Mercury-binding proteins in the slipper limpet,Crepidula fornicata,exposed to increased soluble mercury     

Florence L. Harrison  Kathleen Watness  David A. Nelson  James E. Miller  Anthony Calabrese 《Estuaries and Coasts》1987,10(1):78-83

Crepidula fornicata were held in a flow-through bioassay system and exposed to sand-filtered seawater to which no soluble mercury (control) was added or to which either 5, 25, or 50 μg 1^?1 soluble Hg was added. At specific intervals during the 16-week experiment, a group of limpets was removed from each tank; one subgroup was exposed for 48 h to high concentrations of Hg, and another was analyzed for Hg-binding proteins by gelpermeation chromatography and spectrometry. Mortality from exposure to Hg in the 48-h acute toxicity tests was related to concentrations of Hg experienced both during the long-term exposure period and the 48-h exposure period. Chronic exposure to low levels of Hg resulted in increased amounts of total Hg in the whole body and in the low-molecular-weight Hg-binding proteins. No evidence was found for increased tolerance to Hg with preexposure.  相似文献   

Stochastic analysis of estuarine hydraulics     

R. Willis  B. A. Finney  M. McKee  A. Militello 《Stochastic Environmental Research and Risk Assessment (SERRA)》1989,3(2):71-84

A new methodology is presented for the solution of the stochastic hydraulic equations characterizing steady, one-dimensional estuarine flow. The methodology is predicated on quasi-linearization, perturbation methods, and the finite difference approximation of the stochastic differential operators. Assuming Manning's roughness coefficient is the principal source of uncertainty in the model, stochastic equations are presented for the water depths and flow rates in the estuarine system. Moment equations are developed for the mean and variance of the water depths. The moment equations are compared with the results of Monte Carlo simulation experiments. The results confirm that for any spatial location in the estuary that (1) as the uncertainty in the channel roughness increases, the uncertainty in mean depth increases, and (2) the predicted mean depth will decrease with increasing uncertainty in Manning'sn. The quasi-analytical approach requires significantly less computer time than Monte Carlo simulations and provides explicit  相似文献   

The use of²³⁴Th/²³⁸ disequilibrium to examine the fate of particle-reactive species on the Yangtze continental shelf     

Brent A. McKee  David J. DeMaster  Charles A. Nittrouer 《Earth and Planetary Science Letters》1984,68(3):431-442

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Isotopic composition of surface-correlated chromium in Apollo 16 lunar soils     

B.Kathleen Kitts  Frank A. Podosek  Joyce C. Brannon  Randy L. Korotev 《Geochimica et cosmochimica acta》2003,67(24):4881-4893

We have analyzed by thermal ionization mass spectrometry (TIMS) the isotopic composition of Cr in five progressive etches of size-sorted plagioclase grains separated from lunar soils 60601 and 62281. Aliquots of the etch solutions were spiked for isotopic dilution (ID) analysis of Cr and Ca. The Ca ID data indicate that the initial etch steps represent dissolution of an average 0.1 to 0.2 μm depth from the grain surfaces, the approximate depth expected for implanted solar wind. The Cr/Ca ratio in the initial etches is several fold higher than that expected for bulk plagioclase composition, but in subsequent etches decreases to approach the bulk value. This indicates a source of Cr extrinsic to the plagioclase grains, surface-correlated and resident in the outermost fraction of a μm, which we provisionally identify as solar wind Cr. The surface-correlated Cr is isotopically anomalous and by conventional TIMS data reduction has approximately 1 permil excess ⁵⁴Cr and half as great excess ⁵³Cr. In successive etches, as the Cr/Ca ratio decreases and approaches the bulk plagioclase value, the magnitude of the apparent anomalies decreases approaching normal composition. If these results do indeed characterize the solar wind, then either the solar wind is enriched in Cr due to spallation in the solar atmosphere, or the Earth and the various parent bodies of the meteorites are isotopically distinct from the Sun and must have formed from slightly different mixes of presolar materials. Alternative interpretations include the possibility that the anomalous Cr is meteoritic rather than solar or that the observed (solar) Cr is normal except for a small admixture of spallation Cr generated on the Moon. We consider these latter possibilities less likely than the solar wind interpretation. However, they cannot be eliminated and remain working hypotheses.  相似文献   

Strontium Isotopic Signatures of the Streams and Lakes of Taylor Valley, Southern Victoria Land, Antarctica: Chemical Weathering in a Polar Climate     

W. B. Lyons  Carmen A. Nezat  Larry V. Benson  Thomas D. Bullen  Elizabeth Y. Graham  Jesicca Kidd  Kathleen A. Welch  James M. Thomas 《Aquatic Geochemistry》2002,8(2):75-95

We have collected and analyzed a series of water samples from three closed-basin lakes (Lakes Bonney, Fryxell, and Hoare) in Taylor Valley, Antarctica, and the streams that flow into them. In all three lakes, the hypolimnetic waters have different ⁸⁷Sr/⁸⁶Sr ratios than the surface waters, with the deep water of Lakes Fryxell and Hoare being less radiogenic than the surface waters. The opposite occurs in Lake Bonney. The Lake Fryxell isotopic ratios are lower than modern-day ocean water and most of the whole-rock ratios of the surrounding geologic materials. A conceivable source of Sr to the system could be either the Cenozoic volcanic rocks that make up a small portion of the till deposited in the valley during the Last Glacial Maximum or from marble derived from the local basement rocks. The more radiogenic ratios from Lake Bonney originate from ancient salt deposits that flow into the lake from Taylor Glacier and the weathering of minerals with more radiogenic Sr isotopic ratios within the tills. The Sr isotopic data from the streams and lakes of Taylor Valley strongly support the notion documented by previous investigators that chemical weathering has been, and is currently, a major process in determining the overall aquatic chemistry of these lakes in this polar desert environment.  相似文献   

New records of Ediacaran Acraman ejecta in drillholes from the Stuart Shelf and Officer Basin,South Australia     

Andrew C. Hill  Peter W. Haines  Kathleen Grey  Sebastian Willman 《Meteoritics & planetary science》2007,42(11):1883-1891

Abstract— New occurrences of the Acraman impact ejecta layer were recently discovered in two South Australian drillholes, SCYW‐79 1a (Stuart Shelf) and Munta 1 (Officer Basin) using lithostratigraphy, acritarch biostratigraphy, carbon isotope stratigraphy, and biomarker anomalies to predict the stratigraphic position. The ejecta layer is conspicuous because it consists of pink, sandsized, angular fragments of volcanic rock distributed along the bedding plane surface of green marine siltstone. In SCYW‐79 1a it forms a layer 5 mm thick; in Munta 1 the ejecta layer is thin and discontinuous because of its distance (?550 km) from the impact structure. Palynological, biomarker, and carbon isotope anomalies can now be shown to coincide with the ejecta layer in SCYW‐79 1a and Munta 1 suggesting the Acraman impact event may have had far reaching influences on the rapidly evolving Ediacaran biological and geochemical cycles.  相似文献   

Metrics for the comparative analysis of geospatial datasets with applications to high-resolution grid-based population data     

Aarthy Sabesan  Kathleen Abercrombie  Auroop R. Ganguly  Budhendra Bhaduri  Eddie A. Bright  Phillip R. Coleman 《GeoJournal》2007,69(1-2):81-91

Geospatial data sciences have emerged as critical requirements for high-priority application solutions in diverse areas, including, but not limited to, the mitigation of natural and man-made disasters. Three sets of metrics, adopted or customized from geo-statistics, applied meteorology and signal processing, are tested in terms of their ability to evaluate geospatial datasets, specifically two population databases commonly used for disaster preparedness and consequence management. The two high-resolution, grid-based population datasets are the following: The LandScan dataset available from the Geographic Information Science and Technology (GIST) group at the Oak Ridge National Laboratory (ORNL), and the Gridded Population of the World (GPW) dataset available from the Center for International Earth Science Information Network (CIESIN) group at Columbia University. Case studies evaluate population data across the globe, specifically, the metropolitan areas of Washington DC, USA, Los-Angeles, USA, and Houston, USA, and London, UK, as well as the country of Iran. The geospatial metrics confirm that the two population datasets have significant differences, especially in the context of their utility for disaster readiness and mitigation. While this paper primarily focuses on grid based population datasets and disaster management applications, the sets of metrics developed here can be generalized to other geospatial datasets and applications. Future research needs to develop metrics for geospatial and temporal risks and associated uncertainties in the context of disaster management. The U. S. Government’s right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.  相似文献   

Aspects of Proterozoic stromatolite biostratigraphy in Western Australia     

Kathleen Grey 《Precambrian Research》1982,18(4):347-365

Stromatolites are abundant at many horizons in the Proterozoic of Western Australia. Recent advances in knowledge of Proterozoic stratigraphy of the state have provided a more detailed framework for interpreting the stromatolite data than has been available previously. In the 1.7 Ga Earaheedy Group of the Nabberu Basin a characteristic stromatolite assemblage occurs, and within the basin a biostratigraphic succession can be recognized. The assemblage contains several new forms which belong to new groups. The need to erect new groups for these early Proterozoic stromatolites is in agreement with recent studies in Canada, northern Europe and South Africa, and suggests that the problem of ‘younger’ or late Proterozoic stromatolite groups in early Proterozoic rocks mentioned by previous workers is a result of a lack of rigour in defining taxa. Examination of type material is necessary to determine how closely the Earaheedy forms resemble those described from these other regions.In Western Australia some stromatolite forms have a restricted vertical range and similar taxa occur in beds of approximately the same age in widely-separated areas: e.g. Kimberley Group and Earaheedy Group; Scorpion Group and Limbunya, Birrindudu, McArthur, Mt. Rigg and Mt. Albert Groups and Bungle Bungle Dolomite; Tolmer and Bullita Groups; Moora and Bangemall Groups; Kai Ki Beds, Louisa Downs, Mount House and Albert Edward Groups.Stromatolite diversity shows a decline in the number of taxa at about 1.1. Ga in the Bangemall Group. More data are required to determine whether this decline is universal or specific to the Bangemall Group. This study indicates that a stromatolite biostratigraphy for Western Australia is feasible and is consistent with data from other parts of Australia. Thus emphasis on correlation should be placed on the stromatolite form rather than the group, and intercontinental correlations should be attempted only when local biostratigraphic schemes have been firmly established.  相似文献   

Observations of vertical atmospheric structure in a deep mountain valley     

C. David Whiteman  Dr. Thomas B. McKee 《Meteorology and Atmospheric Physics》1977,26(1):39-50

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Oxyanion Concentrations in Eastern Sierra Nevada Rivers – 3. Boron, Molybdenum, Vanadium, and Tungsten     

Kevin H. Johannesson  W. Berry Lyons  Elizabeth Y. Graham  Kathleen A. Welch 《Aquatic Geochemistry》2000,6(1):19-46

Water samples were collected from 10 locations along the Truckee River system, 14 locations along the Walker River system, and 12 locations along the Carson River, and analyzed for B, Mo, V, W, Na, Cl, and pH. Boron concentrations ranged from approximately 2 mol/kg in the upper reaches of the Truckee River to almost 1,200 mol/kg in Pyramid Lake. Molybdenum, V, and W had concentrations in the nanomolal range; Mo varied from a low of about 12 nmol/kg to a high of 3,200 nmol/kg (Walker Lake); V ranged from 9 nmol/kg to approximately 470 nmol/kg; and W varied from a low value around 0.8 nmol/kg (West Walker River) to 1,030 nmol/kg. The high concentrations of these oxyanion-forming trace elements in the rivers reflects (1) the relative stability of these oxyanions (e.g., MoO₄ ^2-, HVO₄ ^2-, WO₄ ^2-, B(OH)₃, and/or B(OH)₄ ^-) in the alkaline, well oxygenated river and lake waters, (2) contributions of hydrothermal waters (especially for B), and (3) weathering of rocks/regolith with high concentrations of these elements. In the case of Mo, V, and W, each exhibited relatively conservative behavior in the upper, oxygenated reaches of all three rivers. During the study period the region experienced a prolonged drought such that the lower reaches of each river were typified by no flow or stagnant waters and probably low oxygen and/or anoxic conditions (although not measured). Reductive processes occurring in the low flow to stagnant reaches of each river could have led to removal of Mo, V, and W from solution as coprecipitates with Fe monosulfides, or via sorption to Fe oxides/oxyhydroxides and/or organic matter. Boron, however, exhibited essentially no or minor removal from these rivers, and instead was added to each river via B-rich hydrothermal waters (e.g., Steamboat Creek from Steamboat Hot Springs), or by B-rich groundwaters via base-flow during the extensive drought.  相似文献