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  • Articles  (20)
  • Geochemistry  (12)
  • hydrology  (8)
  • 2000-2004  (20)
  • 1960-1964
  • 1950-1954
  • Geosciences  (20)
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  • Articles  (20)
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  • 1
    Electronic Resource
    Electronic Resource
    Shallow pore water sampling in reef sediments (2000)
    Springer
    Coral reefs 19 (2000), S. 93-97 
    Details
    ISSN: 1432-0975
    Keywords: Key words Sampling ; Sediment ; Geochemistry ; Pore water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Several new techniques have been developed to allow the geochemical characterization of shallow pore waters in reefs. First, a new method was developed for using non-metallic well-points to sample pore waters from shallow depths (〈1 m) in coral reefs with unconsolidated substrates. These PVC well-points can be made faster and at less expense than well-points made of stainless steel. They also eliminate metal contamination and are free from the problems of corrosion in sea water. Additional improvements in sampling techniques maximize the spatial resolution of geochemical gradients and address the problems of atmospheric contamination associated with the sampling of dissolved gases. Data taken from Checker Reef, Oahu, Hawaii, illustrate the application of these methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003380050233
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  • 2
    Electronic Resource
    Electronic Resource
    Geochemistry, petrogenesis and tectonic setting of late Neoproterozoic Dokhan-type volcanic rocks in the Fatira area, eastern Egypt (2000)
    Springer
    International journal of earth sciences 88 (2000), S. 764-777 
    Details
    ISSN: 1437-3262
    Keywords: Key words Neoproterozoic ; Dokhan volcanics ; Egypt ; Geochemistry ; Petrogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The Neoproterozoic Dokhan volcanics of the Fatira area in eastern Egypt comprise two main rock suites: (a) an intermediate volcanic suite, consisting of basaltic andesite, andesite, dacite, and their associated pyroclastic rocks; and (b) a felsic volcanic suite composed of rhyolite and rhyolitic tuffs. The two suites display well-defined major and trace element trends and a continuum in composition with wide ranges in SiO2 (54–76%), CaO (8.19–0.14%), MgO (6.96–0.04%), Sr (983–7 ppm), Zr (328–95 ppm), Cr (297–1 ppm), and Ni (72–1 ppm). They are enriched in LILEs (Rb, Ba, K, Th, Ce) relative to high field strength elements (Nb, Zr, P, Ti) and show strong affinity to calc-alkaline subduction-related rocks. However, their undeformed character, their emplacement temporally and spatially with post-orogenic A-type granite, and their high Zr/Y values suggest that their emplacement follow the cessation of subduction in eastern Egypt in an extensional-related within-plate setting. Major and trace element variations in the intermediate volcanics are consistent with their formation via partial melting of an enriched subcontinental lithospheric mantle source followed by a limited low-pressure fractional crystallization of olivine and pyroxene before emplacement. The LILE enrichment relative to HFSE is attributed to the inheritance of a subduction component from mantle material which constituted the mantle wedge during previous subduction events in eastern Egypt. The evolution of the whole volcanic spectrum was governed mainly by crystal/melt fractionation of amphibole, plagioclase, titanomagnetite, and apatite in the intermediate varieties and plagioclase, amphibole, biotite, Fe–Ti oxides, apatite, and zircon in the felsic varieties. At each stage of evolution, crystal fractionation was accompanied by variable degrees of crustal contamination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005310050304
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  • 3
    Electronic Resource
    Electronic Resource
    Zircon ages and Nd isotopic and chemical compositions of orthogneisses from the Black Forest, Germany: evidence for a Cambrian magmatic arc (2000)
    Springer
    International journal of earth sciences 88 (2000), S. 791-802 
    Details
    ISSN: 1437-3262
    Keywords: Key words Variscan belt ; Moldanubian zone ; Black Forest ; Orthogneiss ; Zircon dating ; ¶Nd isotopes ; Geochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Single zircon U–Pb dating combined with 207Pb/206Pb ages obtained by the evaporation method constrains the emplacement of tonalitic, trondhjemitic, and granodioritic orthogneisses of the Moldanubian zone in the Black Forest between 500 and 510 Ma. Two detrital zircon populations of 1.9 and 1.6 Ga indicate Early-Middle Proterozoic material in the former setting of the basement. The initial eNd values range from –0.1 to –3.4 and mean crustal residence ages of 1.0–1.4 Ga are consistent with involvement of Early-Middle Proterozoic crust, and a subordinate juvenile component probably originating from subduction-related melting of the mantle. The orthogneisses have fractionated REE patterns and slightly higher K2O/Na2O ratios than typical low-K tonalite–trondhjemite–granite suites. The chemical data are interpreted as evidence for melting of amphibolite and contributions from evolved crust. The emplacement of the orthogneisses was superceded by a high-temperature metamorphic event at ∼480 Ma which we interpret as a result of lithospheric thinning in a marginal basin behind a Cambrian magmatic arc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005310050306
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  • 4
    Electronic Resource
    Electronic Resource
    Upper Neoproterozoic–Lower Cambrian sedimentary successions in the Central Iberian Zone (Spain): sequence stratigraphy, petrology and chemostratigraphy. Implications for other European zones (2000)
    Springer
    International journal of earth sciences 89 (2000), S. 2-20 
    Details
    ISSN: 1437-3262
    Keywords: Lithostratigraphy ; Petrology ; Geochemistry ; Sedimentology ; Sequence stratigraphy ; Late Neoproterozoic ; Lower Cambrian ; Central Iberian Zone ; Iberian Massif
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: 2 O3, TiO2, Zr, and Nb abundances in shales from all the units, strongly suggest a gradual compositional change within this sedimentary succession. Together with the petrological data, the chemical results do not reveal any obvious coeval volcanic contribution to the sediments. On the basis of the chemical data, a comparison is made with other European zones containing detrital sediments composed of reworked crustal components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005310050314
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  • 5
    Electronic Resource
    Electronic Resource
    Some constraints on geochemical features in the Triassic mantle of the easternmost Austroalpine–Southalpine domain: evidence from the Karawanken pluton (Carinthia, Austria) (2000)
    Springer
    International journal of earth sciences 89 (2000), S. 40-51 
    Details
    ISSN: 1437-3262
    Keywords: Karawanken pluton ; Eastern Alps ; Triassic ; Petrology ; Geochemistry ; Rb ; Sr age ; Triassic mantle ; Transtensional ; extensional tectonics ; Mesozoic rifting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005310050316
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  • 6
    Electronic Resource
    Electronic Resource
    Geochemical compositional changes at the Pliocene–Pleistocene transition in fluviodeltaic deposits in the Tegelen-Reuver area (southeastern Netherlands) (2000)
    Springer
    International journal of earth sciences 89 (2000), S. 154-169 
    Details
    ISSN: 1437-3262
    Keywords: Geochemistry ; Clay mineralogy ; Weathering ; Diagenesis ; Rhine ; Facies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: 2 O contents, which can be attributed to the Alpine source supplying fresh, sodic plagioclase-rich material instead of the local, strongly weathered sediments. Increasing K2O/Al2O3 can be attributed to a similar decrease in degree of weathering. However, this trend is disturbed by the loss of K from clay minerals during weathering in organic-rich layers. Local high TiO2 anomalies, caused by preferential sorting and concentration, are found in most Pliocene sections, but they are absent in the Upper Pliocene and Lower Pleistocene Alpine-derived deposits. This change is probably due to a change in the energy of the fluvial system. Finally, (pyrite-) S contents drop (siderite-) Fe contents rise. Micromorphological observations indicate that the Pliocene pyrite was formed when freshwater deposits were flooded with seawater during short-term events. The decrease in S, and the increase in siderite-Fe, can be attributed to decreasing marine influence, as a result of the marine regression at the Pliocene–Pleistocene transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005310050323
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  • 7
    Electronic Resource
    Electronic Resource
    Relics of an early-Panafrican metabasite–metarhyolite formation in the Brno Massif, Moravia, Czech Republic (2000)
    Springer
    International journal of earth sciences 89 (2000), S. 328-335 
    Details
    ISSN: 1437-3262
    Keywords: Key words Central European Variscides ; Brno Massif ; Metarhyolite ; Metabasite complex ; Geochemistry ; Zircon geochronology ; Cadomian ; Panafrican
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Brno Massif in Moravia, Czech Republic, is an important exposure of Precambrian basement in central Europe. It includes large volumes of Cadomian granitoids and a narrow fault-bounded zone with metagabbros, metadiorites, and metabasalts. This so-called Central Basic Belt also contains some metarhyolites; one of these was dated by means of the zircon evaporation method at 725 ±15 Ma. Chemical and isotope data show that the dated rock represents a mantle-derived magma which is cosanguinous with surrounding MORB-type metabasites. The data suggest that the Brno Massif hosts the oldest metabasite complex currently known in central Europe. Its formation apparently coincides with the main period of ocean-floor spreading and island-arc formation in the Panafrican orogens. This lends further support to the theory that the Brno Massif is a Gondwana-derived element.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005310000084
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  • 8
    Electronic Resource
    Electronic Resource
    GCM-simulated hydrology in the Arctic duringn the past 21,000 years (2000)
    Springer
    Journal of paleolimnology 24 (2000), S. 15-28 
    Details
    ISSN: 1573-0417
    Keywords: Last Glacial Maximum ; Arctic ; paleoclimatology ; Holocene ; climate modeling ; hydrology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The Paleoclimates from Arctic Lakes and Estuaries (PALE) project has chosen to conduct high resolution data-model comparisons for the Arctic region at 21 and 10 (calendar) ka BP. The model simulations for 21, 10, and 0 ka BP were conducted with the GENESIS 2.0 GCM. The 10 ka BP simulation was coupled to the EVE vegetation model. The primary boundary conditions differing from present at 21 ka BP were the northern hemisphere ice sheets and lower CO2, and at 10 ka BP were the orbital insolation and smaller northern hemisphere ice sheets. The purpose of this article is to discuss the hydrological consequences of these simulations. At the Last Glacial Maximum (21 ka BP) the large ice sheets over North America and Eurasia and the lower CO2 levels produced a colder climate than present, with less precipitation throughout the Arctic, except where circulation was altered by the ice sheets. At 10 ka BP greater summer insolation resulted in a warmer and wetter Beringia, but conditions remained cold and dry in the north Atlantic sector, in the vicinity of the remnant ice sheets. Less winter insolation at 10 ka BP resulted in colder and drier conditions throughout the Arctic. Precipitation - evaporation generally correlated with precipitation except where changes in the surface type (ice sheets, vegetation at 10 ka BP, or sea level at 21 ka BP) caused large changes in the evaporation rate. The primary hydrological differences (from present) at 21 and 10 ka BP correlated with the temperature differences, which were a direct result of the large-scale boundary condition changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008161631633
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  • 9
    Electronic Resource
    Electronic Resource
    Late quaternary paleoclimatic reconstructions for interior Alaska based on paleolake-level data and hydrologic models (2000)
    Springer
    Journal of paleolimnology 24 (2000), S. 29-41 
    Details
    ISSN: 1573-0417
    Keywords: Alaska ; hydrology ; evapotranspiration ; paleoprecipitation ; paleoclimates ; lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Hydrologic models are developed for two lakes in interior Alaska to determine quantitative estimates of precipitation over the past 12,500 yrs. Lake levels were reconstructed from core transects for these basins, which probably formed prior to the late Wisconsin. Lake sediment cores indicate that these lakes were shallow prior to 12,500 yr B.P. and increased in level with some fluctuation until they reached their modern levels 4,000-8,000 yr B.P. Evaporation (E), evapotranspiration (ET), and precipitation (P) were adjusted in a water-balance model to determine solutions that would maintain the lakes at reconstructed levels at key times in the past (12,500, 9,000 and 6,000 yr B.P.). Similar paleoclimatic solutions can be obtained for both basins for these times. Results indicate that P was 35-75% less than modern at 12,500 yr B.P., 25-45% less than modern at 9,000 yr B.P. and 10-20% less than modern at 6,000 yr B.P. Estimates for E and ET in the past were based on modern studies of vegetation types indicated by fossil pollen assemblages. Although interior Alaska is predominantly forested at the present, pollen analyses indicate tundra vegetation prior to about 12,000 yr B.P. The lakes show differing sensitivities to changing hydrologic parameters; sensitivity depends on the ratio of lake area (AL) to drainage basin (DA) size. This ratio also changed over time as lake level and lake area increased. Smaller AL to DA ratios make a lake more sensitive to ET, if all other factors are constant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008113715703
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  • 10
    Electronic Resource
    Electronic Resource
    Paleohydrology inferred from diatoms in northern latitude regions (2000)
    Springer
    Journal of paleolimnology 24 (2000), S. 93-107 
    Details
    ISSN: 1573-0417
    Keywords: paleohydrology ; lake level ; lake depth ; diatoms ; subarctic ; arctic ; hydrology ; lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Several recent studies have successfully applied diatom-based paleolimnological techniques to infer past hydrological changes in arctic and subarctic regions. For example, we summarize arctic studies that attempt to determine changes in peat water content, flood frequency, river discharge, effective moisture and ice cover in northern regions. Some of the investigations are still in preliminary stages, but represent innovative approaches to study arctic and subarctic paleohydrology. New data demonstrate that lake depth, which may be related to changing hydrological conditions, is a significant variable influencing the distributions of diatom taxa in lake surface sediment calibration sets from Wood Buffalo National Park (WBNP), on the border of Alberta and the Northwest Territories, Canada, and from Fennoscandia (mainly northwest Finland). Weighted averaging regression and calibration methods were used to develop quantitative inference models for lake depth using diatom assemblages preserved in surface sediments. The predictive abilities of the transfer functions were relatively high (for WBNP r2 = 0.70 and RMSE = 2.6 m, and for Fennoscandia r2 = 0.88 and RMSE = 1.8 m). However, evaluating the transfer functions using jack-knifing procedures indicated lower predictive abilities, possibly reflecting the relatively small sample size and/or short gradients used in these calibration sets. Such transfer functions can be used to track overall trends in lake levels, and provide an objective assessment as to directions of changing lake levels. Any interpretations of inferred lake levels, especially those related to climate change, must be made cautiously and must include some understanding of the local, present-day hydrological system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008173901591
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  • 11
    Electronic Resource
    Electronic Resource
    The late Holocene paleohydrology of Pine Lake, Alberta: a multiproxy investigation (2000)
    Springer
    Journal of paleolimnology 24 (2000), S. 427-441 
    Details
    ISSN: 1573-0417
    Keywords: late-Holocene ; water chemistry ; bison ; aspen ; fire regime ; pollen ; mineralogy ; granulometry ; hydrology ; Great Plains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract This paper reports on a high-resolution, multi-proxy, late-Holocene study from a lake in the Aspen Parkland of southern Alberta, Canada. A sediment core spanning the last 4000+ yrs from Pine Lake was analyzed for charcoal, granulometry, grain roundness, tephra content, geochemistry, mineralogy and pollen. This multi-proxy record indicates: (1) increasing anoxia causing a shift in S deposition from gypsum to pyrite due to increasing moisture availability in the late Holocene; (2) a decrease in Mg flux into the lake due to the development of the aspen forest, which reduced water flow through the Mg-rich shallow sand aquifer; the aspen forest expansion was in turn induced by the extirpation of plains bison prior to settlement; and (3) a change in the upland fire regime from frequent low-biomass grass fires to less frequent but higher biomass under-story fires, also as a result of the expansion of the aspen forest. Not only are the different proxies sensitive to different rates and magnitudes of change, they also show different sensitivities to different types of hydrological change: the mineralogy and geochemistry are sensitive to changes in water level and redox potential, and to changes in the relative strengths of the aquifers feeding the lake, while the granulometry is sensitive to total hydrological balance. Thus, apparently contradictory proxy results should be viewed as complementary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008155622656
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  • 12
    Electronic Resource
    Electronic Resource
    Geochemical background – can we calculate it? (2000)
    Springer
    Environmental geology 39 (2000), S. 990-1000 
    Details
    ISSN: 1432-0495
    Keywords: Key words Background ; Data distribution ; Normal distribution ; Log-normal distribution ; Geochemistry ; Environmental science ; Robust geostatistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The term "background" is discussed and a definition is suggested to put an end to the currently unsatisfying (non-)definition of geochemical or natural background. Based on the requirements stated in the definition, several simple and robust statistical methods are applied to different data sets (n〉50) from the atmosphere, pedosphere, and biosphere in order to explore their potential for the evaluation of a useful and robust background. Compared with the original data set both the calculated distribution, based upon the lower 50% of the values, as well as a 2σ-approximation of the normalised data set lead to promising and realistic results. Both methods seem appropriate for a fast and reliable evaluation of likely upper limits of background values. Nevertheless, even this robust method is not able to present absolute and doubtlessly correct background values. True quantification of any natural or geochemical background still requires a thorough investigation and is impossible without costly expert knowledge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002549900084
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  • 13
    Electronic Resource
    Electronic Resource
    Pit lakes: their characteristics and the potential for their remediation (2000)
    Springer
    Environmental geology 39 (2000), S. 1254-1260 
    Details
    ISSN: 1432-0495
    Keywords: Key words Mine ; Pit lake ; Geochemistry ; Remediation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Pit lakes form when open-pit mining operations are discontinued and dewatering ceases. The increase in open-pit metal mining since the 1970s will lead to the formation of numerous pit lakes over the next 50 years. Many of these lakes will develop acid sulfate conditions with high levels of dissolved metals. Approaches to remediation of these conditions that have been recommended include the addition of lime or other alkaline materials and the stimulation of sulfate-reducing bacteria. However, prevention rather than remediation is probably the preferable approach. Measures to prevent oxidation of mining waste and wall rocks, including measures to fill pits quickly with water, to inhibit the activity of acidophilic sulfur-oxidizing bacteria, and to promote anoxic conditions at the lake bottoms may minimize the formation of acids and dissolved metals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002549900100
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  • 14
    Electronic Resource
    Electronic Resource
    Geographical variations of trace elements in sediments of the major rivers in eastern China (2000)
    Springer
    Environmental geology 39 (2000), S. 1334-1340 
    Details
    ISSN: 1432-0495
    Keywords: Keywords China ; Geochemistry ; River ; Sediment ; Trace metals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  A total of 26 geographically and hydrologically diverse sediment samples were collected from 12 major rivers in eastern China. The 〈63-μm fraction of the sediments was analysed for both total concentrations of Cu, Zn, Pb and Cd, and their associations with various geochemical phases. The geographical variations of sediment-bound trace metals can be related to the bedrock types and weathering processes in the corresponding river basins. The rivers in southern China had notably higher concentrations of trace metals in sediments because of abundant non-ferrous mineral deposits and stronger weathering process in the region. A large proportion of trace metals in these sediments was associated with iron and manganese oxides and organic matter. Relative low levels of trace metals were found in river sediments in northern China, and a significant proportion of the metals was bound to organic matter, carbonates, and the residual fraction. The sediments in the Yellow River, originating from special loess, had the lowest concentrations of trace metals. Most of the trace metals were associated with the carbonates and residual phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002540000224
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  • 15
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    Normal and lognormal data distribution in geochemistry: death of a myth. Consequences for the statistical treatment of geochemical and environmental data (2000)
    Springer
    Environmental geology 39 (2000), S. 1001-1014 
    Details
    ISSN: 1432-0495
    Keywords: Key words Normal distribution ; Lognormal distribution ; Geochemistry ; Exploratory data ; analysis ; Multivariate normal distribution ; Robust methods ; Non-parametric methods ; Median
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract All variables of several large data sets from regional geochemical and environmental surveys were tested for a normal or lognormal data distribution. As a general rule, almost all variables (up to more than 50 analysed chemical elements per data set) show neither a normal or a lognormal data distribution. Even when different transformation methods are used more than 70 % of all variables in every single data set do not approach a normal distribution. Distributions are usually skewed, have outliers and originate from more than one process. When dealing with regional geochemical or environmental data normal and/or lognormal distributions are an exception and not the rule. This observation has serious consequences for the further statistical treatment of geochemical and environmental data. The most widely used statistical methods are all based on the assumption that the studied data show a normal or lognormal distribution. Neglecting that geochemcial and environmental data show neither a normal or lognormal distribution will lead to biased or faulty results when such techniques are used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002549900081
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  • 16
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    A model for the magmatic–hydrothermal system at Mount Rainier, Washington, from seismic and geochemical observations (2000)
    Springer
    Bulletin of volcanology 61 (2000), S. 425-436 
    Details
    ISSN: 1432-0819
    Keywords: Key words Mount Rainier ; Seismicity ; Geochemistry ; Magmatic–hydrothermal system model ; Volcano monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Mount Rainier is one of the most seismically active volcanoes in the Cascade Range, with an average of one to two high-frequency volcano-tectonic (or VT) earthquakes occurring directly beneath the summit in a given month. Despite this level of seismicity, little is known about its cause. The VT earthquakes occur at a steady rate in several clusters below the inferred base of the Quaternary volcanic edifice. More than half of 18 focal mechanisms determined for these events are normal, and most stress axes deviate significantly from the regional stress field. We argue that these characteristics are most consistent with earthquakes in response to processes associated with circulation of fluids and magmatic gases within and below the base of the edifice.Circulation of these fluids and gases has weakened rock and reduced effective stress to the point that gravity-induced brittle fracture, due to the weight of the overlying edifice, can occur. Results from seismic tomography and rock, water, and gas geochemistry studies support this interpretation. We combine constraints from these studies into a model for the magmatic system that includes a large volume of hot rock (temperatures greater than the brittle–ductile transition) with small pockets of melt and/or hot fluids at depths of 8–18 km below the summit. We infer that fluids and heat from this volume reach the edifice via a narrow conduit, resulting in fumarolic activity at the summit, hydrothermal alteration of the edifice, and seismicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00008909
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  • 17
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    Natural Geological Weighing Lysimeters: Calibration Tools for Satellite and Ground Surface Gravity Monitoring of Subsurface Water-Mass Change (2000)
    Springer
    Natural resources research 9 (2000), S. 147-156 
    Details
    ISSN: 1573-8981
    Keywords: Gravity ; hydrology ; lysimeter ; GRACE ; aquifer ; groundwater ; storage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Increased accuracy in measuring temporal variations in the Earth's gravity field allow inprinciple the use of gravity observations to deduce subsurface water-mass changes. This canbe with respect to a small area, or as a larger spatial average of water mass change usinggravity observations from low-altitude satellites, such as the forthcoming GRACE mission.At both scales, there is a need to validate gravity-based estimates against field recordings ofactual subsurface water-mass variations. In practice, this could prove difficult because thespatial integral of all water-storage change components can be subject to considerable fieldmeasurement error. An alternative approach to the validation process is proposed by whichsuitable geological formations are utilized as giant weighing devices to directly measure area-integratedwater-mass changes. The existence of such “natural geological weighing lysimeters”is demonstrated using observations from a replicated experimental site in New Zealand. Sitesof this type could be used to verify water-storage change estimates derived from sensitiveground surface gravity instrumentation. In addition, geological lysimeters could be used tomake local checks on the accuracy of any estimated regional water-mass time series, whichis proposed for satellite calibration. The land area “weighed” by a geological lysimeter increaseswith formation depth and it is speculated that recordings made at oil well depth may allowdirect monitoring of subsurface water mass changes at the regional scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010147527484
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  • 18
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    The Western Boundary of the Equatorial Pacific Upwelling: Some Consequences of Climatic Variability on Hydrological and Planktonic Properties (2000)
    Springer
    Journal of oceanography 56 (2000), S. 463-471 
    Details
    ISSN: 1573-868X
    Keywords: Equatorial Pacific ; upwelling western boundary ; climatic variability ; hydrology ; plankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The longitude of the western limit of the equatorial Pacific upwelling is a key parameter for studies of carbon budget and pelagic fisheries variability. Although it is well defined at the surface on the equator by a salinity front and a sharp variation of the partial pressure of CO2, data from two equatorial cruises make it clear that this hydrological limit does not necessarily coincide with the boundary of the nitrate and chlorophyll enriched area. In January-February 1991 during a non-El Niño period, when trade winds and the South Equatorial current (SEC) were favorable to upwelling, the two limits were at the same longitude. Conversely, in September-October 1994 during El Niño conditions, when the equatorial upwelling had stopped, the nitrate and chlorophyll enriched zone was found a few degrees of longitude east of the hydrological boundary (5.5° at the surface and 2.5° for the 50 m upper layer), whereas no such offset was observed for zooplankton biomass. A simple model, based on the HNLC (High Nutrient - Low Chlorophyll) ecosystem functioning, was initialized with nitrate uptake measurements and estimates of upwelling break duration. The model results support the hypothesis that zonal separation of the limits arises from biological processes (i.e. nitrate uptake and phytoplankton grazing) achieved during that upwelling break.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011136608053
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  • 19
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    Electronic Resource
    Nutrient losses in runoff from grasslandand shrubland habitats in southern New Mexico: II. Field plots (2000)
    Springer
    Biogeochemistry 49 (2000), S. 69-86 
    Details
    ISSN: 1573-515X
    Keywords: Bouteloua eriopoda ; Chihuahuan Desert ; desertification ; hydrology ; Larrea tridentata ; nitrogen ; nutrient budgets ; phosphorus ; runoff
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Losses of dissolved nutrients (N, P, K, Ca, Mg, Na,Cl, and SO4) in runoff were measured on grasslandand shrubland plots in the Chihuahuan desert ofsouthern New Mexico. Runoff began at a lowerthreshold of rainfall in shrublands than ingrasslands, and the runoff coefficient averaged 18.6%in shrubland plots over a 7-year period. In contrast,grassland plots lost 5.0 to 6.3% of incidentprecipitation in runoff during a 5.5-year period. Nutrient losses from shrubland plots were greater thanfrom grassland plots, with nitrogen losses averaging0.33 kg ha−1 yr−1 vs0.15 kg ha−1 yr−1, respectively, during a 3-year period. Thegreater nutrient losses in shrublands were due tohigher runoff, rather than higher nutrientconcentrations in runoff. In spite of these nutrientlosses in runoff, all plots showed net accumulationsof most elements due to inputs from atmosphericdeposition. Therefore, loss of soil nutrients byhillslope runoff cannot, by itself, account for thedepletion of soil fertility associated withdesertification in the Chihuahuan desert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006246126915
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  • 20
    Electronic Resource
    Electronic Resource
    Nitrogen solutes in an Adirondack forested watershed: Importance of dissolved organic nitrogen (2000)
    Springer
    Biogeochemistry 48 (2000), S. 165-184 
    Details
    ISSN: 1573-515X
    Keywords: Adirondack Mountains ; total organic nitrogen ; hydrology ; nitrogen retention ; nitrogen saturation ; watershed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nitrogen (N) dynamics were evaluated from 1 June 1995 through 31 May 1996 within the Arbutus Lake watershed in the Adirondack Mountains of New York State, USA. At the Arbutus Lake outlet dissolved organic nitrogen (DON), NO3 - and NH4 + contributed 61%, 33%, and 6% respectively, to the total dissolved nitrogen (TDN) flux (259 mol ha-1 yr-1). At the lake inlet DON, NO3 -, and NH4 - constituted 36%, 61%, and 3% respectively, of TDN flux (349 mol ha-1 yr-1). Differences between the factors that control DON, NO3 +, and NH4 + stream water concentrations were evaluated using two methods for estimating annual N flux at the lake inlet. Using biweekly sampling NO3 - and NH4 + flux was 10 and 4 mol ha-1 yr-1 respectively, less than flux estimates using biweekly plus storm and snowmelt sampling. DON flux was 18 mol ha-1 yr-1 greater using only biweekly sampling. These differences are probably not of ecological significance relative to the total flux of N from the watershed (349 mol ha-1 yr-1). Dissolved organic N concentrations were positively related to discharge during both the dormant (R2 = 0.31; P 〈 0.01) and growing season (R2 = 0.09; P 〈 0.01). There was no significant relationship between NO3 - concentration and discharge during the dormant season, but a significant negative relationship was found during the growing season (R2 = 0.29; P 〈 0.01). Biotic controls in the growing season appeared to have had a larger impact on stream water NO3 - concentrations than on DON concentrations. Arbutus Lake had a major impact on stream water N concentrations of the four landscape positions sampled, suggesting the need to quantify within lake processes to interpret N solute losses and patterns in watershed-lake systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006121828108
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