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Articles 1 - 30 of 68
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Responses Of Pond-Breeding Amphibians To Wildfire: Short-Term Patterns In Occupancy And Colonization, Blake R. Hossack, Paul Stephen Corn
Responses Of Pond-Breeding Amphibians To Wildfire: Short-Term Patterns In Occupancy And Colonization, Blake R. Hossack, Paul Stephen Corn
United States Geological Survey: Staff Publications
Wildland fires are expected to become more frequent and severe in many ecosystems, potentially posing a threat to many sensitive species. We evaluated the effects of a large, stand-replacement wildfire on three species of pond-breeding amphibians by estimating changes in occupancy of breeding sites during the three years before and after the fire burned 42 of 83 previously surveyed wetlands. Annual occupancy and colonization for each species was estimated using recently developed models that incorporate detection probabilities to provide unbiased parameter estimates. We did not find negative effects of the fire on the occupancy or colonization rates of the long-toed …
Fate Of Fish Production In A Seasonally Flooded Saltmarsh, Philip W. Stevens, Clay L. Montague, Kenneth J. Sulak
Fate Of Fish Production In A Seasonally Flooded Saltmarsh, Philip W. Stevens, Clay L. Montague, Kenneth J. Sulak
United States Geological Survey: Staff Publications
Although saltmarshes are thought to enhance the productivity of open estuarine water, the mechanism by which energy transfer occurs has been debated for decades. One possible mechanism is the transfer of saltmarsh production to estuarine waters by vagile fishes and invertebrates. Monthly estimates of fish standing stock, net fish ingress, and predation were used to develop a bio-mass budget to estimates annual production of fishes and the relative yield to predatory fish, birds, and direct migration to the estuary. Annual production of saltmarsh fishes was estimated to 31.0 gm-2 saltmarsh, which falls within the range of previously reported values …
The Legacy Of Leaded Gasoline In Bottom Sediment Of Small Rural Reservoirs, Kyle E. Juracek, Andrew C. Ziegler
The Legacy Of Leaded Gasoline In Bottom Sediment Of Small Rural Reservoirs, Kyle E. Juracek, Andrew C. Ziegler
United States Geological Survey: Staff Publications
The historical and ongoing lead (Pb) contamination caused by the 20th-century use of leaded gasoline was investigated by an analysis of bottom sediment in eight small rural reservoirs in eastern Kansas, USA. For the reservoirs that were completed before or during the period of maximum Pb emissions from vehicles (i.e., the 1940s through the early 1980s) and that had a major highway in the basin, increased Pb concentrations reflected the pattern of historical leaded gasoline use. For at least some of these reservoirs, residual Pb is still being delivered from the basins. There was no evidence of increased Pb deposition …
Deep-Water Antipatharians: Proxies Of Environmental Change, B. Williams, M.J. Risk, S.W. Ross, K.J. Sulak
Deep-Water Antipatharians: Proxies Of Environmental Change, B. Williams, M.J. Risk, S.W. Ross, K.J. Sulak
United States Geological Survey: Staff Publications
Deep-water (307–697 m) antipatharian (black coral) specimens were collected from the southeastern continental slope of the United States and the north-central Gulf of Mexico. The sclerochronology of the specimens indicates that skeletal growth takes place by formation of concentric coeval layers. We used 210Pb to estimate radial growth rate of two specimens, and to establish that they were several centuries old. Bands were delaminated in KOH and analyzed for carbon and nitrogen stable isotopes. Carbon values ranged from _16.4‰ to _15.7‰; the oldest specimen displayed the largest range in values. Nitrogen values ranged from 7.7‰ to 8.6‰. …
Anguilliform Larvae Collected Off North Carolina, Steve W. Ross, Tara L. Casazza, Andrea M. Quattrini, Kenneth J. Sulak
Anguilliform Larvae Collected Off North Carolina, Steve W. Ross, Tara L. Casazza, Andrea M. Quattrini, Kenneth J. Sulak
United States Geological Survey: Staff Publications
The distinctive larval stage of eels (leptocephalus) facilitates dispersal through prolonged life in the open ocean. Leptocephali are abundant and diverse off North Carolina, yet data on distributions and biology are lacking. The water column (from surface to 1,293 m) was sampled in or near the Gulf Stream off Cape Hatteras, Cape Lookout, and Cape Fear, North Carolina during summer through fall of 1999–2005, and leptocephali were collected by neuston net, plankton net, Tucker trawl, and dip net. Additional samples were collected nearly monthly from a transect across southern Onslow Bay, North Carolina (from surface to 91 m) from April …
Sprawl And The Resilience Of Humans And Nature: An Introduction To The Special Feature, Craig R. Allen
Sprawl And The Resilience Of Humans And Nature: An Introduction To The Special Feature, Craig R. Allen
United States Geological Survey: Staff Publications
Human-driven change in land use and land cover is an accelerating global phenomenon with far-reaching implications for food production, forest and water resources, the climate, and biogeochemical cycles (Foley et al. 2005). It affects the amount and configuration of habitat available for animals ranging from soil nematodes to elephants. It affects the provision of ecological goods and services for human beings. It affects the processes and function of ecosystems.
Discontinuities In Ecological Data, Craig R. Allen
Discontinuities In Ecological Data, Craig R. Allen
United States Geological Survey: Staff Publications
Historically, ecology has focused on continuous distributions and smooth transitions. Only recently have discontinuities and thresholds become an explicit focus in some areas of ecology, especially in the realm of complex systems. The study of animal body mass distributions has been recognized for its potential to provide insight into the underlying processes shaping animal communities. Hutchinson (1) formalized the understanding of species niches and the potential for competition to shape body mass distributions. However, despite a long history of theoretical and empirical pursuit, the mechanisms driving patterns in body mass distributions remain poorly understood. The work of Scheffer and van …
Widespread Presence Of Naturally Occurring Perchlorate In High Plains Of Texas And New Mexico, Srinath Rajagopalan, Todd Anderson, Lynne Fahlquist, Ken Rainwater, Moira Ridley, W. Andrew Jackson
Widespread Presence Of Naturally Occurring Perchlorate In High Plains Of Texas And New Mexico, Srinath Rajagopalan, Todd Anderson, Lynne Fahlquist, Ken Rainwater, Moira Ridley, W. Andrew Jackson
United States Geological Survey: Staff Publications
Perchlorate (ClO4-) occurrence in groundwater has previously been linked to industrial releases and the historic use of Chilean nitrate fertilizers. However, recently a number of occurrences have been identified for which there is no obvious anthropogenic source. Groundwater from an area of 155 000 km2 in 56 counties in northwest Texas and eastern New Mexico is impacted by the presence of ClO4-. Concentrations were generally low (<4 ppb), although some areas are impacted by concentrations up to 200 ppb. ClO4- distribution is not related to well type (public water system, domestic, agricultural, or water-table monitoring) or aquifer (Ogallala, Edward Trinity High Plains, Edwards Trinity …
Change In Atmospheric Mineral Aerosols In Response To Climate: Last Glacial Period, Preindustrial, Modern, And Doubled Carbon Dioxide Climates, Natalie M. Mahowald, Daniel R. Muhs, Samuel Levis, Philip J. Rasch, Masaru Yoshioka, Charles S. Zender, Chao Luo
Change In Atmospheric Mineral Aerosols In Response To Climate: Last Glacial Period, Preindustrial, Modern, And Doubled Carbon Dioxide Climates, Natalie M. Mahowald, Daniel R. Muhs, Samuel Levis, Philip J. Rasch, Masaru Yoshioka, Charles S. Zender, Chao Luo
United States Geological Survey: Staff Publications
Desert dust simulations generated by the National Center for Atmospheric Research’s Community Climate System Model for the current climate are shown to be consistent with present day satellite and deposition data. The response of the dust cycle to last glacial maximum, preindustrial, modern, and doubled-carbon dioxide climates is analyzed. Only natural (non-land use related) dust sources are included in this simulation.
Multi-Species Patterns Of Avian Cholera Mortality In Nebraska’S Rainwater Basin, Julie A. Blanchong, Michael D. Samuel, Gene Mack
Multi-Species Patterns Of Avian Cholera Mortality In Nebraska’S Rainwater Basin, Julie A. Blanchong, Michael D. Samuel, Gene Mack
United States Geological Survey: Staff Publications
Nebraska’s Rainwater Basin (RWB) is a key spring migration area for millions of waterfowl and other avian species. Avian cholera has been endemic in the RWB since the 1970s and in some years tens of thousands of waterfowl have died from the disease. We evaluated patterns of avian cholera mortality in waterfowl species using the RWB during the last quarter of the 20th century. Mortality patterns changed between the years before (1976–1988) and coincident with (1989–1999) the dramatic increases in lesser snow goose abundance and mortality. Lesser snow geese (Chen caerulescens caerulescens) have commonly been associated with mortality …
A Cool Eastern Pacific Ocean At The Close Of The Last Interglacial Complex, Daniel R. Muhs, Kathleen R. Simmons, George L. Kennedy, Kenneth R. Ludwig, Lindsey T. Groves
A Cool Eastern Pacific Ocean At The Close Of The Last Interglacial Complex, Daniel R. Muhs, Kathleen R. Simmons, George L. Kennedy, Kenneth R. Ludwig, Lindsey T. Groves
United States Geological Survey: Staff Publications
New high-precision thermal ionization mass-spectrometric (TIMS) U-series ages of solitary corals (Balanophyllia elegans) from several marine terrace localities along the California and southern Oregon coasts date to the ~80,000 yr BP high stand of sea, correlative with marine isotope substage 5a, late in the last interglacial complex. Ages of multiple corals from localities north of Point Año Nuevo (central California) and San Nicolas Island (southern California) suggest that this high sea stand could have lasted at least 8000 yr, from ~84,000 to ~76,000 yr BP. These ages overlap with those from marine deposits on tectonically stable Bermuda and …
Paleoclimatic Evidence For Future Ice-Sheet Instability And Rapid Sea-Level Rise, Jonathan T. Overpeck, Bette L. Otto-Bliesner, Gifford H. Miller, Daniel R. Muhs, Richard B. Alley, Jeffrey T. Kiehl
Paleoclimatic Evidence For Future Ice-Sheet Instability And Rapid Sea-Level Rise, Jonathan T. Overpeck, Bette L. Otto-Bliesner, Gifford H. Miller, Daniel R. Muhs, Richard B. Alley, Jeffrey T. Kiehl
United States Geological Survey: Staff Publications
Sea-level rise from melting of polar ice sheets is one of the largest potential threats of future climate change. Polar warming by the year 2100 may reach levels similar to those of 130,000 to 127,000 years ago that were associated with sea levels several meters above modern levels; both the Greenland Ice Sheet and portions of the Antarctic Ice Sheet may be vulnerable. The record of past ice-sheet melting indicates that the rate of future melting and related sea-level rise could be faster than widely thought.
Ice Sheets And Sea Level, Johannes Oerlemans, Dorthe Dahl-Jensen, Valérie Masson-Delmotte, Jonathan T. Overpeck, Bette L. Otto-Bliesner, Gifford H. Miller, Richard B. Alley, Daniel R. Muhs, Shawn J. Marshall
Ice Sheets And Sea Level, Johannes Oerlemans, Dorthe Dahl-Jensen, Valérie Masson-Delmotte, Jonathan T. Overpeck, Bette L. Otto-Bliesner, Gifford H. Miller, Richard B. Alley, Daniel R. Muhs, Shawn J. Marshall
United States Geological Survey: Staff Publications
The estimate of the contribution of the Greenland Ice Sheet (GIS) to the higher sea level stand in the Eemian interglacial (between 2.2 and 3.4 m) is based on the assumption that there was no ice at the location of the Dye-3 ice core in southern Greenland. However, Eemian ice has been found at the base of this ice core. The presence of Eemian ice in south and coastal Greenland implies that the GIS was essentially intact in a much warmer climate and could not have contributed more than 1 to 2 m to sea-level rise.
Acoustic Stratigraphy Of Bear Lake, Utah–Idaho—Late Quaternary Sedimentation Patterns In A Simple Half-Graben, Steven M. Colman
Acoustic Stratigraphy Of Bear Lake, Utah–Idaho—Late Quaternary Sedimentation Patterns In A Simple Half-Graben, Steven M. Colman
United States Geological Survey: Staff Publications
A277-km network of high-resolution seismic-reflection profiles, supplemented with a sidescan-sonar mosaic of the lake floor, was collected in Bear Lake, Utah–Idaho, in order to explore the sedimentary framework of the lake’s paleoclimate record. The acoustic stratigraphy is tied to a 120 m deep, continuously cored drill hole in the lake. Based on the age model for the drill core, the oldest continuously mapped acoustic reflector in the data set has an age of about 100 ka, although older sediments were locally imaged.
The acoustic stratigraphy of the sediments below the lake indicates that the basin developed primarily as a simple …
The Geochemical Record Of The Last 17,000 Years In The Guaymas Basin, Gulf Of California, Walter E. Dean
The Geochemical Record Of The Last 17,000 Years In The Guaymas Basin, Gulf Of California, Walter E. Dean
United States Geological Survey: Staff Publications
Sediments deposited on the western slope of the Guaymas Basin in the central Gulf of California are composed predominantly of detrital clastic material and biogenic silica (biopal), with minor organic material (average of 2.8% organic carbon) and calcium carbonate. The CaCO3 is derived from calcareous plankton and is highly variable ranging from 0% to 16%. In general, the CaCO3 content of the sediments varies inversely with the biopal content, reflecting the relative abundance of calcareous and siliceous plankton in the photic zone. Siliceous plankton dominate when winds are predominantly out of the northwest producing strong upwelling. Calcareous plankton …
Abundance And Distribution Of Selected Elements In Soils, Stream Sediments, And Selected Forage Plants From Desert Tortoise Habitats In The Mojave And Colorado Deserts, Usa, M. A. Chaffee, K. H. Berry
Abundance And Distribution Of Selected Elements In Soils, Stream Sediments, And Selected Forage Plants From Desert Tortoise Habitats In The Mojave And Colorado Deserts, Usa, M. A. Chaffee, K. H. Berry
United States Geological Survey: Staff Publications
A baseline and background chemical survey was conducted in southeastern California, USA, to identify potential sources of toxicants in natural and anthropogenically-altered habitats of the threatened desert tortoise (Gopherus agassizii). Soil, stream sediment, and plant samples were collected from six tortoise habitat study areas in the Mojave and Colorado deserts and analysed for up to 66 different elements. The chemical analyses provided new information on the abundances and distributions of selected elements in this region. Soil, stream-sediment, and plant analyses showed distinct variations in bulk chemistries from locality to locality. Variations were, in general, consistent with the many …
Mineralogical Characterization Of Protolith And Fault Rocks From The Safod Main Hole, John G. Solum, Stephen H. Hickman, David A. Lockner, Diane E. Moore, Ben A. Van Der Pluijm, James P. Evans
Mineralogical Characterization Of Protolith And Fault Rocks From The Safod Main Hole, John G. Solum, Stephen H. Hickman, David A. Lockner, Diane E. Moore, Ben A. Van Der Pluijm, James P. Evans
United States Geological Survey: Staff Publications
Washed cuttings provide a continuous record of the rocks encountered during drilling of the main hole of the San Andreas Fault Observatory at Depth (SAFOD). Both protolith and fault rocks exhibit a wide variety of mineral assemblages that reflect variations in some combination of lithology, P-T conditions, deformation mechanisms, and fluid composition and abundance. Regions of distinct neomineralization bounded by faults may record alteration associated with fluid reservoirs confined by faults. In addition, both smectites occurring as mixed-layer phases and serpentine minerals are found in association with active strands of the San Andreas Fault that were intersected during drilling, although …
Measuring Groundwater–Surface Water Interaction And Its Effect On Wetland Stream Benthic Productivity, Trout Lake Watershed, Northern Wisconsin, Usa, Randall J. Hunt, Mac Strand, John F. Walker
Measuring Groundwater–Surface Water Interaction And Its Effect On Wetland Stream Benthic Productivity, Trout Lake Watershed, Northern Wisconsin, Usa, Randall J. Hunt, Mac Strand, John F. Walker
United States Geological Survey: Staff Publications
Measurements of groundwater–surface water exchange at three wetland stream sites were related to patterns in benthic productivity as part of the US Geological Survey’s Northern Temperate Lakes–Water, Energy and Biogeochemical Budgets (NTL–WEBB) project. The three sites included one high groundwater discharge (HGD) site, one weak groundwater discharge (WGD) site, and one groundwater recharge (GR) site. Large upward vertical gradients at the HGD site were associated with smallest variation in head below the stream and fewest gradient reversals between the stream and the groundwater beneath the stream, and the stream and the adjacent streambank. The WGD site had the highest number …
Comparison Of Breeding Bird And Vegetation Communities In Primary And Secondary Forests Of Great Smoky Mountains National Park, Theodore R. Simons, Susan A. Shriner, George L. Farnsworth
Comparison Of Breeding Bird And Vegetation Communities In Primary And Secondary Forests Of Great Smoky Mountains National Park, Theodore R. Simons, Susan A. Shriner, George L. Farnsworth
United States Geological Survey: Staff Publications
We compared breeding bird communities and vegetation characteristics at paired point locations in primary (undisturbed) and mature secondary forest (70–100 years old) sites in Great Smoky Mountains National Park, USA to understand how sites logged prior to creation of the park compare to undisturbed sites following 70 years of protection from human disturbance. We found that bird and vegetation communities are currently similar, but retain some differences in species composition. Rank abundance curves for primary and secondary forest bird communities showed very similar patterns of species dominance. Species composition was also similar on the two sites which shared 24 of …
River-Aquifer Interactions, Geologic Heterogeneity, And Low-Flow Management, Jan H. Fleckenstein, Richard G. Niswonger, Graham E. Fogg
River-Aquifer Interactions, Geologic Heterogeneity, And Low-Flow Management, Jan H. Fleckenstein, Richard G. Niswonger, Graham E. Fogg
United States Geological Survey: Staff Publications
Low river flows are commonly controlled by river-aquifer exchange, the magnitude of which is governed by hydraulic properties of both aquifer and aquitard materials beneath the river. Low flows are often important ecologically. Numerical simulations were used to assess how textural heterogeneity of an alluvial system influences river seepage and low flows. The Cosumnes River in California was used as a test case. Declining fall flows in the Cosumnes River have threatened Chinook salmon runs. A ground water–surface water model for the lower river basin was developed, which incorporates detailed geostatistical simulations of aquifer heterogeneity. Six different realizations of heterogeneity …
The Role Of Ground Water In Generating Streamflow In Headwater Areas And In Maintaining Base Flow, Thomas C. Winter
The Role Of Ground Water In Generating Streamflow In Headwater Areas And In Maintaining Base Flow, Thomas C. Winter
United States Geological Survey: Staff Publications
The volume and sustainability of streamflow from headwaters to downstream reaches commonly depend on contributions from ground water. Streams that begin in extensive aquifers generally have a stable point of origin and substantial discharge in their headwaters. In contrast, streams that begin as discharge from rocks or sediments having low permeability have a point of origin that moves up and down the channel seasonally, have small incipient discharge, and commonly go dry. Nearly all streams need to have some contribution from ground water in order to provide reliable habitat for aquatic organisms. Natural processes and human activities can have a …
Effects Of Historical Climate Change, Habitat Connectivity, And Vicariance On Genetic Structure And Diversity Across The Range Of The Red Tree Vole (Phenacomys Longicaudus) In The Pacific Northwestern United States, Mark P. Miller, M. Renee Bellinger, Eric D. Forsman, Susan M. Haig
Effects Of Historical Climate Change, Habitat Connectivity, And Vicariance On Genetic Structure And Diversity Across The Range Of The Red Tree Vole (Phenacomys Longicaudus) In The Pacific Northwestern United States, Mark P. Miller, M. Renee Bellinger, Eric D. Forsman, Susan M. Haig
United States Geological Survey: Staff Publications
Phylogeographical analyses conducted in the Pacific Northwestern United States have often revealed concordant patterns of genetic diversity among taxa. These studies demonstrate distinct North/South genetic discontinuities that have been attributed to Pleistocene glaciation. We examined phylogeographical patterns of red tree voles (Phenacomys longicaudus) in western Oregon by analysing mitochondrial control region sequences for 169 individuals from 18 areas across the species’ range. Cytochrome b sequences were also analysed from a subset of our samples to confirm the presence of major haplotype groups. Phylogenetic network analyses suggested the presence of two haplotype groups corresponding to northern and southern regions …
Phylogeography And Spatial Genetic Structure Of The Southern Torrent Salamander: Implications For Conservation And Management, Mark P. Miller, Susan M. Haig, R. Steven Wagner
Phylogeography And Spatial Genetic Structure Of The Southern Torrent Salamander: Implications For Conservation And Management, Mark P. Miller, Susan M. Haig, R. Steven Wagner
United States Geological Survey: Staff Publications
The Southern torrent salamander (Rhyacotriton variegatus) was recently found not warranted for listing under the US Endangered Species Act due to lack of information regarding population fragmentation and gene flow. Found in small-order streams associated with late-successional coniferous forests of the US Pacific Northwest, threats to their persistence include disturbance related to timber harvest activities. We conducted a study of genetic diversity throughout this species’ range to 1) identify major phylogenetic lineages and phylogeographic barriers and 2) elucidate regional patterns of population genetic and spatial phylogeographic structure. Cytochrome b sequence variation was examined for 189 individuals from 72 …
Hybrids And Policy, Susan M. Haig, Fred W. Allendorf
Hybrids And Policy, Susan M. Haig, Fred W. Allendorf
United States Geological Survey: Staff Publications
Hybridization (the interbreeding of individuals from genetically distinct populations, regardless of their taxonomic status) is the double-edged sword of conservation biology. On one hand, increased rates of hybridization because of human activities have led to the extinction of populations and species in plant and animal taxa throughout the world (Rhymer and Simberloff 1996; Allendorf et al. 2001). On the other, hybridization is an important and natural part of the evolutionary process. Thus, hybridization between isolated populations can be an important tool for recovery (Mansfield and Land 2002). However, it has been difficult to develop conservation policies that treat the problems …
Endangered Species Time Line, Leona K. Svancara, J. Michael Scott, Dale D. Goble, Frank W. Davis, Donna Brewer
Endangered Species Time Line, Leona K. Svancara, J. Michael Scott, Dale D. Goble, Frank W. Davis, Donna Brewer
United States Geological Survey: Staff Publications
The Endangered Species Act (ESA) is embedded in a web of statutes designed to regulate relationships between humans and other species that stretch back nearly a millennium (Goble, this volume; Goble and Freyfogle 2002). This chapter presents a time line of federal actions taken to protect wildlife beginning with passage of the Land and Water Conservation Fund Act in 1963 (Act of May 28, 1963). Earlier laws to protect wildlife are discussed elsewhere (Goble, this volume). The time line emphasizes federal actions that conserve species at risk of extinction and significant events in the course of implementing the Endangered Species …
Isotope Sourcing Of Prehistoric Willow And Tule Textiles Recovered From Western Great Basin Rock Shelters And Caves E Proof Of Concept, L.V. Benson, E.M. Hattori, H. E. Taylor, S.R. Poulson, E.A. Jolie
Isotope Sourcing Of Prehistoric Willow And Tule Textiles Recovered From Western Great Basin Rock Shelters And Caves E Proof Of Concept, L.V. Benson, E.M. Hattori, H. E. Taylor, S.R. Poulson, E.A. Jolie
United States Geological Survey: Staff Publications
Isotope and trace-metal analyses were used to determine the origin of plants used to manufacture prehistoric textiles (basketry and matting) from archaeological sites in the western Great Basin. Research focused on strontium (87Sr/86Sr) and oxygen (18O/16O) isotope ratios of willow (Salix sp.) and tule (Schoenoplectus sp.), the dominant raw materials in Great Basin textiles. The oxygen-isotope data indicated that the willow and tule used to produce the textiles were harvested from the banks of rivers or in marshes characterized by flowing water and not from lakes or sinks. The strontium-isotope …
A New Device To Estimate Abundance Of Moist-Soil Plant Seeds, Edward J. Penny, Richard M. Kaminski, Kenneth J. Reinecke
A New Device To Estimate Abundance Of Moist-Soil Plant Seeds, Edward J. Penny, Richard M. Kaminski, Kenneth J. Reinecke
United States Geological Survey: Staff Publications
Methods to sample the abundance of moist-soil seeds efficiently and accurately are critical for evaluating management practices and determining food availability. We adapted a portable, gasoline-powered vacuum to estimate abundance of seeds on the surface of a moist-soil wetland in east-central Mississippi and evaluated the sampler by simulating conditions that researchers and managers may experience when sampling moist-soil areas for seeds. We measured the percent recovery of known masses of seeds by the vacuum sampler in relation to 4 experimentally controlled factors (i.e., seed-size class, sample mass, soil moisture class, and vacuum time) with 2-4 levels per factor. We also …
Sulfur Isotope Geochemistry Of Sulfide Minerals, Robert R. Seal Ii
Sulfur Isotope Geochemistry Of Sulfide Minerals, Robert R. Seal Ii
United States Geological Survey: Staff Publications
Sulfur, the 10th most abundant element in the universe and the 14th most abundant element in the Earth’s crust, is the defining element of sulfide minerals and provides insights into the origins of these minerals through its stable isotopes. The insights come from variations in the isotopic composition of sulfide minerals and related compounds such as sulfate minerals or aqueous sulfur species, caused by preferential partitioning of isotopes among sulfur-bearing phases, known as fractionation. These variations arise from differences in temperature, or more importantly, oxidation and reduction reactions acting upon the sulfur. The oxidation and reduction reactions can occur at …
Simulation Of Solute Movement Through Wellbores To Characterize Public Supply Well Contaminant Vulnerability In The High Plains Aquifer, York, Nebraska, Brian R. Clark, Matthew K. Landon, Leon J. Kauffman, George Z. Hornberger
Simulation Of Solute Movement Through Wellbores To Characterize Public Supply Well Contaminant Vulnerability In The High Plains Aquifer, York, Nebraska, Brian R. Clark, Matthew K. Landon, Leon J. Kauffman, George Z. Hornberger
United States Geological Survey: Staff Publications
A ground-water flow and transport model simulating contaminant movement to public supply wells in the High Plains aquifer near York, Nebraska was developed as part of the U.S. Geological Survey National Water-Quality Assessment Program. Water-quality samples were collected from wells screened in unconfined and confined units. Samples collected from a public supply well and selected monitoring wells completed in the confined aquifer have chemistry and age-tracer concentrations consistent with a mix of young water from unconfined recharge areas combined with relatively older confined aquifer water. These results imply that there are preferential flow paths that permit shallow recharge water and …
Regional Patterns In The Isotopic Composition Of Natural And Anthropogenic Nitrate In Groundwater, High Plains, U.S.A., P. B. Mcmahon, J. K. Bohlke
Regional Patterns In The Isotopic Composition Of Natural And Anthropogenic Nitrate In Groundwater, High Plains, U.S.A., P. B. Mcmahon, J. K. Bohlke
United States Geological Survey: Staff Publications
Mobilization of natural nitrate (NO3-) deposits in the subsoil by irrigation water in arid and semiarid regions has the potential to produce large groundwater NO3- concentrations. The use of isotopes to distinguish between natural and anthropogenic NO3- sources in these settings could be complicated by the wide range in δ15N values of natural NO3-. An ~10 000 year record of paleore-charge from the regionally extensive High Plains aquifer indicates that δ15N values for NO3- derived from natural sources ranged from 1.3 to 12.3‰ and …