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  • 1
    Electronic Resource
    Electronic Resource
    Determination of methylmercury in biological samples by semiautomated headspace analysis (1985)
    s.l. : American Chemical Society
    Analytical chemistry 57 (1985), S. 2788-2791 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00291a011
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  • 2
    Electronic Resource
    Electronic Resource
    Seasonal variation of phytoplankton community structure and nitrogen uptake regime in the Indian Sector of the Southern Ocean (1998)
    Springer
    Polar biology 20 (1998), S. 259-272 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study investigates the dynamics of phytoplankton communities and nitrogen uptake in the Indian sector of the Southern Ocean during spring and summer. The study area is oligotrophic (Chl a stocks 〈50 mg m−2); nevertheless, a large spatial variation of phytoplankton biomass and community structure was observed. During both seasons the phytoplankton community in the seasonal ice zone showed higher biomasses and was mainly composed of large diatom cells. However, in the permanently open ocean zone the community had low biomass and was chiefly composed of nano- and picoflagellates. In the polar front zone, although biomass was higher, the community structure was similar to the open ocean zone. The results suggest that the variation in phytoplankton community structure on a larger scale resonates with gradients in water column stability and nutrient distribution. However, significant changes in biomass and nutrient stocks but little change in community structure were observed. Absolute nitrogen uptake rates were generally low, but their seasonal variations were highly significant. During spring the communities displayed high specific nitrate uptake (mean rate = 0.0048 h−1), and diatoms (in the seasonal ice zone) as well as nano- and picoflagellates (in the permanently open ocean zone and polar front zone) were mainly based on new production (mean ƒ-ratio = 0.69). The transition to summer was accompanied by a significant reduction in nitrate uptake rate (0.0048 h−1 → 0.0011 h−1) and a shift from predominantly new to regenerated production (ƒ-ratio 0.69 → 0.39). Ammonium played a major role in the seasonal dynamics of phytoplankton nutrition. The results emphasize that, despite a large contrast in community structure, the seasonal dynamics of the nitrogen uptake regime and phytoplankton community structure in all three subsystems were similar. Additionally, this study supports our previous conclusion that the seasonal shift in nitrogen uptake regime can occur with, as well as without, marked changes in community structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050302
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  • 3
    Electronic Resource
    Electronic Resource
    Intense nutrient removal in the remote area off Larsen Ice Shelf (Weddell Sea) (2000)
    Springer
    Polar biology 23 (2000), S. 85-94 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using Weddell Sea data collected during a cruise with “FS Polarstern” in austral summer 1992/1993, depletions of nutrients and TCO2 in the summer surface layer were calculated. The analogous depletion-like properties for temperature (Heat Storage) and salinity were also computed. The latter properties are useful to describe the physical conditions over the time period pertinent to the depletions. For different areas a strong correlation exists of Heat Storage and nutrient/TCO2 depletions, which is caused by a common factor – the period of light availability. Offshore of the Larsen shelf, an area usually inaccessible due to perennial ice cover, high nutrients/TCO2 depletions are achieved over a short period of time, pointing to a rapidly producing biological system. Primary productivity, calculated from the TCO2 depletion, amounts to about 100 mg C m−2 day−1 for the central Weddell Sea, but 570–1140 mg C m−2 day−1 for the offshore Larsen region. These values agree fairly well with the open-ocean Antarctic and other coastal areas, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050012
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  • 4
    Electronic Resource
    Electronic Resource
    General description of the Scheldt estuary (1997)
    Springer
    Hydrobiologia 366 (1997), S. 1-14 
    Details
    ISSN: 1573-5117
    Keywords: Scheldt estuary ; description ; hydrology ; sedimentation ; oxygen profiles ; productivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A general description of the Scheldt estuary,including the hydrology, the sediment transport, theproductivity and the biodegradation with respect totheir influence on the trace metal behaviour in theScheldt estuary, is given. The river basin can be divided in several sectionsaccording to their morphological, hydrodynamical andsedimentary properties. The zone from km 78 to 55,which corresponds roughly with the salinity zone from2 to 10 psu, is the zone of high turbidity, highsedimentation and of oxygen depletion, especially inthe summer period. That area is called the geochemicalfilter because the solid/dissolved distribution of thetrace metals is controlled by redox,adsorption/desorption, complexation andprecipitation/coprecipitation processes. Thesedimentation rate in that area is estimated at280 Mkg y-1. In the downstream estuary the phytoplankton activityincreases due to the restoration of oxygen and to themuch lower turbidity values. That area is called thebiological filter because incorporation of tracemetals by the plankton communities lowers the tracemetal concentrations during the productivity period,while transformation of metal species, especiallyobserved with mercury, occurs during that period too.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003164009031
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of organic complexation on the behaviour of dissolved Cd, Cu and Zn in the Scheldt estuary (1997)
    Springer
    Hydrobiologia 366 (1997), S. 81-90 
    Details
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Samples from the Scheldt estuary have been assayed for dissolved Cd, Cuand Zn using differential pulse anodic stripping voltammetry, either astotal (after UV irradiation) or labile concentrations. Under theseexperimental conditions, labile concentrations ranged between51–65% of total Cu, 16–66% of total Zn and53–91% of total Cd. The metal–organic interactions wereassessed by evaluating (a) the distribution coefficient Kd forthe distribution of the metals between the liquid phase (complexation) andtheir binding to particulate matter, and (b) the competitive effect exertedby inorganic complexing ligands using a multi–element interactionmodel. The proportion of organically bound metals (strong and labile) wasestimated, in this speciation scheme, to range from 86 to 99% for Cu,from 90 to 96% for Zn, and from 10 to 35% for Cd. From thedissolved organic carbon distribution in the Scheldt (≤ 10 mg Cl-1 and taking into account competition from major cations Caand Mg, free ligand concentrations available for heavy metal complexationwere estimated to be ≤ 0.15 mg C l-1. With these values,conditional stability constants for the chelation of Cu, Zn and Cd werecalculated assuming either a single-step or a two-step complexation in thedissolved phase. Given the assumptions made in these models, stabilityconstants in the range of 107.8–1010.6 forCu, 107.0–109.1 for Zn and106.9–108.9 for Cd were obtained. Therelevance of these data to previous in vitro and in situ studies isdiscussed taking into consideration current concepts of metal bindingaffinity for organic ligands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003176327686
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  • 6
    Electronic Resource
    Electronic Resource
    Biogeochemical behaviour of Cd, Cu, Pb and Zn in the Scheldt estuary during the period 1981–1983 (1997)
    Springer
    Hydrobiologia 366 (1997), S. 15-44 
    Details
    ISSN: 1573-5117
    Keywords: Scheldt estuary ; trace metals ; 1981–1983 ; dissolved ; particulate ; biogeochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cu, Zn, Cd and Pb have been analysed in suspendedmatter and water samples from the Scheldt estuary,collected during five cruises between May 1982 and May1983. In order to evaluate the overall metal behaviourin the estuary, continuous longitudinal profiles ofthe total, the particulate and the dissolved metalconcentrations are discussed in relation to variousspecific physico-chemical parameters. By means ofcorrelation and multi-regression techniques, severalestuarine processes could be identified which dominateand/or control the behaviour of the individual tracemetals in three distinct areas of the Scheldt estuary. The behaviour of the four selected metals was foundto show some common features, but is besides this alsocharacterised by many individual and specificproperties. The total metal concentrations seem toco-vary well with the turbidity in the maximumturbidity zone between salinities 2 and 10 psu. In thedownstream area a dilution profile is observed for thetotal metal concentrations of Cu and Cd as well as forthe dissolved concentrations of all metals. Dissolved metal production rates are high for Cu andCd, but much lower for Zn and Pb, confirming thedifferent longitudinal dissolved metal profiles. ForCu and Cd these dissolved metal profiles arecharacterised by a broad mobilisation area, coveringthe whole middle estuary. Pb on the other hand, showsa more confined mobilisation area, and for Zn no sucharea was found. During winter the dissolved metalproduction rates seem to be controlled, predominantly,by desorption processes. During summer dissolved metalproduction is correlated mainly to the dissolvedoxygen content, suggesting the domination of redoxprocesses solely or in combination with desorptionprocesses. In some cases, co-existent with nearly zerooxygen concentrations, removal of dissolved metals wasobserved, possibly reflecting precipitation reactions. Longitudinal particulate metal profiles all show anegative deviation versus the dilution profile. Cu andCd provide the higher deviations, characterised by anarrow enrichment zone preceding a broad mobilisationarea. Finally, all particulate metal profiles appearedto correlate well with POC, when expressed involumetric units.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003168125869
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  • 7
    Electronic Resource
    Electronic Resource
    Contribution of nitrate to the uptake of nitrogen by phytoplankton in an ocean margin environment (1997)
    Springer
    Hydrobiologia 353 (1997), S. 139-152 
    Details
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rates of nitrate and ammonium uptake by phytoplankton were measured fromJuly 1990 to March 1995 in the surface waters at several stations locatedalong the continental margin of the NE Atlantic Ocean. Total inorganicnitrogen assimilation ranged from 2.3 to 95 nM h−1 andexhibited two maxima during the spring bloom and in fall at the beginning ofthe vertical mixing of the water column. Seasonal and spatial changes in thenitrogen uptake regime (f-ratios) were estimated (1) by correcting ammoniumuptake rates with an isotope dilution model, and (2) by evaluating theinhibition of nitrate uptake by ammonium, using a variation of theMichaelis-Menten equation. Overall, nitrate uptake rates paralleled carbonfixation rates, and f-ratios followed the well-known function of nitrate.During spring, new production, sensu Dugdale & Goering (1967), accountedfor 46 to 85% of the total inorganic nitrogen production. It can gainin importance through vertical mixing in fall (0.29 〈 f 〈 0.82), aftera period of predominant regenerated production in summer (0.07 〈 f 〈0.41). Although new production appeared to be quantitatively important onaverage (mean f = 0.53), kinetic data suggested that ammonium wasutilised preferentially throughout the full spectrum of nitrogenconcentrations observed during this study. Moreover, the inhibition ofnitrate uptake by ambient level of ammonium was estimated to range from 8 to50%. Therefore, it is suggested that the supply of regeneratednitrogenous nutrients, combined with feedback mechanisms (preference andinhibition), triggers a switch-over from predominantly new productiontowards regenerated production, even before the complete exhaustion ofnitrate in the surface water. Overall, these results indicate a leading rolefor ammonium in regulating the removal of nitrate in this margin ecosystem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003058928157
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  • 8
    Electronic Resource
    Electronic Resource
    The biogeochemical behaviour of Cd, Cu, Pb and Zn in the Scheldt estuary: results of the 1995 surveys (1997)
    Springer
    Hydrobiologia 366 (1997), S. 45-62 
    Details
    ISSN: 1573-5117
    Keywords: Scheldt estuary ; trace metals ; 1995 ; dissolved ; particulate ; biogeochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cu, Cd, Zn and Pb concentrations in both dissolved andparticulate phase were assessed during 1995. DataQuality Assurance was an integral part of this studyand involved all major steps of the analysis proceduresuch as sampling, sample handling, preconcentrationand determination. Desorption and redox processes clearly control thedissolved Cu and Cd profiles. Mobilisation ofdissolved Zn is small and essentially restricted tothe low salinity area and the late spring survey.Dissolved Pb shows the clearest dilution pattern. Theparameters representative of these processes(dissolved oxygen and salinity) also correlate verywell with the particulate metal profiles. In addition, the plankton activity (expressed by thechlorophyll-a levels) may influence the dissolved andparticulate metal profiles. In combination withdesorption and redox processes, seasonal variationswere induced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003120226778
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  • 9
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    Dioxin and Dioxin-Like Activity in Sediments of the Belgian Coastal Area (Southern North Sea) (2007)
    Springer
    Details
    Publication Date: 2007-02-05
    Print ISSN: 0090-4341
    Electronic ISSN: 1432-0703
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Published by Springer
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  • 10
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    Microwave digestion of organic substances, a useful tool for dissolved organic nitrogen measurements (1999)
    Elsevier
    Details
    Publication Date: 1999-02-01
    Print ISSN: 0043-1354
    Electronic ISSN: 1879-2448
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Elsevier
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