic parameters, are not intrinsic to the particular compound and that they characterize rather the combination of experimental conditions and investigated compound. Such a situation makes it almost impossible to choose ‘standard conditions’ for the calculation of kinetic parameters, because under different circumstances quite different reaction-pathways can occur.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02109108
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  • 13
    Electronic Resource
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    Possibilities of two non-isothermal procedures (temperature- or rate-controlled) for kinetical studies (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 71-87 
    Details
    ISSN: 1572-8943
    Keywords: CRTA ; kinetics ; TA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wird die Anwendbarkeit von herkömmlicher Thermoanalyse (TA) und geschwindigkeitsgesteuerter Thermoanalyse (CRTA) bei kinetischen Untersuchungen diskutiert. Die TA Technik kann eine zuverlässige kinetische Information und sinnvolle kinetische Parameter besonders bei Feststoffumsetzungen liefern. Die CRTA Technik ist andererseits mehr für Zersetzungsprozesse geeignet, bei denen ein oder mehrere Gase freigesetzt werden. Für beide Techniken wird eine einheitliche und geeignete Methode zu kinetischen Analyse vorgeschlagen. Als Beispiel wird diese Methode zur Analyse des Kristallisationsprozesses von Chalkogenidgläsern sowie der Zersetzung von Dolomit angewendet.
    Notes: Abstract The applicability of both conventional Thermal Analysis (TA) and Controlled Rate Thermal Analysis (CRTA) for kinetic analysis is discussed. It is shown that TA method can give a reliable kinetic information and meaningful kinetic parameters especially for solid state transformation. On the other hand the CRTA method is more suitable for decomposition process where one or more gasses are evolved. A consistent and reliable method of kinetic analysis is proposed for both techniques. This method is illustrated to analyze the crystallization process of chalcogenide glass and the decomposition of dolomite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02109109
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  • 14
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    Thermodynamic and kinetic properties of hydrogen adsorption on thin iron layers (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 1999-2003 
    Details
    ISSN: 1572-8943
    Keywords: calorimetry ; hydrogen adsorption ; kinetics ; thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels kalorimetrischer und volumetrischer Messungen im Temperaturbereich von 298 bis 363 K wurden die thermodynamischen Eigenschaften der Wasserstoffadsorption an Eisenschichten untersucht. Die kinetischen Eigenschaften wurden mit Hilfe der Dekonvulotion kalorimetrischer Thermogramme ermittelt und mit Literaturangaben zum Haftkoeffizienten verglichen.
    Notes: Abstract Thermodynamic properties of hydrogen adsorption on iron layers evaporated under UHV conditions have been determined from calorimetric and volumetric measurements over the temperature range from 298 K to 363 K. Kinetic properties have been determined with the help of deconvolution of calorimetric curves and compared with the literature data on the sticking coefficient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01979610
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  • 15
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    Thermogravimetric analysis of ZnCl2 catalyzed degradation of PVC (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 2349-2357 
    Details
    ISSN: 1572-8943
    Keywords: dehydrochlorination process ; kinetics ; PVC ; ZnCh catalyzed degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels TG wurden die kinetischen Parameter des Dehydrochlorierungsprozesses (DHCL) von PVC und von mit verschiedenen Mengen von ZnCl2 versetztem PVC bestimmt. Diese Werte wurden mit denjenigen verglichen, die man bei der spektroskopischen Analyse der Zersetzung von ZnCl2-haltigen PVC-Filmen bei verschiedenen Temperaturen im sichtbaren UV-Bereich erhalten hatte. Die Werte der scheinbaren Aktivierungsenergie (E a) sinken mit zunehmendem ZnCl2-Gehalt und die hier erhaltenen Werte sind vergleichbar gut mit denen der vorangehenden Arbeit. Der katalytische Effekt von ZnCl2 auf PVC DHCL-Vorgänge wurde erklärt.
    Notes: Abstract The kinetic parameters of dehydrochlorination (DHCL) process of PVC and PVC mixed with different amount of ZnCl2 have been determined by using thermogravimetric analysis. These values have been compared with those obtained by using UV-visible spectroscopic analysis of PVC film containing ZnCh degraded at different temperatures. The values of apparent activation energy (E a) decreases with the increase of the amount of ZnCl2 and the values obtained in the present work are in reasonable comparison with previous works. The catalytic effect of ZnCl2 on PVC DHCL process is explained here.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02123988
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  • 16
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    Isothermal bulk polymerization ofp-alkylaryl methacrylates by DSC (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 709-713 
    Details
    ISSN: 1572-8943
    Keywords: enthalpy of polymerization ; free radical polymerization ; kinetics ; p-alkylphenyl methacrylates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels DSC wurden im Temperaturbereich 348–373 K Reaktionsweg und Kinetik der radikalischen Raumpolymerisation vonp-Alkylphenylmethacrylaten mit AIBN Initiator untersucht. Dabei wurden die Polymerisationsenthalpie, der Monomerrest-gehalt als auch die Geschwindigkeitskonstanten und die Aktivierungsenergien der Gesamt-reaktion bestimmt. Ähnliche Werte für die Gesamtgeschwindigkeitskonstanten weisen darauf hin, daß die relativ kleinen Alkylsubstituenten inp-Stellung des Phenylringes die Polymerisationsgeschwindigkeit nur in sehr kleinem Maße — wenn überhaupt — beeinflussen.
    Notes: Abstract The course and kinetics of free radical polymerization in bulk ofp-alkylphenyl methacrylates with AIBN initiator were studied by DSC, in the temperature range 348–373 K. The enthalpy of polymerization, the residual monomer content, as well as the overall reaction rate constants and the activation energies were determined. The similar values of the overall rate constants indicate that the relatively small alkyl substituents inp-position of the phenyl ring affect the polymerization rate to a very small, if any, extent.
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    URL: http://dx.doi.org/10.1007/BF01979400
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  • 17
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    The determination of a complex kinetic expression of oil shale pyrolysis using combined non-isothermal and isothermal TG (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 729-738 
    Details
    ISSN: 1572-8943
    Keywords: kinetics ; oil shale pyrolysis ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die im allgemeinen benutzte Kinetikgleichung in der Thermoanalyse von Ölschieferpyrolyse wurde auf der Grundlage einer einfachen kinetischen Gleichung erster Ordnung der Kerogenzersetzung erhalten. Mittels nichtisothermer (NI) oder isothermer (I) TG kann sowohl die Aktivierungsenergie als auch die Reaktionsgeschwindigkeitskonstante der Ölschieferpyrolyse bestimmt werden. Die unter Anwendung von NI oder I ermittelten kinetischen Parameter ermöglichen jedoch keine gute Voraussage des Kerogenumsatzes bei anderen Bedingungen. Es werden hier die Vergleichsergebnisse aus NI- bzw. I-TG von verschiedenen Ölschiefern als auch die Auswirkungen auf die sogenannte kombinierte nichtisotherme und isotherme TG (NI/I) besprochen. Die erhaltenen Ergebnisse zeigen, daß ein Mechanismus angenommen werden muß, der auf einem komplexen Reaktionsschema aus mehr als aus einer einfachen Reaktion basiert.
    Notes: Abstract The kinetic expression commonly used in the thermal analysis of oil shale pyrolysis was derived on the basis of a simple first order kinetic equation of kerogen decomposition. The activation energy, as well as the reaction rate constant of oil shale pyrolysis could be determined by using non-isothermal (NI) or isothermal (I) TG. However, the kinetic parameters determined by using either NI or I did not enable the good prediction of the kerogen conversion at other conditions. The comparative results of the NI and I-TG of different oil shales are discussed in the study, as well as the effects of the so-called combined non-isothermal and isothermal TG (NI/I). The obtained results indicate that a mechanism must be postulated based on a complex reaction scheme which involves more than one simple reaction.
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    URL: http://dx.doi.org/10.1007/BF01979403
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  • 18
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    On the maximum reaction rate and inflexion points on the DTG curve (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 721-728 
    Details
    ISSN: 1572-8943
    Keywords: kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es werden einige theoretische Überlegungen bezüglich des Einflusses der Form der Konversionsfunktionf(α) auf die Werte der Konversionsrate bei maximalen Reaktionsgeschwindigkeiten (αmax) sowie auf Inflexionspunkte (α∞) der DTG-Kurve angestellt. Die erhaltenen Gleichungen sind unabhängig von der Form vonf(α) durch eine all-gemeine Gültigkeit charakterisiert.
    Notes: Abstract The authors present some theoretical considerations concerning the influence of the form of the conversion functionf(α) on the values of the degree of conversion corresponding to the maximum value of the reaction rate (αmax) as well as on the inflexion points (αinf) of the DTG curve. The obtained equations are characterized by a general validity no matter the form off(α).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01979402
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  • 19
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    The effect of water vapour pressure on the thermal dehydration of yttrium formate dihydrate (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 1793-1799 
    Details
    ISSN: 1572-8943
    Keywords: hydrated salts ; kinetics ; thermal dehydration ; yttrium formate dihydrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels isothermer Gravimetrie und bei verschiedenen Wasserdampfdrücken zwischen 5×10−4 und 8 Torr wurde die Kinetik der thermischen Dehydratation von Yttriumformiat-Dihydrat untersucht. Die Dehydratation wird als dreidimensionale Phasengrenzreaktion R3 beschrieben. Dabei wurde ein ungewöhnlicher Einfluß des athmosphärischen Wasserdampfdruckes auf die Dehydratationsgesch windigkeit beobachtet: mit steigendem Wasserdampfdruck wächst die Geschwindigkeit zunächst ebenfalls an, durchquert ein Maximum und sinkt dann nach und nach auf einen konstanten Wert ab. Diese Erscheinung ähnelt dem Smith-Topley-Effekt. Der Mechanismus dieser Erscheinung kann auf der Grundlage der Kristallinität der dehydratierten Produktephase diskutiert werden.
    Notes: Abstract The kinetics of the thermal dehydration of yttrium formate dihydrate was studied by means of isothermal gravimetry under various water vapour pressures from 5×10−4 to 8 torr. On the whole, the dehydration was described as the three dimensional phase boundary reaction, R3. An unusual dependence of the rate of dehydration on the atmospheric water vapour pressure was observed: with increasing water vapour pressure, the rate increased at first, passed through a maximum, and then decreased gradually to a constant value. These phenomena were similar to the Smith-Topley effect. The mechanism of the phenomena can be described on the basis of the crystallinity of the dehydrated product phase.
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    URL: http://dx.doi.org/10.1007/BF01974674
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    Flash calcination of kaolinite studied by DSC, TG and MAS NMR (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 2053-2065 
    Details
    ISSN: 1572-8943
    Keywords: calcination ; high temperature reactions ; kaolinite ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Strukturelle Veränderungen bei der Dehydroxylierung von Kaolinit wurden durch die Anwendung einer Blitz-Kalzination untersucht, um kinetisch eingefrorene Kalzinationsprodukte zu erhalten. Der Prozentsatz der Dehydroxylierung wurde durch Veränderung der Verweilzeit im Ofen, durch Ofentemperatur und/oder Heizgeschwindigkeit modifiziert. Diese Kalzinationsbedingungen beeinflußten zwar die Reaktionskinetik, aber die Produkte hingen nur vom Ausmaß der Dehydroxylierung ab. Abweichungen bei Lage und Enthalpie der endothermen Umwandlung zu Metakaolinit und die exotherme Hochtemperaturreaktion von Metakaolinit wurden mittels DSC der Blitz-Kalzinationsprodukte verfolgt und in Beziehung zur Thermogravimetrie gebracht. 27Al Magic-Angle-Spinning NMR Spektren bei hohen magnetischen Feldstärken und Drehgeschwindigkeiten erlauben es, die Reaktion von Kaolinit zu verfolgen und liefern neue Informationen über die Natur der bei der Dehydroxylierung gebildeten Substanzen.
    Notes: Abstract The structural changes occurring during the dehydroxylation of kaolinite have been followed using flash calcination to produce kinetically frozen calcines. The percentage of dehydroxylation was varied by changing the furnace residence time or temperature and/or heating speed. These calcination conditions affected the reaction kinetics, but the products depended only on the extent of dehydroxylation. Changes in the position and enthalpy of the endothermic transformation to metakaolinite and the high temperature exothermic reaction of metakaolinite have been followed using Differential Scanning Calorimetry of the flash calcines and related to Thermogravimetry. 27Al magic-angle-spinning NMR spectra, at high magnetic fields and spin rates, enabled the reaction of kaolinite to be monitored and provides new information on the nature of the species formed in the course of dehydration.
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    Simultaneous thermal analyses for thermal dissociation studies on ZrO2 (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 2129-2135 
    Details
    ISSN: 1572-8943
    Keywords: kinetics ; thermal dissociation ; ZrO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Im Temperaturintervall von 300 K bis 2670 K wurde im Hochvakuum und bei verschiedenen Aufheizgeschwindigkeiten das thermische Verhalten von Zirkoniumoxid ZrO2 untersucht. Die Experimente wurden mit Hilfe eines schweizer Universal Mettler Thermoanalysators, ausgerüstet mit einem SHT Super-Hochtemperatur-Ofen, ausgeführt. Flüchtige Produkte wurden simultan dazu mit einem Massenspektrometer QMG-101 der Balzers-Company analysiert. Die Auswertung der durch aufgezeichneten TG-, DTG-, DTA- und EGA-Kurven zeigt den komplexen Charakter des untersuchten Prozesses. Die Elementarschritte der Gesamtreaktion wurden definiert und berücksichtigt. Weiterhin wurde der Mechanismus der Thermodissoziation von ZrO2 auch in Abhängigkeit von der Aufheizgeschwindigkeit diskutiert.
    Notes: Abstract The behaviour of zirconium oxide ZrO2 during its heating in the temperature range 300–2670 K under high-vacuum conditions and at different heating rates has been studied. The experiments were performed with a Swiss made Universal Mettler thermoanalyser equipped with a super-high-temperature furnace SHT. Volatile products were analyzed simultaneously by means of a Balzers QMG-101 mass spectrometer. An analysis of the TG, DTG, DTA and EGA curves recorded simultaneously has shown the complex character of the studied process. The elementary steps of the overall process were defined and taken into consideration. The mechanism of the thermal dissociation reaction of ZrO2 as function of the hearing rate was discussed too.
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    Lattice energy of organic ionic crystals and its importance in analysis of features, behaviour and reactivity of solid-state systems (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 2195-2210 
    Details
    ISSN: 1572-8943
    Keywords: kinetics ; lattice energy ; solid-state systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wird eine allgemeine Methode zur theoretischen Ableitung der Kristallgitterenergie von ionischen Verbindungen, insbesondere von Verbindungen mit einatomigen Ionen beschrieben. Anschließend werden die Möglichkeiten einer theoretischen Voraussage der Gitterenergie komplexer organischer und anorganischer Ionenverbindungen diskutiert. Zuletzt wird die Bedeutung der Gitterenergie bei der Untersuchung der Eigenschaften und des Verhaltens von Feststoffsystemen im Zusammenhang mit der Aussicht auf die Entwicklung eines Modelles zur Beschreibung der Kinetik von Feststoffprozessen gezeigt.
    Notes: Abstract A general approach to the theoretical evaluation of the crystal lattice energy of ionic substances, particularly those composed of monoatomic ions, is outlined in detail. Subsequently, the possibilities of theoretical prediction of the lattice energy of complex organic and inorganic ionic substances are discussed. Lastly, the importance of the lattice energy in examinations of the properties and behaviour of solid-state systems, is treated, together with the prospects of developing a model describing the kinetics of solid-state processes.
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    Zersetzung von Phosphor-Rohrstoffen durch Säuren (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 1683-1690 
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    ISSN: 1572-8943
    Keywords: kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Auf Grund der bestimmten thermokinetischen Kurven der Zersetzung von Phosphor-Rohstoffen mit Säuren wurde die Abhängigkeit des Umwandlunsgrades der einzelnen Reagenten von solchen Faktoren wie Zeit, Enthalpie u. konstante Zerlegungeschwindigkeit bestimmt.
    Notes: Abstract On the basis of the thermokinetic curves of the phosphor deposits with acids the dependence of the conversion degree upon the time, the enthalpy and the reaction rate constant were determined.
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    URL: http://dx.doi.org/10.1007/BF01979364
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    Role of heat and gas transport processes in thermal analysis (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 197-211 
    Details
    ISSN: 1572-8943
    Keywords: gas/heat transport ; kinetics ; quasi static-methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Beim Verlauf von Feststoffreaktionen spielen Wärme- und Gastransport eine wesentliche Rolle. Eine Standardisierung der experimentellen Bedingungen wäre deshalb erforderlich, was jedoch bisher nur bezüglich der Erarbeitung von Simultantechniken gelang. Au\erdem sind diese beiden Transportprozesse dafür verantwortlich, da\ man ausgehend von nichtisothermen Kurven keine kinetischen Parameter berechnen kenn. Quasistatische Methoden scheinen geeignet zu sein, um den störenden Einflu\ dieser Transportprozesse zu eliminieren.
    Notes: Abstract In the course of solid phase reactions heat and gas transport processes play a dominant role. Therefore, it would be necessary to standardize the experimental conditions which succeeded only in part with the elaboration of the simultaneous techniques. Likewise the two transport processes are responsible for the fact that on the basis of non-isothermal curves one cannot calculate kinetic parameters of the reactions. The quasi static-methods seem to be suitable for the elimination of the pernicious effect of these transport processes.
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    URL: http://dx.doi.org/10.1007/BF02109119
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    Derivatographic investigations of polycarbonates (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 2211-2219 
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    ISSN: 1572-8943
    Keywords: kinetics ; polycarbonates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Derivatographische, nichtisotherme Untersuchungen der Zersetzung von Polycarbonaten in Luft liefern nutzbringende Informationen über die charakteristischen Zersetzungstemperaturen und die scheinbaren Aktivierungsenergien der untersuchten Zersetzungsschritte. Dabei wurde folgende Reihenfolge der scheinbaren Aktivierungsenergie der Pyrolyseschritte beobachtet: PC-M PC-C PC-A. Wegen der Abschirmung der Esterketten durch ortho-Methylsubstituenten sind die Werte E für PC-M am höchsten.
    Notes: Abstract Derivatographic non-isothermal investigations of the decomposition of PC in air provide useful information on the characteristic decomposition temperatures and the apparent activation energies of the observed steps of decomposition. The following sequence of apparent activation energies of the pyrolysis step was obtained: PC-M〉PC-C〉PC-A. The values ofE for PC-M are the highest, due to shielding of the ester linkages by the ortho-methyl substituents.
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    Kinetics of isothermal decomposition of γ-irradiated and unirradiated Co(II) succinato complex (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 2377-2383 
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    ISSN: 1572-8943
    Keywords: Co(II) succinate complex ; isothermal decomposition ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Unter Anwendung von isothermen und dynamischen thermogravimetrischen Methoden wurde eine kinetische Untersuchung der Dehydratation und der Zersetzung von γ-bestrahltem und unbestrahltem Na2[Co(C4H4O4)2]·7H2O durchgeführt. Die thermische Dehydratation erfolgt in einem Schritt, bestimmt durch ein Random-Keimbildungsmodell (A3), während die Zersetzung der wasserfreien Salze durch ein phasengrenzenkontrolliertes Modell bestimmt wird (R3). Die bei drei Aufheizgeschwindigkeiten erhaltenen kinetischen Parameter stehen in guter Übereinstimmung; jedoch weichen die isotherm geschätzten kinetischen Parameter etwas von den dynamisch ermittelten ab. Bestrahlung mehrt sowohl die Dehydratations- als auch die Zersetzungsreaktionen, beläßt deren Mechanismus jedoch unverändert. Die Aktivierungsenergie sinkt mit zunehmender Strahlungsdosis.
    Notes: Abstract A kinetic study of the dehydration and decomposition of γ-irradiated and unirradiated Na2[Co(C4H4O4)2]·7H2O has been studied using isothermal and dynamic thermogravimetric methods. The thermal dehydration occurs in one step regulated by a random nucleation model (A3), while the decomposition of anhydrous salt is controlled by a phase boundary controlled model (R3). The kinetic parameters obtained at three heating rates are in good agreement; however, the values of the kinetic parameters estimated isothermally are slightly different from those estimated dynamically. Irradiation enhanced both the dehydration and the decomposition reactions but did not modify their mechanisms. The activation energy decreases as the irradiation dose increases.
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    On the fractional conversion α in the kinetic description of solid-state reactions (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 2553-2557 
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    ISSN: 1572-8943
    Keywords: kinetics ; solid-state reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract For the kinetic description of the solid-state reactions, the dependence of the apparent kinetic parameters on the sample mass and/or particle size is discussed mathematically in relation to some problems on the fractional conversion a. As for the reaction proceeding according to the contracting geometry model, the use of the specific rate constant, independent of the sample mass and particle size, is recommended to obtain the sample mass-independent Arrhenius parameters. It is also pointed out that the distribution of α within the assembly of sample particles disturbs the successful use of α in the kinetic description of the solid-state reactions.
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    URL: http://dx.doi.org/10.1007/BF01974632
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    Kinetic study of surface nucleated MgO-CaO-Al2O3-SiO2 glasses (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 2639-2647 
    Details
    ISSN: 1572-8943
    Keywords: kinetics ; MgO-CaO-Al2O3-SiO2 glasses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Vorliegende Arbeit untersucht mittels thermoanalytischen Untersuchungen die Berechtigung von drei verschiedenen Methoden zur Ermittlung der Aktivierungsenergie der Kristallisation bei Gläsern mit Oberflächen-Kristallisationskeimen im System MgO-CaO-Al2O3-SiO2, wobei Anorthit- und Diopsidkristalle ausgeschieden werden. Die anhand der Kissinger-Gleichung erhaltenen Werte für die Aktivierungsenergie der Kristallisation sind vergleichbar mit denen, die von anderen Autoren für ähnliche Glassysteme erhalten wurden: 90–150 kcal/mol. Die Ergebnisse der kinetischen Analyse mittels der Einfach-Kristallisationspeak Methode sollten korrigiert werden, indem man die Dimensionalität des Kristallwachstums berücksichtigt.
    Notes: Abstract The paper investigated, by means of thermal analysis measurements, the validity of three different methods for the evaluation of the activation energy of crystallization for surface nucleated glasses belonging to the MgO-CaO-Al2O3-SiO2 system, separating anorthite and diopside crystals. The values obtained from Kissinger equation of the activation energy for crystallization are comparable with those obtained by other authors for similar glassy systems, 90 to 150 kcal/mol. The results of the kinetic analysis using single-crystallization-peak method should be corrected taking into account the dimensionality of crystal growth.
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    URL: http://dx.doi.org/10.1007/BF01979740
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    Thermal analysis and kinetic study of decomposition processes of some pesticides (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 2669-2682 
    Details
    ISSN: 1572-8943
    Keywords: kinetics ; pesticides ; thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels simultanen TG-DSC-Messungen und kinetischen Berechnungen bei der DTG-Technik wurde eine thermische Analyse einiger Pestizide durchgeführt. Mit dieser Methode wurde versucht, Verbindungen mit ähnlichen Strukturen anhand der Form und Anzahl von Peaks ihrer thermoanalytischen Kurven zu gruppieren und ihre Eigenschaften mittels thermodynamischen und kinetischen Mengen zu charakterisieren. Geringe Änderungen in der Struktur der Komponenten einer Klasse verursachen größere Veränderungen der thermodynamischen und kinetischen Größen, was in enger Übereinstimmung mit den beobachteten Unterschieden ihrer biologischen Aktivität steht.
    Notes: Abstract The thermal analysis of some pesticides using simultaneous TG-DSC measurements and kinetic calculations by the dynamic TG technique have been carried out. With this technique it was attempted to group compounds with similar structures according to the shape and number of peaks of their thermoanalytical curves and to characterize their features by means of thermodynamic and kinetic quantities. Small variations in the structure of the components of a class make larger variations in the thermodynamic and kinetic values being in close agreement with the observed differences in their biological behaviour.
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    The thermal degradation kinetics of poly(chlorethylmethacrylates) (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 267-275 
    Details
    ISSN: 1572-8943
    Keywords: kinetics ; poly(chlorethyl methacrylates)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels TG wurde in Gegenwart und in Abwesenheit von Sauerstoff die Kinetik des thermischen Abbaues von Poly(2-mono, 2,2-di- und 2,2,2-trichlorethylmethacrylat) und des nichtchlorierten Poly(ethylmethacrylat) untersucht. Die mit der Flynn-Wall Methode bestimmte Gesamtenergie des thermischen Abbaues steigt mit wachsendem Chlorgehalt des Polymers, wenn der Abbau ohne Sauerstoff erfolgt. In Gegenwart von Sauerstoff wird dieser Trend genau umgekehrt. Mittels DTG konnten die zwei wichtigsten nichtoxidativen Thermolysereaktionen, Depolymerisierung und Vernetzung, als kompetitive Reaktionen nachgewiesen werden. Ganz allgemein wird die thermische Stabilität der untersuchten Polymere durch Sauerstoff herabgesetzt.
    Notes: Abstract The thermal degradation kinetics of poly(2-mono-, 2,2-di- and 2,2,2-trichlorethyl methacrylate) and of the non-chlorinated poly(ethyl methacrylate) were studied by TG in the absence and presence of oxygen. The overall thermal degradation energy, determined by the Flynn-Wall method, increases with increasing chlorine content of the polymer when the degradation is performed in the absence of oxygen, while the trend is reversed in the presence of oxygen. Competition between the two major non-oxidative thermolysis reactions, depolymerization and crosslinking, could be monitored by DTG. Generally, the thermal stability of the investigated polymers is reduced by oxygen.
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    High-speed versatile device for investigating thermal decomposition processes (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 391-396 
    Details
    ISSN: 1572-8943
    Keywords: intensive heating and cooling method and technique ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wird eine neue Methode und ein neues Verfahren von thermoanalytischen Versuchen zur Untersuchung thermischer Zersetzungsprozesse sowie auch zur Bestimmung kinetischer und thermophysikalischer Eigenschaften von Feststoffen und Flüssigkeiten bei intensivem Erhitzen oder Abkühlen beschrieben.
    Notes: Abstract A new method and technique of TA-experiment are suggested for investigating thermal decomposition processes, as well as for determining kinetic and thermophysical characteristics of solid and liquid substances under conditions of intensive heating or cooling.
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    URL: http://dx.doi.org/10.1007/BF01915503
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    A kinetic study of water evolution from a molten hydrated salt (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 421-428 
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    ISSN: 1572-8943
    Keywords: kinetics ; meso lithium potassium tartrate dihydrate ; molten hydrated salt
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Meso-Lithiumkaliumtartrat-Dihydrat schmilzt noch vor der Dehydratation, eine kinetische Untersuchung dieser Reaktion wurde vollzogen. Dieses System ist interessant für die Abschätzung kinetischer Parameter von Prozessen mit gleichbleibender Geschwindigkeit ohne Gegenwart zugesetzter Lösungsmittel. Die Ergebnisse sind von Interesse bei überlegungen zu Mechanismen von Feststoffreaktionen oder Reaktionen im kondensierten Zustand, bei denen Schmelzen als Möglichkeit auftritt. Die Freisetzung der ersten 1.2 H2O aus den Einkristall-Dihydratreaktanden ist eine Reaktion nullter Ordnung, anschlie\end wird die Geschwindigkeit verlangsamt und unterliegt bis 1.6 H2O einem Ausdruck erster Ordnung. Der Vorgang weist eine hohe Aktivierungsenergie auf: 23010 kJ/mol (bei 350–380 K). Die Freisetzung des restlichen Wassers erfolgt in einer langsameren Reaktion erster Ordnung, man erhält das wasserfreie Salz. Die Dehydratation von zerkleinerten pulverisierten Reaktanden verlief anfangs relativ schneller, verlangsamt dann jedoch ganz und gar und unterliegt einer ersten Reaktionsordnung. Es wird geschlu\folgert, da\ die Dehydratation des Salzes durch die Freisetzungsgeschwindigkeit des Wassers an der Oberfläche kontrolliert wird, wobei das Wasser innerhalb der Reaktionsschmelze relativ beweglich ist.
    Notes: Abstract Meso lithium potassium tartrate dihydrate melted before dehydration and a kinetic study of this reaction has been completed. This system is of interest in establishing the kinetic characteristics of a homogeneous rate process in the absence of added solvent. Results are of interest in considering the mechanisms of solid or condensed state reactions where melting is a possibility. The evolution of the initial 1.2H2O from the single crystal dihydrate reactants was zero order, the rate then became deceleratory and the first order expression was obeyed to 1.6H2O. The activation energy of the process was high, 230±10 kJ mol−1 (350–380 K). Evolution of the remaining water occurred by a slower first-order process to give the anhydrous salt. The dehydration of crushed powder reactant was initially relatively more rapid but was deceleratory throughout, obeying the first order equation. It is concluded that salt dehydration is controlled by the rate of surface release of water that is comparatively mobile within the reactant melt.
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    Significance of the kinetics of thermal decomposition of NaHCO3 evaluated by thermal analysis (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 429-435 
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    ISSN: 1572-8943
    Keywords: compensation effect ; experimental conditions ; kinetics ; NaHCO3 ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels TG wurden sowohl bei konstanter als auch bei linear ansteigender Temperatur die Arrheniusschen Konstanten und das Kinetikgesetz der thermischen Zersetzung von Natriumhydrogencarbonat bestimmt. Dabei wurde der Einflu\ der Probengrö\e (0.5–10mg) und der Partikelgrö\e auf das Geschwindigkeitsverhalten untersucht. Mit Proben kleiner als etwa 5 mg ist der Einflu\ der Aufheizgeschwindigkeit nicht so gro\, wie bei grö\eren Proben. Die ermittelten Arrheniusschen Parameter und das ermittelte Kinetikgesetz, bestimmt mittels der Methode von Ozawa, stehen in ausgezeichneter übereinstimmung mit den isotherm ermittelten Resultaten. Die Aktivierungsenergie E bei einer Probe mit einer Masse von etwa 1 mg war nahezu konstant, unabhängig vom Reaktionsgrad. Jede änderung des Arrheniusschen Parameters infolge von veränderten Versuchsbedingungen wurde in Verbindung mit dem kinetischen Kompensationseffekt diskutiert.
    Notes: Abstract The Arrhenius parameters and kinetic obedience were determined by TG at constant temperatures as well as at linearly increasing temperatures for the thermal decomposition of sodium hydrogencarbonate. Effects of the sample size (0.5–10 mg) and the particle size on the rate behavior were examined. With such a sample size smaller than ca. 5 mg, an effect of the heating rate was not so critical as is the case with the larger sample size. The Arrhenius parameters and kinetic obedience determined by use of the Ozawa method were in excellent agreement with those determined isothermally. The activation energyE determined with ca. 1 mg of sample was nearly constant independently of the fractional reactiona. Any change in the Arrhenius parameters with different experimental conditions was dicussed in connection with the kinetic compensation effect.
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    Factors affecting the experimentally resolved shapes of TG curves (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 575-582 
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    ISSN: 1572-8943
    Keywords: kinetics ; shapes of TG curves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Unter theoretischen Aspekten bezüglich derjenigen Faktoren, die die experimentelle Auflösung thermogravimetrischer Kurven beeinflussen, wird ein möglicher Weg zur Steigerung der Genauigkeit thermogravimetrischer Untersuchungen diskutiert.
    Notes: Abstract From a theoretical consideration concerning the factors affecting the experimentally resolved shapes of thermogravimetric curves, the possible way to increase the accuracy of the thermogravimetric measurements were discussed.
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    Modelling of diffusion-controlled solid-solid reactions (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 935-941 
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    ISSN: 1572-8943
    Keywords: kinetics ; solid-solid reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wird ein Modell zur Beschreibung des einleitenden Schrittes von diffusionskontrollierten Feststoffreaktionen beschrieben. Die erhaltene kinetische Gleichung wurde zur Bestimmung der Aktivierungsenergie der Reaktion LiCl(s) + NaF(s)=LiF(s) + NaCl(s) aus DTA-Daten angewendet.
    Notes: Abstract A model describing the initial step of diffusion-controlled solid-solid reactions is presented. The kinetic equation obtained was used to evaluate the activation energy of the reaction LiCl(s)+NaF(s)=LiF(s)+NaCl(s) from DTA data.
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    A comparison of some integral methods (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 929-933 
    Details
    ISSN: 1572-8943
    Keywords: integral methods ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Integrationsmethoden zur Berechnung kinetischer Parameter von heterogenen Reaktionen unter nicht isothermen Bedingungen werden im allgemeinen nach der Methode der kleinsten Quadrate erarbeitet und der ermittelte Korrelationskoeffizient dient als ein Kriterium für die Auswahl der besten Integrationsmethode. Mittels drei verschiedenen Integrationsmethoden wurde eine Analyse verschiedener experimenteller Daten durchgeführt. Die Ergebnisse zeigen, daß dieses Kriterium allein nicht ausreicht, um ausreichende Informationen über die kinetischen Parameter zu liefern. Es scheint deshalb, daß die Verwendung der einen oder anderen Integrationsmethode einfach eine Wahl des Anwenders darstellt.
    Notes: Abstract The integral methods proposed to compute the kinetic parameters of heterogeneous reactions under non-isothermal conditions are usually worked by the help of the least squares method and the obtained correlation coefficient is taken as a criterion to choose the best integral method. An analysis of several experimental data by mean of three different integral methods was performed by us and the results pointed out that this criterion, by itself, is not enough to provide reliable information on the kinetic parameters. It appears, thus, that the use of an integral method or another is a simple matter of researcher's choice.
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    The thermal degradation kinetics of poly(di-n-alkylitaconates) (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 953-959 
    Details
    ISSN: 1572-8943
    Keywords: kinetics ; poly(di-n-alkyl itaconates) ; thermal stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels nichtisothermer und auch isothermer TG wurde die nichtoxidative thermische Zersetzungskinetik von Poly(di-n-alkylitakonaten) untersucht, dabei bewegt sich die Länge der Alkylkette von Methyl bisn-Oktyl. Die Aktivierungsenergie der thermischen Zersetzung und die charakteristischen Masseverlusttemperaturen nehmen mit steigender Substituentlänge ab. Aussehen der DTG-Kurven hängt von der Größe der Alkylkette ab. Die verschiedenen DTG-Maxima wurden verschiedenen Initiierungs schritten der Depolymerisierung zugeschrieben. Man fand, daß im Intervall Mw zwischen 104 und 107 g·mol die thermische Stabilität der Poly(di-n-hexylitakonate) unabhängig von der anfänglichen molaren Masse der Probe ist.
    Notes: Abstract The non-oxidative thermal degradation kinetics of poly(di-n-alkyl itaconates), ranging from the methyl to then-octyl derivatives, were studied by non-isothermal and isothermal TG. The thermal degradation activation energy and characteristic mass loss temperatures were found to decrease with increasing substituent size. The shapes of the DTG curves were dependent on the size of the alkyl substituent. The different DTG maxima were ascribed to various modes of initiation of depolymerisation. The thermal stability of poly(di-n-hexyl itaconate) was found to be independent of the initial molar mass of the sample in the range ofM w from 104 to 107 g/mol.
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    Rapid thermal analysis of processes of thermal decomposition of mineral salts (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 981-988 
    Details
    ISSN: 1572-8943
    Keywords: kinetics ; mineral salts ; rapid TA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Für thermische Zersetzung und Synthese von Mineralsalzen wurden die kinetischen Kurven unter den Bedingungen schnellen Aufheizens in Annäherung der Aufheizbedingungen in einem Niedertemperatur-Plasmastrom ermittelt. Die kinetischen Eigenschaften wurden zur Berechnung der Umwandlungen bei einem chemischen Plasmareaktor verwendet.
    Notes: Abstract Kinetic curves of thermal decomposition and synthesis of mineral salts are obtained in the conditions of rapid heating approaching the heating conditions in a low-temperature plasma flow. The kinetic characteristics are used in calculations of transformations in the path of a chemical plasma reactor.
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    Different kinetic equations analysis (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 1509-1524 
    Details
    ISSN: 1572-8943
    Keywords: kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Cu(II)-komplexe von Acenaphthoquinonmono-(4-methyl-quinolinyl)-hydrazon (AMH) der allgemeinen Zusammensetzung [CuLX2] (mitL=AMH;X=Cl, Br, I, OAc oder NO3) -ausgenommen die Sulfato-komplexe, die über die allgemeine Zusammensetzung [CuLSO4]2 verfügen — wurden hergestellt und mittels Elementaranalyse, Messungen des magnetischen Momentes, Leitfähigkeitsmessungen, IR, elektronen- und EPR-spektroskopischen Techniken und durch Thermoanalyse untersucht. Für alle Komplexe wurde eine planare Geometrie gefunden. Die TG-Kurven zeigen, daß die Komplexe in einem Schritt zersetzt werden, wobei am Ende dieses Schrittes CU2O gebildet wird.
    Notes: Abstract A software is described enabling kinetic analysis under non-isothermal or isothermal conditions from DSC, or from TG data. The program offers thirteen methods of kinetic analysis for DSC, three for isothermal analysis and two for TG, with eight different functions for the choice of the proper mechanism for each of them.
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    Computer simulation of thermal analysis in heat-flux DSC applied to metal solidification (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 1949-1957 
    Details
    ISSN: 1572-8943
    Keywords: alloys ; heat-flux differential scanning calorimetry ; kinetics ; metals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wird ein allgemeine mathematische Behandlung von Wärmefluß-DSC gegeben. Es verbindet Gleichungen für den Wärmetransport in der Kalorimeterzelle mit einer Annäherung der Verfestigung von Metall oder Legierung, die in diesem Gerätetyp durchgeführt werden. Es werden die Unterschiede zwischen: Temperaturevolution, Kinetik latenter Wärme und Unterkühlungsevolution innerhalb der Probe und zwischen: Temperaturevolution, aufgezeichnetes Signal und gemessene Unterkühlung an der Monitorstation diskutiert.
    Notes: Abstract A general mathematical treatment for heat-flux differential scanning calorimetry is given. It combines equations derived for heat transfer in the calorimeter cell with an approach to the solidification of metal or alloy carried out in this type of instrument. The differences are discussed between temperature evolution, kinetics of latent heat and undercooling evolution within the sample, and temperature evolution, recorded signal and measured undercooling at the monitoring station.
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    Flow-microcalorimetric determination of enzymatic activities of the Trichoderma viridae-cellulase complex (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 1979-1988 
    Details
    ISSN: 1572-8943
    Keywords: cellulase complex ; enzymatic activities ; flow-microcalorimetryl ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wird eine Methode zur Bestimmung der enzymatischen Aktivität des Trichoderma viridae Zellulase Komplexes beschrieben. Dazu wurde ein LKB 2277 Thermoaktivitätsmonitor und ein kontinuierlicher Flüsigkeitsmischer verwendet. Bei der Bestimmung der enzymatischen Aktivität von Proben des rohen Zellulasekomplexes wurden drei Substanzen verwendet: Zellobiose, Karboxymethylzellulose (CMC) und Hemizellulose. Anhand der Ergebnisse wurden einige kinetische Parameter für die Zellobiaseaktivität ermittelt. Außerdem wurde eine Endprodukt-Inhibition von Zellobiase sowie Karboxymethylzellulaseaktivität durch Glukose beobachtet. Das beschriebene Verfahren erlaubt eine direkte Bestimmung der verschiedenen Enzymaktivitäten des Zellulasekomplexes. Wegen ihrer hohen Empfindlichkeit und Einfachheit handelt es sich hier um ein sehr nützliches Werkzeug zur Untersuchung des Zellulasekomplexes, indem die optimalen Bedingungen für die enzymatische Spaltung zelluloser Substanzen bestimmt und verschiedene Mechanismen von Feedback-Kontrolle durch die Produkte der Enzymtätigkeit beobachtet werden. Das Verfahren trägt vollkommen allgemeinen Charakter und kann auch bei anderen Ezymsystemen Anwendung finden.
    Notes: Abstract A method for measuring enzymatic activities of the Trichoderma viridae cellulase complex is described. The LKB 2277 Thermal activity monitor and a flow-mix mode were used. Enzymatic activities of samples of a crude cellulose complex have been determined using three substrates: cellobiose, carboxymethyl cellulose (CMC) and xylan. Some kinetic constants for cellobiase activity have been evaluated from the obtained results. A process of the end-product inhibition of cellobiase resp. carboxymethyl cellulase activity by glucose has been observed too. The described method allows a direct determination of various enzymatic activities of the cellulase complex. Because of the high sensitivity and the simplicity, the method is a very suitable tool for studying the cellulase complex, determining the optimal conditions of enzymatic break-down of the cellulosic materials and observing various mechanisms of the feed-back control by products of enzymatic action. The procedure is completely general in nature and is applicable to other enzymatic systems.
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    Oxide particles in Ag-Mg alloys formed by internal oxidation (1992)
    Springer
    Oxidation of metals 37 (1992), S. 65-80 
    Details
    ISSN: 1573-4889
    Keywords: internal oxidation ; kinetics ; alloys ; silver ; oxide particles ; coalescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Gravimetric measurements at low temperatures (〈600°C) and for dilute Ag-Mg alloys have given further information about the mechanism of oxide formation. This investigation shows that the fixation rate of oxygen is very high, which assumes the existence of species in an oxidized form, including one or two magnesium atoms called “elementary species” and denoted as MgO* and Mg2O*. When there are no free magnesium atoms, there is a coalescence process with the fixation of oxygen atoms or MgO* and Mg2O*: this process leads to the formation of the first “clusters” including an oxygen excess. At low temperatures, the thermal fluctuations do not permit significant changes. There is no significant increase in cluster size, but a rearrangement of these clusters toward a compact structure with the release of excess oxygen. Their size is less than 1 nm.
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    High-temperature oxidation of zirconium-hydride powders (1992)
    Springer
    Oxidation of metals 38 (1992), S. 89-98 
    Details
    ISSN: 1573-4889
    Keywords: kinetics ; oxidation ; zirconium hydride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation kinetics of zirconium-hydride powders were studied in the temperature range of 298–1378 in air at atmospheric pressure. TG, DTA, DSC, x-ray analysis, and scanning electron microscopy were used. The results obtained are in accordance with the proposed pseudo-parabolic model of zirconium-hydride oxidation. This model includes the initial linear mode of oxide growth with oxygen diffusion through a non-solid film of ZrO2 of variable depth and a stationary diffusion process followed by oxide sintering. It has been established that the activation energy of the limiting stage of oxidation (238.3 kJ/mol) coincides with the activation energy of oxygen self-diffusion in monocline ZrO2.
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    Kinetics and mechanism of high-temperature sulfidation of an Fe-23.4Cr-18.6Al Alloy in H2S-H2 atmospheres (1992)
    Springer
    Oxidation of metals 38 (1992), S. 1-32 
    Details
    ISSN: 1573-4889
    Keywords: sulfidation ; Fe-Cr-Al alloys ; kinetics ; structures ; sulfide compositions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Sulfidation of an Fe-23.4Cr-18.6Al (at.%) alloy was investigated in H2S-H2 atmospheres, $$10^{ - 6} \leqslant {\text{P}}_{{\text{S}}_{\text{2}} } \leqslant 10^2 $$ Pa, at 973 K. It was found over this pressure range that sulfidation after an early transient period followed the parabolic rate law, being diffusion controlled. An investigation was carried out of the scales formed during early transient sulfidation over the sulfur pressure range $${\text{p}}_{{\text{S}}_{\text{2}} } = 10^{ - 6} - 10^{ - 2} $$ Pa. Fully developed scales were multilayered consisting of an inner compact layer of equiaxed grains, an intermediate layer of equiaxed and columnar grains exhibiting a small degree of porosity, and an outer porous layer of distinct plates and needles. The grains of the inner and intermediate layers contained quarternary sulfide phases. The following phases were identified: spinels (CrFe)Al2S4 and (FeAl)Cr2S4, hexagonal (FeCr)Al2S4, (CrAlFe)2S3, and (CrAlFe)5S6. The plates and needles were composed of hexagonal (FeCr)Al2S4 and (CrAlFe)2S3 at $${\text{p}}_{{\text{S}}_{\text{2}} } \geqslant 10^{ - 6} $$ and 10−5 Pa from which pyrrhotite, FeS, grew at $${\text{p}}_{{\text{S}}_{\text{2}} } \geqslant 10^{ - 4} $$ .
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    Dependence of reaction rate of 5,5′-dithiobis-(2-nitrobenzoic acid) to free sulfhydryl groups of bovine serum albumin and ovalbumin on the protein conformations (1992)
    Springer
    The protein journal 11 (1992), S. 187-192 
    Details
    ISSN: 1573-4943
    Keywords: 5,5′-Dithiobis(2-nitrobenzoic acid) ; bovine serum albumin ; ovalbumin ; kinetics ; protein conformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of protein conformations on the reaction rate of Ellman's reagent, 5,5′-dithiobis (2-nitrobenzoic acid) (DTNB) with sulfhydryl (SH) groups of proteins was examined. The stopped-flow method was applied to follow the reaction of DTNB with SH group of two proteins, bovine serum albumin (BSA) and ovalbumin (OVA), at various concentrations of guanidine hydrochloride and urea. The rates for both the proteins were faster in guanidine than in urea. The rate sharply depended on the protein conformations, which were monitored by changes of helix contents on the basis of the circular dichroism measurements. The reaction rate of DTNB with SH groups of BSA was maximal around 2 M guanidine and 5 M urea. On the other hand, the reaction rate of DTNB with OVA was maximal at 3.5 M guanidine, while it gradually increased with an increase in the urea concentration. The amount of reactive SH group participating in the reaction with DTNB was also estimated by the absorbance change at 412 nm. The magnitudes of absorbance change for the reaction with free SH groups of OVA at low concentrations of the denaturants were appreciably smaller than those for BSA with one free SH group. Most of the four SH groups of OVA might react with DTNB above 5 M guanidine, although only a part of them did even at 9 M urea.
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    Purification and characterization of diaphorases from someDrosophila species (1992)
    Springer
    Biochemical genetics 30 (1992), S. 305-315 
    Details
    ISSN: 1573-4927
    Keywords: Drosophila ; diaphorase ; purification ; kinetics ; immunochemical characteristics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Diaphorase-1 and diaphorase-2 were isolated from twoDrosophila species,D. virilis andD. melanogaster, and purified by gel filtration, affinity chromatography, immunoaffinity chromatography, and ion-exchange chromatography. The molecular weights of both enzymes were the same in each species. The molecular weight of diaphorase-1 was the same under both denaturating and nondenaturating conditions, close to 60,000, indicating a monomeric structure. Sodium dodecyl sulfate (SDS) electrophoresis of the purified diaphorase-2 revealed the presence of a single protein band of 55,000 Da, while the molecular weight of the native enzyme was found to be 67,000. The two diaphorases were further characterized by their pH optima, isoelectric points, and kinetic parameters, and antibodies were raised in rabbits against the purified enzymes fromD. virilis. The antibodies showed no cross-reactions but recognized the corresponding diaphorases inD. melanogaster andD. novamexicana as well asD. virilis. The data obtained confirmed the hypothesis of an independent genetic control of diaphorase-1 and diaphorase-2 inDrosophila.
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  • 47
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    Purification and characterization of diaphorases from someDrosophila species (1992)
    Springer
    Biochemical genetics 30 (1992), S. 305-315 
    Details
    ISSN: 1573-4927
    Keywords: Drosophila ; diaphorase ; purification ; kinetics ; immunochemical characteristics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Diaphorase-1 and diaphorase-2 were isolated from twoDrosophila species,D. virilis andD. melanogaster, and purified by gel filtration, affinity chromatography, immunoaffinity chromatography, and ion-exchange chromatography. The molecular weights of both enzymes were the same in each species. The molecular weight of diaphorase-1 was the same under both denaturating and nondenaturating conditions, close to 60,000, indicating a monomeric structure. Sodium dodecyl sulfate (SDS) electrophoresis of the purified diaphorase-2 revealed the presence of a single protein band of 55,000 Da, while the molecular weight of the native enzyme was found to be 67,000. The two diaphorases were further characterized by their pH optima, isoelectric points, and kinetic parameters, and antibodies were raised in rabbits against the purified enzymes fromD. virilis. The antibodies showed no cross-reactions but recognized the corresponding diaphorases inD. melanogaster andD. novamexicana as well asD. virilis. The data obtained confirmed the hypothesis of an independent genetic control of diaphorase-1 and diaphorase-2 inDrosophila.
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    Relative kinetics of the homolytic addition of 2-phenyl-1,3-dioxolane to unsaturated compounds (1992)
    Springer
    Russian chemical bulletin 41 (1992), S. 1289-1292 
    Details
    ISSN: 1573-9171
    Keywords: radicals ; addition ; dioxolane ; polar effect ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The CH2 = CHX olefins form a series relative to their reactivity in reactions with 2-phenyl-1,3-dioxolan-2-yl radicals, which qualitatively correlates with the electron-withdrawing capacity of substituent X: CN ≈ CO2Me 〉〉 SiMe3 ≈ C4H9. This behavior indicates that the dioxolanyl radical is nucleophilic.
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    An EPR and molecular mechanics study of radical adducts of phosphonyl radicals with 2-hydroperfluoro-4-methyl-and 4,4-dimethyl-2-pentene (1992)
    Springer
    Russian chemical bulletin 41 (1992), S. 2008-2011 
    Details
    ISSN: 1573-9171
    Keywords: EPR ; radical ; fluorine ; conformation ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract EPR spectra of radical adducts of phosphonyl radicals with 2-hydroperfluoro-4-methyl- and 4,4-dimethyl-2-pentene have been studied. The molecular mechanics method has been used to determine the preferred conformation of the (CF3)2CF-CF-HCF3P(O)(OMe)2 radical. The eclipsed conformation of the C–P bond and 2p z -orbital of an unpaired electron is stabilized due to steric factor and hyperconjugation.
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    Protonation of reagents and acid-base catalysis in acylation (1992)
    Springer
    Russian chemical bulletin 41 (1992), S. 822-828 
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    ISSN: 1573-9171
    Keywords: catalysis ; kinetics ; protonation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetic characteristics of the model reaction of electron transfer and the reaction of acylation of aromatic amines by aromatic acid anhydrides were investigated as a function of the concentration of acid catalyst and a correlation was established between the type of this function and the characteristics of protonation of the amines. The rate constants of the catalytic and noncatalytic flows of the forward and reverse reactions in the phthalic anhydride—p-toluidine system were determined as a function of the molarity and proton-acceptor properties of the solvent. The mechanism of acid-base catalysis was examined as a sequence of proton and electron transfer processes.
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    Dealkylation ofpara-nitrophenyldimethyl thiophosphate in micellar and liquid-crystalline media of then-decylammonium chloride-n-decylamine-water system (1992)
    Springer
    Russian chemical bulletin 41 (1992), S. 817-821 
    Details
    ISSN: 1573-9171
    Keywords: lyotropic liquid crystals ; mixed micelles ; SF ; decylamine ; decylammonium chloride ; p-nitrophenyldimethyl thiophosphate ; dealkylation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of decomposition of p-nitrophenyldimethyl thiophosphate (1) were investigated spectrophotometrically in the n-decylammonium chloride-n-decylamine-water system (DAC-DA-H2O), in which micellar or lamellar liquid-crystalline phases are formed as a function of the concentration of components. It was shown that1 is dealkylated in both phases. An increase in the surface charge density of associates decreases the rate of dealkylation. The activation energy in the lamellar phase is significantly higher than in the micellar phase.
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    Activation of the Ti(OC4H9)4-Al(C2H5)3 catalytic system in the selective dimerization of ethylene to 1-butene by the grignard reagent (1992)
    Springer
    Russian chemical bulletin 41 (1992), S. 1781-1786 
    Details
    ISSN: 1573-9171
    Keywords: dimerization ; kinetics ; ethylene ; organomagnesium compound ; 1-butene ; selectivity ; catalytic activity ; polarography ; reduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of an organomagnesium compound on the dimerization of ethylene to 1-butene was studied. The organomagnesium compound increases the catalytic activity of the Ti(OC4H9)4-Al(C2H5)3 system by 5–10 times. A high degree of selectivity (up to 99%) with respect to 1-butene was obtained. This makes it possible to eliminate a series of technological difficulties involved in the industrial production of 1-butene. The kinetics of the reduction of Ti(OC4H9)4 by butylmagnesium chloride were studied by ESR and polarography.
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    Kinetics of rearrangement of 2,4-dichlorophenyl-(1H-1,2,4-triazol-1-ylmethyl)ketone enol acetate (1992)
    Springer
    Russian chemical bulletin 41 (1992), S. 1787-1789 
    Details
    ISSN: 1573-9171
    Keywords: enol acetate ; rearrangement ; kinetics ; 2,4-dichlorophenyl(1H-1,2,4-triazol-1-ylmethyl)ketone ; 2,4-dichlorophenyl(5-acetyl-1H-1,2,4-triazol-1-ylmethyl)ketone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of rearrangement of 2,4-dichlorophenyl(1H-1,2,4-triazol-1-ylmethyl)ketone enol acetate into 2,4-dichlorophenyl(5-acetyl-1H-1,2,4-triazol-l-ylmethyl)ketone were investigated by1H NMR spectroscopy. It was shown that this rearrangement is a first-order reaction. The rate constant was measured in the 129–156°C range and the activation parameters of the reaction were determined. A hypothesis concerning the intramolecular character of the observed rearrangement was drawn based on the kinetic data.
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    Voltammetric study of reactions of triphenylphosphite ozonide (1992)
    Springer
    Russian chemical bulletin 41 (1992), S. 65-67 
    Details
    ISSN: 1573-9171
    Keywords: kinetics ; decomposition ; ozonide ; triphenylphosphite ; ozonation ; voltammetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The electrochemical characteristics of reduction of triphenylphosphite ozonide at a stationary platinum electrode were determined in acetonitrile at between −30 and −11°C. The feasibility of employing voltammetric methods to investigate the reactions of phosphite ozonides was demonstrated in a model study of the kinetics of the thermal decomposition of (C6H5O)3PO3 and its reaction with triphenylphosphite.
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    Formation of mercury clusters during pulsed radiolysis of aqueous Hg 2 2+ solutions (1992)
    Springer
    Russian chemical bulletin 41 (1992), S. 1-4 
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    ISSN: 1573-9171
    Keywords: radiolysis ; clusters ; kinetics ; mercury ; aqueous solution ; optical spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pulsed radiolysis, EPR, and optical spectroscopy were used to investigate the radiation-induced reduction of Hg 2 2+ ions in aqueous solutions. It was shown that the Hg 2 + ions that form as a result of the reduction reaction react rapidly with Hg 2 2+ with formation of Hg 4 3+ . Constants of formation and disappearance of these ions were determined. The process of disappearance of this species results in the formation of more complex clusters containing six or more mercury atoms. Further complication of the clusters affords colloidal metal particles.
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    Rate constants for addition of phenoxyl radicals to the vinyl monomer double bond (1992)
    Springer
    Russian chemical bulletin 41 (1992), S. 2147-2151 
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    ISSN: 1573-9171
    Keywords: vinyl monomers ; radical oxidation ; inhibitors ; phenols ; reactivity ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Rate constants were measured for the addition of the 2,4,6-tri(tert-butyl)phenoxyl radical (logk 10, [liter/(mole · sec)]) to the double bond of styrene (9.73 − 4621/T), methyl methacrylate (10.1 − 4972.7/T) and butylacrylate (7.68 − 4313.9/T); and for addition of the 2,4,6-tribromophenoxyl radical to styrene (k 10=0.5;T=323 K). A simulation based on these constants for the inhibited oxidation of styrene under conditions similar to those of monomer storage demonstrated the need to take account of this reaction when analyzing kinetic schemes describing the inhibited oxidation process.
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    Radical telomerization of 3,3,3-trifluoropropene with 2-methyl-1,3-dioxolane (1992)
    Springer
    Russian chemical bulletin 41 (1992), S. 2197-2200 
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    ISSN: 1573-9171
    Keywords: radicals ; addition ; dioxolane ; telomers ; telomerization ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The telomerization of 3,3,3-trifluoropropene with 2-methyl-1,3-dioxolane gives predominantly cyclic telomers as shown by13C NMR and gas chromatography-mass spectrometry. This reaction is accompanied by the rearrangement of transient free radical intermediates via 1,5-H-migration.
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    Kinetics of the transesterification of para-nitrophenyl esters of phosphorus acids in water and aqueous hexamethylphosphorotriamide (1992)
    Springer
    Russian chemical bulletin 41 (1992), S. 363-366 
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    ISSN: 1573-9171
    Keywords: kinetics ; transesterification ; acid esters ; sodium phenolate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The rate constants for the substitution of the para-nitrophenoxide ion by the phenoxide and hydroxide ions in phosphates and phosphonates are enhanced upon the addition of hexamethylphosphorotriamide (HMPTA) to water. The lack of alkaline hydrolysis of the esters in 90% aqueous HMPTA containing PhONa is a consequence of the formation of the PhOH... OH complex, which is nonreactive.
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    Mechanism of hydrolysis of azalactones catalyzed by a complex of Cu(II) with (S)-2-[(N-benzylpropyl)amino]benzaldoxime (1992)
    Springer
    Russian chemical bulletin 41 (1992), S. 422-429 
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    ISSN: 1573-9171
    Keywords: azalactones ; hydrolysis ; kinetics ; mechanism ; catalysis ; metal complexes ; enantioselectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hydrolysis of 2-methyl-4-benzyl-5(4H)oxazolone (MBA) in a mixture of water and MeCN has been studied — both the spontaneous reaction and that catalyzed by a complex of Cu(II) with (S)-2-[(N-benzylpropyl)amino]benzaldoxime (1). It has been shown that the complex 1 is an effective catalyst for the hydrolysis of MBA (chymotrypsin does not catalyze MBA hydrolysis). The mechanism of MBA hydrolysis catalyzed by this complex includes the formation of a mixed catalyst—substrate complex in which the MBA is coordinated with the metal ion through the N 3 atom. It is suggested that the oxygen atom of the ionized oxime group in such a complex attacks the imine C 2 atom of the MBA intramolecularly; this is the rate-determining stage. The change in the order of hydrolysis with respect to the catalyst from 1 to 1/2 when the concentration of 1 is increased indicates that the complex catalyst exists in aqueous solution in two forms, dimeric and monomeric, which are in equilibrium, and only the monomeric form of the complex is responsible for the catalysis. With an excess of the substrate we observe inhibition of the MBA hydrolysis — possibly an indirect indication of participation in the transition state by a water molecule coordinated in an apical position of the complex, which is displaced by excess substrate.
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    Salbutamol disposition and dynamics in conscious rabbits: Influence of the route of administration and of the dose (1992)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 20 (1992), S. 461-476 
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    ISSN: 1573-8744
    Keywords: salbutamol ; kinetics ; dynamics ; first-pass effect ; route of administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This study assessed the influence of dose and route of administration on salbutamol kinetics and hypokaliemic effect. Salbutamol plasma kinetics were studied in a first group of 6 rabbits who received 60, 800, and 60 μg/kg by the intravenous (iv), oral (po), and intratracheal (it) routes, respectively, at 1-week intervals. A second group of 6 rabbits received 120, 2400, and 120 μg/kg of salbutamol by the same three routes. Multiple blood samples were withdrawn to assay salbutamol and potassium. Following iv salbutamol (60 μg/kg), total plasma clearance was 82±5 ml/min per kg, apparent volume of distribution was 5.0±0.5 l/kg, and terminal half- life was 41±2 min. Similar values were estimated when 120 μg/kg of salbutamol was administered iv or was given po or it. The bioavailability of po and it salbutamol was approximately 1 and 20%, respectively. For the first group, the maximal decrease in plasma potassium elicited by salbutamol was 0.80±0.19, 0.48±0.22, and 0.78±0.46 mmol/l, and for the second group, maximal decrement was 1.31±0.37, 0.70±0.24, and 0.84±0.17 mmol/l for the iv, po, and it routes, respectively. Compared to salbutamol peak plasma concentrations, maximal decrease in plasma potassium appeared between 60 and 108 min later for the iv route, 90 and 25 min later for po and it routes, and for this reason, the hypokaliemic effect was not associated to salbutamol plasma concentrations. The hypokaliemic effect was dependent upon the route, e.g., po〉it〉iv. It is concluded that (i) salbutamol plasma kinetics are first-order independently of the route of administration, and (ii) salbutamol hypokaliemic effect is modulated by the dose and the route of administration.
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    The effect of aluminium on phosphate uptake by three isolated ectomycorrhizal fungi (1992)
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    Plant and soil 140 (1992), S. 167-174 
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    ISSN: 1573-5036
    Keywords: aluminium ; ectomycorrhizal fungi ; kinetics ; Laccaria bicolor ; Lactarius hepaticus ; Lactarius rufus ; liquid culture ; P uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Three ectomycorrhizal fungi, Laccaria bicolor, Lactarius hepaticus and Lactarius rufus, were grown in liquid medium for 2 weeks and used in short-term phosphate (P) uptake studies. At phosphate concentrations ranging from 1 to 100 μM the fungi exhibited a single affinity phase. The kinetic parameters for P uptake differed between species with Km varying from 1.5 to 13.1 μM. Vmax also depended on the buffer that was applied. P uptake by the fungi was severely reduced by aluminium (Al). This could be ascribed mainly to the complexing of phosphate by Al3+. Correcting for this decrease in phosphate concentration, the uptake by both Lactarius hepaticus and Laccaria bicolor was only slightly inhibited by Al, while P uptake by Lactarius rufus was even stimulated. The latter may be attributed to a reduction in surface potential caused by the trivalent Al cation, which in turn increases the concentration of the negatively charged phosphate ion in the near-membrane region.
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    Nitrogen and phosphorus cycling in relation to stand age of Ecucalyptus regnans F. Muell (1992)
    Springer
    Plant and soil 142 (1992), S. 157-166 
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    ISSN: 1573-5036
    Keywords: Acacia ; Eucalyptus regnans ; decomposition ; litterfall ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The N and P contents of the litter layer and the return of these nutrients in litterfall were measured in seven stands of Mountain Ash (Eucalyptus regnans) ranging in age from 5 years to about 250 years. Both annual litterfall and nutrient return were correlated with stand basal area and were high compared with other productive eucalypt forests. In contrast, the fall of dead eucalypt leaves was constant with stand age, demonstrating that sites are fully occupied at an early age. Similarly, amounts of N and P in total leaf fall (overstorey plus understorey) were constant with stand age, except for low amounts in the stand aged 40 years where Acacia spp., important fixers of atmospheric N, were not prevalent. The decomposition constant (k) of organic matter in the litter layer decreased with stand age, from 0.31 year-1 at age 5 years to 0.23 year-1 at age 250 years. These constants also applied to N and P, indicating a tight coupling between organic matter decomposition and release of these nutrients from litter. The litter layer released about 30 kg ha-1 of N at age 5 years, and about 70 kg ha-1 at age 80 years. These results are discussed in relation to growth of Mountain Ash following fire, and the subsequent retention and accumulation of N during stand development.
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    Soil phosphorus status, pH and the manganese nutrition of wheat (1992)
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    Plant and soil 145 (1992), S. 45-50 
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    ISSN: 1573-5036
    Keywords: acidity ; manganese ; pH ; phosphorus ; soil solution wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A pot experiment was carried out in order to test the hypothesis that manganese nutrition of wheat was dependent on the phosphorus status of soil as well as on its pH and manganese status. An arable mineral soil whose lime and phosphorus status had been massively adjusted more than 18 years previously was compared with identical soil not so adjusted. Wheat plants were grown to maturity in these soils. Analyses were carried out on both soil and plant samples at intervals. Data for soil pH, soil solution concentrations of manganese and phosphorus, plant dry weight and tissue concentrations of manganese and phosphorus are presented. Concentrations of manganese were depressed in leaf tissue of plants from limed soils and also in high phosphorus soils. The depressed values for limed treatments were explained in terms of depressed soil solution manganese concentrations resulting from elevated pH. The results for high phosphorus soils could not be related to soil solution composition. It was suggested that high soil phosphorus resulted in elevated plant phosphorus which interfered in the uptake and/or translocation of manganese.
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    A review of phosphorus efficiency in wheat (1992)
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    Plant and soil 146 (1992), S. 163-168 
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    ISSN: 1573-5036
    Keywords: genetic variability ; NIR ; ploidy ; phosphorus ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract More efficient utilization of phosphorus by wheat plants is needed to extend the useful life of the phosphate reserves in the world, to reduce the cost of producing crops, and to improve the value of the grain and the straw produced. In this paper definitions of efficient use of phosphorus by wheat are reviewed, genotypic variation in phosphorus efficiency is reported, some consequences of breeding for greater efficiency are discussed, and ways to select more efficient genotypes are suggested.
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    Influence of plant nutrient concentration on growth rate: Use of a nutrient interruption technique to determine critical concentrations of N, P and K in young plants (1992)
    Springer
    Plant and soil 142 (1992), S. 221-233 
    Details
    ISSN: 1573-5036
    Keywords: critical concentration ; deficiency ; diagnosis ; growth rate ; lettuce ; luxury consumption ; nitrogen ; nitrate ; nutrient requirement ; petiole sap ; phosphorus ; phosphate ; potassium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A method is described for determining the way in which growth rate varies with plant nutrient concentration using a simple nutrient interruption technique incorporating only 2 treatments. The method involves measuring the changes in growth and nutrient composition of otherwise well-nourished plants after the supply of one particular nutrient has been withheld. Critical concentrations are estimated from the relationship between the growth rate (expressed as a fraction of that for control plants of the same size which remained well-nourished throughout) and the concentration of the growth-limiting nutrient in the plants as deficiency developed. Trials of the method using young lettuce plants showed that shoot growth rate was directly proportional to total N (nitrate plus organic N) concentration, and linearly or near-linearly related to K and P concentration over a wide range; the corresponding relationship for nitrate was strongly curvi-linear. Critical concentrations (corresponding to a 10% reduction in growth rate) determined from these results were similar to critical values calculated from models derived from field data, but were generally higher than published estimates of critical concentration (based on reductions in shoot weight) for plants of a similar size. Reasons for these discrepancies are discussed. Nitrate, phosphate or potassium concentrations in sap from individual leaf petioles were highly sensitive to changes in shoot growth rate as deficiency developed, with the slope of the relationships varying with leaf position, due to differences both in their initial concentration and in the rates at which they were utilized in individual leaves. Each nutrient was always depleted more quickly in younger leaves than in older ones, providing earlier evidence of deficiency for diagnostic purposes. Although the plants were capable of accumulating nitrate, phosphate and potassium well in excess of that needed for optimum dry matter production during periods of adequate supply, the rate of mobilization of these reserves was insufficient to prevent reductions in growth rate as the plants became deficient. This brings into question the validity of the conventional concept that luxury consumption provides a store of nutrients which are freely available for use in times of shortage. The implications of these results for the use of plant analysis for assessing plant nutrient status are discussed.
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    Inability to solubilize phosphate in limestone soils—key factor controlling calcifuge habit of plants (1992)
    Springer
    Plant and soil 145 (1992), S. 65-70 
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    ISSN: 1573-5036
    Keywords: calcifuge plants ; phosphorus ; deficient absorption ; Deschampsia flexuosa ; Jasione montana ; Rumex acetosella ; Silene rupestris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Germination, seedling establishment and growth of calcifuge plants in Swedish limestone soils of Archean and Ordovician age were studied. As previously demonstrated for Viscaria vulgaris, establishment of Rumex acetosella and Silene rupestris did not succeed unless CaHPO4 (at the rate of 10 mmol dm-3 of soil) was supplied. Growth of Deschampsia flexuosa was enhanced by phosphate addition, whereas establishment success of Jasione montana was poor, regardless of phosphate treatment. Establishment and growth in an acidic gneiss soil, used as a reference for the species studied, was good. Total, total inorganic, exchangeable, and soil solution P were considered in all soils and treatments. It is proposed that the calcifuge behaviour of plants is quite often caused by inability to solubilize the native phosphate of limestone soils.
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    Can maize cultivars with low mineral nutrient concentrations in the grains help to reduce the need for fertilizers in third world countries? (1992)
    Springer
    Plant and soil 146 (1992), S. 227-231 
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    ISSN: 1573-5036
    Keywords: cultivars ; grains ; maize ; nitrogen ; phosphorus ; potassium ; tropical climate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An earlier study revealed considerable genotypic variation in grain N, P and K concentrations (GNC, GPC and GKC, respectively) in tropical maize. The expression of varietal differences in GNC, GPC and GKC, however, may depend on environmental conditions such as the N status of the soil. Two tropical maize hybrids (Suwan 2301 and CP 1) with comparable yielding capacity, but contrasting GNCs, GPCs and GKCs, were therefore grown at four levels of N in a field experiment at Farm Suwan (Thailand, latitude 14.5°N). Suwan 2301 exhibited a higher GNC than did CP 1 at all rates of N, but large differences in GPC and GKC were found only at high N fertilization. This was obviously due to individual grain yield responses of the cultivars to increasing rates of N fertilizer, demonstrating that grain nutrient concentrations are, at least in part, functions of the amount of grain carbohydrates which dilute a genetically and environmentally fixed amount of grain P and K. As compared to Suwan 2301, CP 1 accumulated less N, P and K in the grains at almost all levels of N fertilization, confirming our hypothesis that the cultivation of maize genotypes with low grain mineral nutrient concentrations may help third-world cash-crop farmers to reduce the need for scarce and costly mineral fertilizers. This finding has to be verified at reduced availability of soil −P, −K, and water.
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    Effects of phytoplankton on the elemental composition (C, N, P) of suspended particulate material in the lower river Rhine (1992)
    Springer
    Hydrobiologia 235-236 (1992), S. 479-489 
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    ISSN: 1573-5117
    Keywords: River Rhine ; phytoplankton ; suspended material ; carbon ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The spatial and temporal distribution of element concentrations were monitored together with chlorophyll a as an indicator of algal density to assess the effect of phytoplankton on the elemental composition (C, N, P) of suspended materials in the lower Rhine. The high concentrations of particulate C, N and P in the river were found to decrease in the delta and to increase again in the estuarine turbidity zone. Phytoplankton blooms increased the concentrations of particulate C, N, and P significantly in the upstream part of the river. In summer 1989, 15–65% of the particulate C and 20–75% of the particulate N were attributable to phytoplankton. Together with published data these observations indicate that in eutrophic rivers, the input of organic materials from the catchment is strongly modified and supplemented by in situ growth of phytoplankton. During seaward transport the phytoplankton and the particulate elements disappeared from the river water concomitantly with the suspended matter, indicating an increased retention of these elements due to sedimentation. In contrast, soluble ammonia, nitrite and phosphate increased in the tidal reaches of the river because of local input in the harbour and city of Rotterdam and because of mineralization. Therefore the total nutrient load of the Rhine estimated at the German/Dutch border does not reflect the actual input into the sea.
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    Iron:phosphorus ratio in surface sediment as an indicator of phosphate release from aerobic sediments in shallow lakes (1992)
    Springer
    Hydrobiologia 235-236 (1992), S. 731-743 
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    ISSN: 1573-5117
    Keywords: Lakes ; sediments ; iron ; phosphorus ; phosphate release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Analysis of Danish lakes showed that both mean winter and mean summer concentrations of lake water total phosphorus in the trophogenic zone correlated negatively with the total iron to total phosphorus ratio (Fe:P) in surface sediments. No correlation was found between the water total phosphorus concentration and either the sediment phosphorus concentration alone or with sediment calcium concentration. The increase in total phosphorus from winter to summer, which is partly a function of net internal P-loading, was lowest in lakes with high Fe:P ratios in the surface sediment. A study of aerobic sediments from fifteen lakes, selected as representative of Danish lakes with respect to the sediment Fe and phosphorus content, showed that the release of soluble reactive phosphorus was negatively correlated with the surface sediment Fe:P ratio. Analysis of phosphate adsorption properties of surface sediment from 12 lakes revealed that the capability of aerobic sediments to buffer phosphate concentration correlated with the Fe:P ratio while the maximum adsorption capacity correlated with total iron. Thus, the Fe:P ratio may provide a measure of free sorption sites for orthophosphate ions on iron hydroxyoxide surfaces. The results indicate that provided the Fe:P ratio is above 15 (by weight) it may be possible to control internal P-loading by keeping the surface sediment oxidized. Since the Fe:P ratio is easy to measure, it may be a useful tool in the management of shallow lakes.
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    Biogeochemistry of manganese- and iron-rich sediments in Toolik Lake, Alaska (1992)
    Springer
    Hydrobiologia 240 (1992), S. 45-59 
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    ISSN: 1573-5117
    Keywords: arctic lakes ; trace metals ; lake sediments ; manganese ; iron ; phosphorus ; sediment-water flux ; diagenesis ; Toolik Lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The sediments within Toolik Lake in arctic Alaska are characterized by extremely low rates of organic matter sedimentation and unusually high concentrations of iron and manganese. Pore water and solid phase measurements of iron, manganese, trace metals, carbon, nitrogen, phosphorus, and sulfur are consistent with the hypothesis that the reduction of organic matter by iron and manganese is the most important biogeochemical reaction within the sediment. Very low rates of dissolved oxygen consumption by the sediments result in an oxidizing environment at the sediment-water interface. This results in high retention of upwardly-diffusing iron and manganese and the formation of metal-enriched sediment. Phosphate in sediment pore waters is strongly adsorbed by the metal-enriched phases. Consequently, fluxes of phosphorus from the sediments to overlying waters are very small and contribute to the oligotrophic nature of the Toolik Lake aquatic system. Toolik Lake contains an unusual type of lacustrine sediment, and in many ways the sediments are similar to those found in oligotrophic oceanic environments.
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    Sources, concentrations and characteristics of organic matter in softwater lakes and streams of the Swedish forest region (1992)
    Springer
    Hydrobiologia 229 (1992), S. 23-41 
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    ISSN: 1573-5117
    Keywords: TOC ; COD ; humic ; colour ; Secchi ; phosphorus ; carbon ; permanganate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 18 Swedish forest lakes covering a wide range of dystrophy were studied in order to quantify and characterize the organic matter in the water with respect to origin (allochthonous or autochthonous), physical state (particulate or dissolved) and phosphorus content. Samples were collected repeatedly during a two-year period with unusually variable hydrological conditions. Water from three different depths and from tributaries was analysed with standard monitoring methods, including water colour, Secchi disk transparency, total organic carbon (TOC), CODCr, CODMn, total phosphorus and molybdate reactive phosphorus. Interrelationships were used to compare different methods and to assess the concentration and composition of organic matter. It is estimated that in remote softwater lakes of the Swedish forest region, autochthonous carbon is typically 〈 5 g m−3. Most lakes in this region receive significant amounts of humic matter originating from coniferous forest soils or peatland in the catchment area. In most humic lakes with a water colour of ≥ 50 g Pt m−3, more than half of the organic carbon in the surface water is of allochthonous origin, and in polyhumic lakes (〉 200 g Pt m−3) the proportion can exceed 90%. Secchi depth readings were related similarly to organic matter from both sources and provided good estimates of TOC with a single optical measurement. Water colour was used to distinguish allochthonous and autochthonous matter. High concentrations of phosphorus were found in humic waters, most of it being molybdate reactive, and probably associated with humic matter rather than as dissolved free inorganic forms. CODMn yielded only 25–60% of TOC and appears to include mainly truly dissolved substances of low molecular weight.
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    Nutrient loading and drainage channel response in a ricefield system (1992)
    Springer
    Hydrobiologia 230 (1992), S. 193-200 
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    ISSN: 1573-5117
    Keywords: nitrogen ; phosphorus ; ricefield system ; drainage channels ; mediterranean Deltas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen and phosphorus released into the water of a main drainage channel in the Ebro Delta was measured during a period of rice cultivation. An increase in total nitrogen and phosphorus in its different forms in accordance with the increase in cultivated area drained was observed. A significant correlation between the release of nutrients into the water and the nutrient load, for both nitrogen and phosphorus, if we consider the release of nutrients per unit of length of the channel and increased total phosphorus content of the water that flows through it during the period of rice cultivation. Physical and chemical changes in the water as a result of ricefield metabolism may explain the differences observed in nitrogen and phosphorus cycles between Ebro and Rhône Deltas, two mediterranean deltaic systems where a large area with similar drainage system is used for rice cultivation.
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    Changes in water quality in Lake Päijänne following decrease of effluent load from the pulp and paper industry in 1969–1989 (1992)
    Springer
    Hydrobiologia 243-244 (1992), S. 395-403 
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    ISSN: 1573-5117
    Keywords: Lake Päijänne ; pulp mills ; BOD ; phosphorus ; water quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Päijänne, the second largest lake in Finland, has been seriously polluted since the 1960s due to the effluents from pulp and paper mills, notably the Äänekoski sulphate and sulphite pulp mills situated about 50 km north of the lake, and the sulphite pulp mill and paper mills of Jämsänkoski and Kaipola on Central Lake Päijänne. A sulphite lye evaporation and combustion plant installed at the Jämsänkoski sulphite pulp mill in 1969 reduced the organic pollution of Central Päijänne. Lignin concentration decreased and the oxygen balance improved. The sulphite pulp mill was closed in 1981 and replaced by a thermo-mechanical pulp mill. Eutrophication is the main threat to water quality in Central Lake Päijänne at present. A significant improvement in the water quality, especially in oxygen balance, was achieved in the watercourse of Äänekoski and in Northern Päijänne after replacement of the old sulphite and sulphate pulp mills at Äänekoski by a large sulphate pulp mill with a biological purification plant employing the activated sludge method. The BOD7-loading dropped from 46 to 3–4 t d−1, but the nutrient loading has not decreased sufficiently, and the Äänekoski watercourse and Northern Päijänne are still eutrophic.
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    Bioassay for phosphate demand in phytoplankton from acidified lakes: Lake Njupfatet, an example of phosphate deficiency induced by liming (1992)
    Springer
    Hydrobiologia 246 (1992), S. 99-110 
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    ISSN: 1573-5117
    Keywords: acid lakes ; ATP ; in situ enclosures ; liming ; phosphatases ; phosphorus ; phytoplankton community
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A bioassay was developed, involving steady-state ATP level determinations, for estimation of phosphate demand and deficiency in natural phytoplankton communities. The studies were performed on phytoplankton from the moderately acidified Lake Njupfatet in central Sweden before and after liming. Phytoplankton samples from in situ enclosure experiments with low-dose enrichments of nitrate and phosphate and removal of large (〉 100 µm) zooplankton and from the lake water were collected. The phytoplankton were concentrated by through-flow centrifugation and post-cultured in the laboratory with or without the addition of phosphate. A relative increase in the ATP:chlorophyll a ratio after the phosphate treatment as compared to samples without phosphate enrichment was found to be a highly reproducible indicator of phosphate deficiency in the natural phytoplankton population. In contrast, the absolute ATP:chlorophyll a ratio varied substantially between different sampling occasions. No phosphate deficiency was detected in phytoplankton from the acidic lake or from fertilized in situ enclosures. However, phytoplankton from in situ enclosures without added nutrients showed evidence of phosphate limitation after 21 days incubation. Also, the phytoplankton community developed a significant phosphate deficiency the summer after lake liming. The results from the ATP analyses are compared with chemical data of the lake water, phytoplankton community structure and phosphatase activities in the lake before and after liming. The average total biomass of phytoplankton and the average Tot-P measured during May to September decreased with appr. 30% after liming while Tot-N was essentially unaffected and the phosphatase activities increased by 1000–2000%.
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    Regeneration of inorganic phosphorus and nitrogen from decomposition of seston in a freshwater sediment (1992)
    Springer
    Hydrobiologia 228 (1992), S. 71-81 
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    ISSN: 1573-5117
    Keywords: nutrient regeneration ; phosphorus ; nitrogen ; sediment ; lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mineralization of phosphorus and nitrogen from seston was studied in consolidated sediment from the shallow Lake Arreskov (July and November) and in suspensions without sediment (July). In the suspension experiment, phosphorus and nitrogen were mineralized in the same proportions as they occurred in the seston. During the 30 days suspension experiment, 47 and 43% of the particulate phosphorus and nitrogen, respectively, was mineralized with constant rates. Addition of seston to the sediment had an immediate enhancing effect on oxygen uptake, phosphate and ammonia release, whereas nitrate release decreased due to denitrification. The enhanced rates lasted for 2–5 weeks, while the decrease in nitrate release persisted throughout the experiment. The increase in oxygen uptake (equivalent to 21% of the seston carbon) was, however, only observed in the July experiment. The release of phosphorus and nitrogen from seston decomposing on the sediment surface differed from the suspension experiments. Thus, between 91 and 111% of the phosphorus in the seston was released during the experiments. Due to opposite directed effects on ammonium and nitrate release, the resulting net release of nitrogen was relatively low. A comparison of C/N/P ratios in seston, sediment and flux rates indicated that nitrogen was mineralized faster than phosphorus and carbon. Some of this nitrogen was lost through denitrification and therefore not measurable in the flux of inorganic nitrogen ions. This investigation also suggests that decomposition of newly settled organic matter in sediments have indirect effects on sediment-water exchanges (e.g. by changing of redox potentials and stimulation of denitrification) that modifies the release of mineralized phosphate and nitrogen from the sediment.
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    The influence of flushing on nutrient dynamics, composition and densities of algae and transparency in Veluwemeer, The Netherlands (1992)
    Springer
    Hydrobiologia 233 (1992), S. 187-196 
    Details
    ISSN: 1573-5117
    Keywords: eutrophication ; lake restoration ; flushing ; Veluwemeer ; algal species ; transparency ; phosphorus ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Total phosphorus and chlorophyll decreased significantly after reduction of the external phosphorus loading and the start of flushing Veluwemeer with polder water in 1979. Flushing of Veluwemeer has had a large impact on nutrient dynamics. Especially in the first winter, dilution was the main cause of changes in water quality. On a longer term the increase of the inactivation of phosphorus in sediments is important. Oscillatoria agardhii has been brought to the margins of its habitat. Three successive cold winters were an additional causal factor in the disappearance of Oscillatoria agardhii and the dominance of diatoms and green algae from 1985 onwards. Due to higher detritus and inorganic suspended matter concentrations transparency increased less than expected. Since 1985 chlorophyll only contributes for a small percentage to the transparency. In the present situation further improvement of the water quality of Veluwemeer is questionable, as the phosphorus concentration in the lake and the polder water is almost the same. Therefore it is recommanded to shift flushing operations, at least in the winter period, from Veluwemeer towards Wolderwijd.
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    Fixation of phosphorus in lake sediments using iron(III)chloride: experiences, expectations (1992)
    Springer
    Hydrobiologia 233 (1992), S. 211-212 
    Details
    ISSN: 1573-5117
    Keywords: eutrophication ; lake restoration ; phosphorus ; sediments ; internal loading ; chemomanipulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract After a reduction of the external phosphorus loading to a lake, an internal loading from the sediments may delay the improvement of the water quality. The accepted method to combat internal loading is careful dredging of the upper sediment layers (Cooke et al., 1986), but this method is costly and time consuming. Addition of phosphorus binding agents to the sediments might offer an alternative. In the Netherlands the use of aluminum compounds, the most common phosphorus binding agent, for water quality improvement purposes is not favoured. Therefore a sediment treatment with a solution of iron(III)chloride was tested. Iron was chosen because it is considered to be a natural binder of phosphate. 100 g m−2 of Fe3+ were added to the sediments of the shallow (1.75 m average depth) and eutrophic Lake Groot Vogelenzang (The Netherlands) in October and November 1989. The iron(III)chloride solution was diluted 100 times with lake water and mixed with the surface sediments with a water jet. Following the addition the concentrations of total phosphorus (Fig. 1), chlorophyll-a and suspended solids decreased. This improvement of the water quality lasted for three months. After this time the total phosphorus concentration increased again, but remained at a lower level than in spring and summer of 1989. The phosphorus release rate from the sediments as measured from intact sediment cores decreased from 4 to 1.2 mg P m−2 d−1 (n = 5), and the bioavailability of the sediment phosphorus, as measured with bioassays, decreased from 34 to 23% (n = 5) shortly after the treatment. One year after the treatment the release rate was increased to 3 mg P m−2 d−1 (n = 5). Before treatment, the lake was thought to have a residence time of over one year. However, the chloride added to the lake disappeared according to a dilution rate of 0.03 d−1 or a retention time of about 35 days. A high external loading due to rapid flushing with phosphorus-rich water from surrounding lakes possibly prevented a more durable improvement in water quality. Another possibility is that the iron addition has lost its phosphate binding capacity due to reduction or binding with other anions like carbonate or sulphide. Therefore the suitability of the method to reduce internal loading and especially the long term availability of added iron to bind phosphorus needs additional proof. The treatment of the 18 ha area of Lake Groot Vogelenzang took three weeks. The operational costs were about US$ 125000. This is fast and cheap compared to dredging. Application of the technique is limited to those cases where the sediments are not polluted with micro-pollutants and the water depth need not be increased.
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    Phosphorus eutrophication in the SW Frisian lake district 1. Monitoring and assessment of a dynamic mass balance model (1992)
    Springer
    Hydrobiologia 233 (1992), S. 259-270 
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    ISSN: 1573-5117
    Keywords: eutrophication ; lakes ; phosphorus ; chloride ; loading ; dynamic mass balance model ; sensitivity analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In 1984 a frequent monitoring programme was started in the hypertrophic S.W. Frisian lake district, with emphasis on total phosphorus (TP) and chloride (Cl−). The main objectives of the project were: to quantify the phosphorus flows, to gain insight in the process of eutrophication, and to simulate management scenarios. The seasonal variability in the lakes is due mainly to the man-made hydrology: reception of humic-rich polder water in wet periods (winter) and inlet of chloride-rich Usselmeer water in dry periods (summer). The yearly means of TP concentrations in the lakes (Tjeukemeer, Groote Brekken and Slotermeer) ranged from 0.23 to 0.29 mg l−1. However, much higher concentrations (0.9 mg l−1) were found in periods with high inflow of polder water. The simulations with a mass balance showed an acceptable similarity between measured and simulated concentrations of TP as well as of Cl−. Chloride was modelled to verify the accuracy of a hydrodynamic model. A sensitivity analysis of the apparent settling rate in the P model showed that sensitivity was lowest in simulations of Groote Brekken and highest in simulations of Slotermeer, the difference being attributable to the influence of the water residence time. The model was found to be appropriate for simulating management scenarios.
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    A mathematical model of the phosphorus cycle in Lake Loosdrecht and simulation of additional measures (1992)
    Springer
    Hydrobiologia 233 (1992), S. 119-136 
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    ISSN: 1573-5117
    Keywords: model ; simulation ; eutrophication ; phosphorus ; P/C ratio ; lake ecosystem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phosphorus cycle in the ecosystem of the shallow, hypertrophic Loosdrecht lakes (The Netherlands) was simulated by means of the dynamic eutrophication model PCLOOS. The model comprises three algal groups, zooplankton, fish, detritus, zoobenthos, sediment detritus and some inorganic phosphorus fractions. All organic compartments are modelled in two elements, carbon and phosphorus. Within the model system, the phosphorus cycle is considered as completely closed. Carbon and phosphorus are described independently, so that the dynamics of the P/C ratios can be modelled. The model has been partly calibrated by a method based on Bayesian statistics combined with a Range Check procedure. Simulations were carried out for Lake Loosdrecht for the periods before and after the restoration measures in 1984, which reduced the external phosphorus loading to the lake from ca. 2 mgP m−2 d−1 to 1 mgP m−2 d−1. The model outcome was largely comparable withthe measured data. Total phosphorus has slowly decreased from an average 130 µgP l−1 to ca. 80 µgP l−1, but chlorophyll-a (ca. 150 µg 1−1, summer-averaged) and seston concentrations (8–15 mgC 1−1) hardly changed since the restoration measures. About two-thirds of the seston consisted of detritus, while the phytoplankton remained dominated by filamentous cyanobacteria. The P/C ratio of the seston decreased from ca. 1.0% to 0.7%, while the P/C ratios of zooplankton, zoobenthos and fish have remained constant and are much higher. The system showed a delayed response to the decreased phosphorus loading until a new equilibrium was reached in ca. five years. Major reasons for the observed resilience of the lake in responding to the load reduction are the high phosphorus assimilation efficiency of the cyanobacteria and the high internal recycling of phosphorus. A further reduction of nutrient loading, perhaps in combination with additional measures like biomanipulation, will be the most fruitful additional restoration measure.
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    Coupling between benthic biomass of Microcystis and phosphorus release from the sediments of a highly eutrophic lake (1992)
    Springer
    Hydrobiologia 235-236 (1992), S. 375-385 
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    ISSN: 1573-5117
    Keywords: Microcystis ; microbial activity ; sediment ; phosphorus ; internal loading
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Variations in microbial biomass and activity in the sediments of hypereutrophic Lake Vallentunasjön were followed during a period of 5 years. The data were compared to the calculated release of phosphorus from the sediments during the same period. A strong co-variation was found between biomass of Microcystis, heterotrophic bacterial activity in the sediments and internal phosphorus loading. These parameters exhibited mainly a declining trend during the investigation period. A pronounced stability of the sediment chemistry, including the fractional composition of the sediment phosphorus, during the studied period indicates that microbial activity affected the phosphorus release from the sediments. Calculations of the percentage of sediment bacteria that was associated to the mucilage of Microcystis colonies imply, together with the specific bacterial production, that Microcystis in the sediment stimulates bacterial production. In the highly phosphorus-saturated sediments of Lake Vallentunasjön this would ultimately lead to an increased release of phosphorus from the sediment. Lake Vallentunasjön does not follow the common pattern of recovery after reduction of external phosphorus loading. The large biomasses and long survival of Microcystis in the sediment are probably important reasons for the delayed recovery of the lake.
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    The turnover of river-transported iron, phosphorus and organic carbon in the Öre estuary, northern Sweden (1992)
    Springer
    Hydrobiologia 235-236 (1992), S. 585-596 
    Details
    ISSN: 1573-5117
    Keywords: estuary ; iron ; phosphorus ; organic carbon ; aggregation ; sedimentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The turnover of iron, phosphorus and organic carbon was followed in the Öre Estuary, northern Sweden, during the spring flood periods of 1989 and 1990. River-supplied material rapidly sediments out of the water column and is primary deposited within the estuary. The removal of iron and phosphorus is complete, with the calculated sedimentation exceeding the total amounts of particulate and dissolved iron and phosphorus supplied by the river. Aggregation of dissolved or colloidal iron-phosphate complexes due to increasing salinity and pH in combination with adsorption on rapidly sedimentating inorganic particles is suggested to explain this estuarine filter effect. Organic carbon is only affected by aggregation and sedimentation to a minor extent.
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    Phosphorus transformations in the epilimnia of small humic forest lakes (1992)
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    Hydrobiologia 243-244 (1992), S. 105-111 
    Details
    ISSN: 1573-5117
    Keywords: phosphorus ; transformations ; humic forest lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Research on epilimnetic phosphorus transformations in lakes had led to the establishment of a generalised picture which is promoted in reviews and textbooks. However, it would be wrong to believe that this established view can be applied to all lakes. Certainly the transformations of phosphorus in the summer epilimnia of small, coloured, humic forest lakes in southern Finland show features which deviate markedly from the generally accepted paradigm. (1) The plankton appears to be limited simultaneously by P and N rather than being strongly P limited. (2) Particulate P is typically a rather small fraction of the total P. (3) Molybdate reactive P may be a large part of the total P, although much of this MRP is not free orthophosphate, especially in highly humic lakes. (4) Turnover times for PO4-P are normally long (50–1000 minutes); turnover times appear to be longer in highly humic lakes. (5) Added 32 PO4 passes rapidly to macrozooplankton, apparently with rapid turnover of zooplankton phosphorus. (6) Sedimentation of phosphorus from the typically shallow epilimnion appears high, but may be partially compensated by biological retrieval of phosphorus from the phosphorus-rich hypolimnion.
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    Phytoplankton and zooplankton community structure after nutrient additions to the oligotrophic Lake Hecklan, Sweden (1992)
    Springer
    Hydrobiologia 243-244 (1992), S. 147-155 
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    ISSN: 1573-5117
    Keywords: fertilization ; phosphorus ; nitrogen ; phytoplankton ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Hecklan, in central Sweden, was fertilized with phosphorus and nitrogen during thermal stratification (late May-early Oct) 1984–1987. The nutrient additions were relatively small and raised the total phosphorus concentrations from 6 to 10 µg l−1. The working hypothesis was that this moderate increase in the phosphorus concentration could increase the phytoplankton biomass without adverse changes in the planktonic community structure. The fertilization increased the phytoplankton biomass from 0.1 to a maximum of 2 mm3 l−1. Chrysophyceae and Cryptophyceae dominated throughout the experimental period. Thus, the phytoplankton composition remained typical for a Swedish forest lake and provided a potential for increased zooplankton growth. An increased growth of zooplankton was indicated by increased biomass of Cladocera and Copepoda in 1984 and 1985, and by increased fecundity of herbivorous zooplankton.
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    Mass balance models for elongated lakes (1992)
    Springer
    Hydrobiologia 243-244 (1992), S. 341-349 
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    ISSN: 1573-5117
    Keywords: mass balance ; modelling ; phosphorus ; sedimentation ; CSTR ; PFR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mass balance models for elongated lakes have been developed. In these models particular attention is paid to the hydraulic description of the lake and to the description of net sedimentation. The hydraulic description is a linear combination of CSTR and PFR, with a coefficient regulating the degree of mixing. The PFR description was modified so that also additional input along the lake can be considered. Net sedimentation is described either as a first order or a second order reaction. Both voluminal and areal sedimentation is possible in the models. The models were tested against phosphorus balance data for two Finnish lakes. Lake Haukivesi and Lake Päijänne. In both lakes the PFR model with additional input together with second order net sedimentation gave the best fit to observations. The values of the sedimentation coefficients are not universal but vary from lake to lake. They are also dependent on the hydraulic description used in the model. There is a critical point for the monitoring of the lake at which measurements give the same sedimentation coefficient regardless of the hydraulic description.
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    Nutrient dynamics in the floodplain ponds of the Paraná River (Argentina) dominated by the water hyacinth Eichhornia crassipes. (1992)
    Springer
    Biogeochemistry 17 (1992), S. 85-121 
    Details
    ISSN: 1573-515X
    Keywords: nitrogen fixation ; phosphorus ; internal loading ; water hyacinth ; floodplain ; Paraná ; flood-pulse hypothesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Some aspects of nutrient status and dynamics prevailing during low and high water conditions in the fringing floodplain ponds of the Paraná River dominated by the floating macrophyte Eichhornia crassipes are described. During summertime low water conditions, low DIN:DRP ratios (0.16–1.0) and low DIN (0.5–4.8 μmol.liter−1) in the root-zone of the floating meadows suggest that macrophyte growth is limited by nitrogen. DRP concentrations appear to be controlled more by abiotic sorption-dissolution than by biological reactions. Preflood nutrient fluxes from the sediments, as estimated from porewater profiles, show that a minimum of 1.19 and 0.38 mmol.m−2.d−1 of DIN and DRP were regenerated from the sediments, respectively. Heterotrophic N2 fixation is primarily associated with decaying litter (0.4 to 3.2 μmolN2.g−1.d−1). Nutrient recycling from sediments and meadow-litter, and heterotrophic N2 fixation (1.4 mmolN.m−2.d−1) appear sufficient to sustain high floating macrophyte productivity for long periods of time, without invoking large inputs from the river. The high water and early isolation periods are characterized by a very dynamic behavior of DIN, reflecting marked imbalances between N supply and demand by the biota. After hydrologic isolation of the ponds, DIN rapidly decreases to undetectable levels and stays low for the following 3 weeks, presumably as a result of high demand by phytoplankton and sediment bacteria. DIN increases again to high values 3–8 weeks after the flood, following the re-establishment of NH4 + fluxes from the sediments. Compared to DIN, DRP concentrations remain relatively high and change little during and after the flood. Because of their small amplitude and short duration, floods do not appear to stimulate floating macrophyte production in the Paraná.
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    Effects of nitrogen: phosphorus supply ratios on nitrogen fixation in agricultural and pastoral ecosystems (1992)
    Springer
    Biogeochemistry 18 (1992), S. 19-35 
    Details
    ISSN: 1573-515X
    Keywords: Dinitrogen fixation ; nitrogen ; phosphorus ; competition ; legumes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract An analysis of data compiled from the literature confirms a strong inverse relationship between annual rates of nitrogen fixation and the soil nitrogen content in agricultural and pastoral ecosystems. However, this inverse relationship is strongly modified by the rate of application of phosphorus fertilizer, which strongly influences the activities of both symbiotic and non-symbiotic nitrogen fixing organisms. In the case of symbiotic legumes, the response of N-fixation to N and P is in part a result of changes in legume dominance within the plant community. These results, as well as supporting data presented from a review of experiments on nitrogen fixation in a variety of other terrestrial and aquatic ecosystems, provide important support for the hypothesis that phosphorus availability is a key regulator of nitrogen biogeochemistry.
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    Soil nutrient dynamics in response to irrigation of a Panamanian tropical moist forest (1992)
    Springer
    Biogeochemistry 19 (1992), S. 1-25 
    Details
    ISSN: 1573-515X
    Keywords: nitrogen ; phosphorus ; soil fertility ; tropical forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We measured concentrations of soil nutrients (0–15 and 30–35 cm depths) before and after the dry season in control and dry-season irrigated plots of mature tropical moist forest on Barro Colorado Island (BCI) in central Panama to determine how soil moisture affects availability of plant nutrients. Dry-season irrigation (January through April in 1986, 1987, and 1988) enhanced gravimetric soil water contents to wet-season levels (ca. 400 g kg−1 but did not cause leaching beyond 0.8 m depth in the soil. Irrigation increased concentrations of exchangeable base cations (Ca2+, Mg2+, K+, Na+), but it had little effect on concentrations of inorganic N (NH4 +C, NO3 − and S (SO4 2−). These BCI soils had particularly low concentrations of extractable P especially at the end of the dry season in April, and concentrations increased in response to irrigation and the onset of the rainy season. We also measured the response of soil processes (nitrification and S mineralization) to irrigation and found that they responded positively to increased soil moisture in laboratory incubations, but irrigation had little effect on rates in the field. Other processes (plant uptake, soil organic matter dynamics) must compensate in the field and keep soil nutrient concentrations at relatively low levels.
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    The influence of tillage and cropping-intensity on cereal response to nitrogen, sulfur, and phosphorus (1992)
    Springer
    Nutrient cycling in agroecosystems 31 (1992), S. 15-19 
    Details
    ISSN: 1573-0867
    Keywords: Tillage ; crop rotation ; cereal grain ; wheat ; nitrogen ; sulfur ; phosphorus ; no-till
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Efficient fertilizer use is a prerequisite for achieving optimum crop yield while avoiding environmental contamination. Cereal response to nitrogen (N), sulfur (S), and phosphorus (P) were determined for 6 years under differing tillage [conventional-till (CT) vs. no-till (NT)] and intensity of cropping (cereal/fallow vs. cereal/cereal). Semidwarf white winter wheat (Triticum aestivum L.) alternated yearly with either fallow or spring cereal [barley (Hordeum vulgare L.) or spring wheat] on a Typic Haploxeroll soil in a 415 mm rainfall zone. Fertilizer treatments were no fertilizer (None), N only (N), N plus S (NS), and N plus S plus P (NSP). Average application rate, when applied, was 109 kg N, 18 kg S, and 11 kg P ha−1. Average cereal yield without fertilizer was 1.82 t ha−1. Nitrogen increased grain yield in 6 of 6, S in 4 of 6, and P in 3 of 6 years, with P and S response significant the remaining years at the 10% probability level. Average yield increases were 1.11 t ha−1 for N, 0.93 t ha−1 for S, and 0.47 t ha−1 for P. The NT/CT yield ratio was 0.60, 0.75, 0.93, and 0.95 with None, N, NS, and NSP addition, respectively, indicating that N and S deficiency were more severe in no-till. Limited increase in the NT/CT ratio with P addition indicated that P deficiency was less affected by tillage. Winter wheat always yielded less under NT than CT regardless of fertility, whereas spring cereals reached equality when fertilized with NSP. Annually-cropped wheat yielded 52, 67, 89, and 90% of wheat after fallow with None, N, NS, and NSP, respectively. Thus N and S, but not P, deficiency was more intense with increased frequency of cropping. Adequate fertility was a prime prerequisite for efficient yield in all systems.
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    An economic evaluation of a long-term experiment on phosphorus and manure amendments to sandy Sahelian soils: Using a stochastic dominance model (1992)
    Springer
    Nutrient cycling in agroecosystems 33 (1992), S. 193-202 
    Details
    ISSN: 1573-0867
    Keywords: manure ; Niger ; phosphorus ; Sahelian soils ; stochastic dominance framework
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Poor fertility status of sandy Sahelian soils represents a major constraint to cereal and legume production. Soil amendment options were evaluated, using a stochastic efficiency framework. Dominance analyses showed that in the presence of annual applications of 30 kg N ha−1 and 30 kg K ha−1, efficient soil amendment options comprise of either the annual application of 8.7 kg P ha−1 in the form of single superphosphates in combination with 5 tonnes manure ha−1 applied every three years or the annual application of 17.5 kg P ha−1 in the form of single superphosphates. Choice between these two efficient options depends on the availability of manure, deficiencies in sandy soils and farmer resource endowments.
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    Ultrasonic absorption spectroscopy between 5 and 3100 MHz on some aqueous polyelectrolyte solutions (1992)
    Springer
    Colloid & polymer science 270 (1992), S. 982-989 
    Details
    ISSN: 1435-1536
    Keywords: Ultrasonic relaxation ; kinetics ; hydrogen bonds ; counterion interactions ; polyelectrolytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The ultrasonic absorption coefficient has been measured as a function of frequency between 5 MHz and 3.1 GHz for aqueous solutions of polyacrylic acid and of its sodium, potassium, and tetraethylammonium salts. Unlike an aqueous solution of propionic acid, all polymer solutions clearly exhibit excess absorption. Within the frequency range under consideration the excess absorption spectra can be analytically represented by two Debye-type relaxation terms. At 25°C the corresponding relaxation times adopt values between 3 and 12.4 ns, and between 0.12 and 0.22ns, respectively. The former process is discussed in accordance with previous models. The relaxation of the polyacrylic acid solutions is assumed to be related to the formation of hydrogen bonds of the polymeric molecules and that of the polyacrylate solutions may be due to interactions of counterions with chain segments. The latter process, the existence of which has been first proven in this study, is likely to reflect rotational motions of carboxyl groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00655967
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    Kinetic study of ion exchange reaction between lysozyme and carboxymethyl Sephadex C-25 (1992)
    Springer
    Colloid & polymer science 270 (1992), S. 878-884 
    Details
    ISSN: 1435-1536
    Keywords: Adsorption-desorptionkinetics ; kinetics ; ionexchange ; lysozyme ; Sephadex C-25
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The ion-exchange reaction of lysozyme with carboxymethyl Sephadex C-25 was followed by conductivity change as a function of time just after the rapid mixing of the protein solution with the Sephadex suspension. A single relaxation process was observed; the conductivity increased exponentially with time in the 100 s scale. In this process, protons were released from the Sephadex C-25 in the same time scale. The relaxation process slowed down with an increase in the lysozyme concentration, but it quickened upon the addition of HCl. On the other hand, the ζ potential on the Sephadex C-25 surface changed from a negative value to a positive one with an increase in the amount of lysozyme adsorbed on the surface. On the basis of these data, the relaxation process was attributed to the ion-exchange reaction of lysozyme with several protons of carboxymethyl groups of the Sephadex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00657732
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  • 92
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    A simplified cooperative model of stress relaxation and other consolidation processes in solids (1992)
    Springer
    Rheologica acta 31 (1992), S. 390-398 
    Details
    ISSN: 1435-1528
    Keywords: Bose-Einstein statistics ; relaxation ; aging ; kinetics ; relaxation time ; spectrum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract This paper explores the properties of a relaxation function derived from a differential equation mimicking the distribution mechanism of Bose-Einstein statistics in the time domain. Within a significant portion of the process, the relaxation quantity n decreases linearly with log time. The relation between dn/dt and n is an exponential one. In this respect, the present approach produces results largely equivalent to those obtained using the hypothesis of stress-dependent thermal activation or a box-like spectrum of relaxation times, τ. The τ spectrum of the model proposed here is discrete, with integer valued fractions of a characteristic -centering the equations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418337
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  • 93
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    Influence of the microorganism support on the kinetics of anaerobic fermentation of condensation water from thermally concentrated olive mill wastewater (1992)
    Springer
    Biodegradation 3 (1992), S. 93-103 
    Details
    ISSN: 1572-9729
    Keywords: anaerobic fermentation ; olive mill waste ; kinetics ; support
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two materials of different structure, sepiolite and bentonite, evaluated as supports for the microorganisms effecting anaerobic fermentation, behaved differently towards condensation water from thermally concentrated olive mill wastewater from a kinetic point of view. Assuming the overall anaerobic digestion process to conform to first-order kinetics, the apparent kinetic constant for the digester including sepiolite as support was 1.12 day-1, while that of the digester using the bentonite support was 0.73 day-1. Thus, the apparent kinetic constant of the process was increased by 35% with the use of sepiolite. The yield coefficient, Yp/s, was 0.344 and 0.318 litres CH4 STP/g COD for the sepiolite and bentonite supports respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189637
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  • 94
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    The effects of dredging and fish stocking on the trophic status of shallow, peaty ditches (1992)
    Springer
    Hydrobiologia 233 (1992), S. 225-233 
    Details
    ISSN: 1573-5117
    Keywords: ditches ; fish stock ; dredging ; biomanipulation ; eutrophication ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the polder ‘Wormer, Jisp and Nek’, which forms part of a grossly eutrophicated region in the province North Holland, the effects of dredging and biomanipulation were studied in ditches. Four areas, including 5.7 ha surface water in total, were dammed up and dredged. It was feasible to remove the loose top-layer of sediments with a high content of phosphorus by modifications of the dredging machine. In two areas the fish stock was managed. The measures resulted in an improvement of the water quality: an increase of the transparency and a decrease of suspended solids, phosphorus, nitrogen and algae. The chlorophyll-a concentration decreased nearly to 100 µg l−1 (summer average). The relative densities of diatoms, green algae and cyanobacteria did not change. The zooplankton community was dominated by small rotifers and crustaceans both before and after restoration measures. Cladocerans were scarcely present. In the second year after the measures, submerged macrophytes developed.
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    URL: http://dx.doi.org/10.1007/BF00016111
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  • 95
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    Phytoplankton and zooplankton population dynamics and production of a recently formed African reservoir (1992)
    Springer
    Hydrobiologia 237 (1992), S. 47-60 
    Details
    ISSN: 1573-5117
    Keywords: nitrogen ; phosphorus ; underwater light ; primary production ; secondary production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The study provides a 2.5 year record of Rhenosterkop Dam (KwaNdebele, South Africa) plankton population dynamics and production in relation to physical and chemical changes which occurred during the trophic depression and stabilization phases of the reservoir. The mean volume of the reservoir was 4% of full storage capacity. Water temperatures ranged from 14 °C to 27 °C. Due to inorganic suspensoids, the euphotic zone averaged 2.6 m. An anaerobic zone developed each summer. The nitrogen, soluble reactive phosphorus (SRP) and silica concentrations did not displaya seasonal pattern, but the latter two nutrients declined over the study. The dominant phytoplankton group was the cryptophytes while the zooplankton population was dominated by crustaceans. Chlorophyll a concentrations ranged from 1.1 to 27 mg m−3 and were positively correlated to silica and SRP concentrations and inversely with NH4-N concentrations. Primary production ranged from 22.6 to 375 mgC m−2 h−1; changes in Amax were positively correlated to silica and SRP concentrations. Total zooplankton dry weight biomass varied from 〈0.5 to 〉4 mg l−1. Annual zooplankton (secondary) production was 8 to ∼ 15 gC m−3 a−1; both primary and secondary production were greatest in the first 12 months of study and remained at low levels for the remainder, similar to the trends for silica and SRP. The data indicate that the reservoir shifted from eutrophic to mesotrophic during the study, typical of events in new reservoirs, and that changes in the plankton populations were largely the result of changing nutrient concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00008427
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  • 96
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    Cadmium, zinc, lead and copper inChironomus riparius (Meigen) larvae (Diptera, Chironomidae): uptake and effects (1992)
    Springer
    Hydrobiologia 241 (1992), S. 119-134 
    Details
    ISSN: 1573-5117
    Keywords: trace metals ; uptake ; kinetics ; development ; growth ; adsorption ; Chironomus riparius
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cadmium, Zn, Pb and Cu uptake and effects in larvae ofChironomus riparius (Meigen) were studied in an integrated laboratory investigation, in which metal analyses in different instar stages, uptake kinetics and effects on development and growth were considered in three separate experiments. In short-term experiments with fourth instar larvae, it was demonstrated that only a minor portion of metals was adsorbed on the larval exoskeletons. No conclusive evidence on the uptake mechanism was found, but active uptake of trace metals seemed highly unlikely. In partial life cycle experiments, all four metals studied were readily accumulated in chironomid larvae. Uptake could be described satisfactorily utilizing a first-order one-compartment uptake model which incorporated growth. In all cases steady state conditions were approached and high uptake and elimination rate constants were estimated. Distinct differences between essential (Zn and Cu) and non-essential (Cd and Pb) metals were noted. Larval growth was significantly impaired upon exposure. Finally, long-term exposure experiments with low Cd concentrations (0.010 and 0.025 mg 1−1) resulted initially in growth impairment and high mortality in first instar stages, but surviving larvae restored growth and adults emerged even before control adults. In similar experiments with Zn (0.1 and 1.0 mg 1−1), development of larvae was significantly retarded. High Zn concentrations in larvae were noted and almost no adult midges emerged.
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    URL: http://dx.doi.org/10.1007/BF00008264
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    Response of early and late semiarid seral species to nitrogen and phosphorus gradients (1992)
    Springer
    Plant and soil 140 (1992), S. 127-135 
    Details
    ISSN: 1573-5036
    Keywords: nitrogen ; phosphorus ; root: shoot ratios ; secondary succession ; semiarid ; shrubland ; tissue nitrogen ; tissue phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Above- and below-ground biomass production, nitrogen (N) and phosphorus (P) tissue concentrations, and root: shoot ratios were examined for five species that are characteristic of a semiarid successional sequence under controlled greenhouse conditions. In two simultaneous experiments, seedlings of one forb, two grass, and two shrub species important in a sagebrush successional sere, were subjected to seven levels of N and P. Results of the experiments suggest distinct differences in nutrient response patterns between early and late seral species. Early seral species produced more biomass but had lower tissue nutrient concentrations than late seral species. As N and P availabilities decreased, late seral species displayed characteristics indicative of increasing competitive advantage over those of early seral species. Root: shoot ratios of the five species primarily reflected patterns related to lifeform, but with some early and late seral characteristics. Results from this study 1) confirm that nutrient use pattern, nutrient availability, and seral position relationships characteristic of mesic ecosystems hold equally true for semiarid systems, and 2) suggest that nutrients are important organizing factors in semiarid ecosystems.
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    URL: http://dx.doi.org/10.1007/BF00012814
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    Stoichiometric relationships among producers, consumers and nutrient cycling in pelagic ecosystems (1992)
    Springer
    Biogeochemistry 17 (1992), S. 49-67 
    Details
    ISSN: 1573-515X
    Keywords: algae ; nitrogen ; nutrient ; phosphorus ; regeneration ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Most ecosystem models consolidate members of food-webs, e.g. species, into a small number of functional components. Each of these is then described by a single state variable such as biomass. When a multivariate approach incorporating multiple substances within components is substituted for this univariate one, a ‘stoichiometric’ model is formed. Here we show that the Nitrogen:Phosphorus ratio within zooplankton herbivores varies substantially intraspecifically but not intraspecifically. By using stoichiometric theory and recent measurements of the N:P ratio within different zooplankton taxa, we calculate large differences in ratios of nutrients recycled by different zooplankton species. Finally, we demonstrate that N:P stoichiometry can successfully account for shifts in N- and P-limitation previously observed in whole-lake experiments. Species stoichiometry merges food-web dynamics with biogeochemical cycles to yield new insights.
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    URL: http://dx.doi.org/10.1007/BF00002759
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  • 99
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    Comparison of specific rates of hybridoma growth and metabolism in batch and continuous cultures (1992)
    Springer
    Cytotechnology 10 (1992), S. 147-155 
    Details
    ISSN: 1573-0778
    Keywords: batch culture ; continuous culture ; hybridoma ; kinetics ; specific rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract For the mouse hybridoma cell line VO 208, kinetics of growth, consumption of glucose and glutamine, and production of lactate, ammonia and antibodies were compared in batch and continuous cultures. At a given specific growth rate, different metabolic activities were observed: a 40% lower glucose and glutamine consumption rate, but a 70% higher antibody production rate in continuous than in batch culture. Much higher metabolic rates were also measured during the initial lag phase of the batch culture. When representing the variation of the specific antibody production rate as a function of the specific growth rate, there was a positive association between growth and antibody production in the batch culture, but a negative association during the transient phase of the continuous culture. The kinetic differences between cellular metabolism in batch and continuous cultures may be result of modifications in the physiology and metabolism of cells which, in continuous cultures, were extensively exposed to glucose limitations.
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    URL: http://dx.doi.org/10.1007/BF00570891
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  • 100
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    Nutrient and hydrologic budgets of a great lakes coastal freshwater wetland during a drought year (1992)
    Springer
    Wetlands ecology and management 1 (1992), S. 211-222 
    Details
    ISSN: 1572-9834
    Keywords: freshwater marsh ; freshwater wetland ; Great Lakes ; hydrology ; phosphorus ; water quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A coastal wetland along Lake Erie (Ohio, U.S.A.) was studied to determine hydrologic and phosphorus budgets and spatial and temporal variation of phosphorus and related chemical parameters. The wetland was influenced by changing Lake Erie water levels, seiches, shifting shoreline sediments, and watershed inflow during a year of severe drought. The water budget for a 7-month period (March – September, 1988) had average inflow of 15 200 m3 day−1 from the watershed and 3.5 m3 day−1 from Lake Erie. The wetland increased in volume by 700 m3 day−1 despite a drought that resulted in 80% more evapotranspiration than rainfall as a barrier beach isolated the wetland from Lake Erie for 77% of the study period. Conductivity decreased by 34% as water flowed through the wetland and turbidity and total suspended solids were variable and statistically similar at inflow and outflow. Average total phosphorus concentrations in the inflow and outflow were also similar (247 and 248 µg P l−1 respectively) although total soluble phosphorus and soluble reactive phosphorus decreased significantly (α=0.05) from inflow to outflow (averages 94 to 45 µg P l−1 and 7.5 to 4.0 µg P l−1 respectively). Nutrient budgets from field data estimate a retention of 36% of the phosphorus, presumably in the sediments (0.8 mg P m−2 day−1). A general nutrient retention model, an estimated deposition rate from a sediment core and a simulation model predicted higher mass retention of phosphorus but similar percentage retention. Sommaire Un marecage qui côtoie le lac Erie (USA) a servi de site expérimental pour en déterminer les budgets d'eau et de phosphore, de même que pour la variation spatiale et temporelle du phosphore et d'autres facteurs chimiques. Le marécage a été influencé par: niveaux d'eau qui changeaient; seiches; sédiments mouvants du littoral; et afflux de la ligne de partage des eaux dans une année de grande sécheresse. Le budget d'eau dans une période de 7 mois (mars–septembre 1988) montre un afflux de 15 200 m3 jour−1 de la ligne de partage, et 3.5 m3 jour−1 du lac Erie. Le volume du marécage a augmenté par 700 m3 jour−1 malgré une sécheresse qui a produit plus d'évapotranspiration (80%) que de pluie pendant qu'une plage-obstacle a isolé le marecage du lac Erie pendant 77% de la période d'observation. La conductivité a diminué par 34% pendant que l'eau coulait, et la turbidité et les TSS ont varié, tout en démontrant des statistiques similaires à l'afflux et au déversement. Les moyennes pour les concentrations du total du phosphore à l'afflux et au déversement ont été similaires (247 and 248 µg P l−1), quoique le TSP et le SRP ont diminué (α=0.05) de l'afflux au déversement (donant des moyennes de 94 à 45 µg P l−1 et de 7.5 à 4.0 µg P l'−1). Les budgets de substances nutritives pour les données suggèrent une reténtion de 36% du phosphore, évidemment dans les sédiments (0.8 mg P m−2 jour−1). Un modèle pour la rétention des nutrients, un taux de déposition, estimé par un noyau de sédiments, et une simulation avaient prédit un plus grand taux de rétention de phosphore, mais un pourcentage similaire pour la rétention.
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    URL: http://dx.doi.org/10.1007/BF00244926
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