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At least 559 records · Page 31Linked to original sources
USGS2013

Mercury bioaccumulation in fishes from subalpine lakes of the Wallowa-Whitman National Forest, northeastern Oregon and western Idaho

Mercury (Hg) is a globally distributed pollutant that poses considerable risks to human and wildlife health. Over the past 150 years since the advent of the industrial revolution, approximately 80 percent of global emissions have come from anthropogenic sources, largely fossil fuel combustion. As a result, atmospheric deposition of Hg has increased by up to 4-fold above pre-industrial times. Because of their isolation, remote high-elevation lakes represent unique environments for evaluating the bioaccumulation of atmospherically deposited Hg through freshwater food webs, as well as for evaluating the relative importance of Hg loading versus landscape influences on Hg bioaccumulation. The increase in Hg deposition to these systems over the past century, coupled with their limited exposure to direct anthropogenic disturbance make them useful indicators for estimating how changes in Hg emissions may propagate to changes in Hg bioaccumulation and ecological risk. In this study, we evaluated Hg concentrations in fishes of high-elevation, sub-alpine lakes in the Wallowa-Whitman National Forest in northeastern Oregon and western Idaho. Our goals were to (1) assess the magnitude of Hg contamination in small-catchment lakes to evaluate the risk of atmospheric Hg to human and wildlife health, (2) quantify the spatial variability in fish Hg concentrations, and (3) determine the ecological, limnological, and landscape factors that are best correlated with fish total mercury (THg) concentrations in these systems. Across the 28 study lakes, mean THg concentrations of resident salmonid fishes varied as much as 18-fold among lakes. Importantly, our top statistical model explained 87 percent of the variability in fish THg concentrations among lakes with four key landscape and limnological variables— catchment conifer density (basal area of conifers within a lake’s catchment), lake surface area, aqueous dissolved sulfate, and dissolved organic carbon. The basal area of conifers within a lake’s catchment was by far the most important variable explaining fish THg concentrations, with an increase in THg concentrations of more than 400 percent across the forest density spectrum. Across all study lakes, fish THg concentrations ranged from 0.004 to 0.438 milligrams per kilogram wet weight (mg/kg ww). Only a single individual fish sample exceeded the U.S. Environmental Protection Agency’s (USEPA) human health tissue residue criteria of 0.3 mg/kg ww. However, 54 percent of fish (N=177) exceeded the more stringent tissue residue criteria (0.04 mg/kg ww) adopted by the Oregon Department of Environmental Quality to better protect subsistence fishers. Additionally, 2 and 10 percent of fish exceeded levels associated with reduced common loon reproduction and behavior, respectively. Whereas 25 and 68 percent of fish sampled exceeded concentrations deemed protective of mink and kingfisher, respectively. These results suggest that THg concentrations may be present in these lakes at levels associated with ecological risk. It is important to note however, that accurate inference on potential impairment cannot be made within the context of this study design and further research is needed to better quantify these risks.

Oregon;Idaho↗
USGS2020

A 450-year record of environmental change from Castle Lake, California (USA), inferred from diatoms and organic geochemistry

A 39-cm sediment core from Castle Lake, California (USA) spans the last ~ 450 years and was analyzed for diatoms and organic geochemistry (δ 15 N, δ 13 C, and C:N), with the goal of determining sensitivity to natural climate variation and twentieth century anthropogenic effects. Castle Lake is a subalpine, nitrogen-limited lake with ~ 5 months of annual ice cover. Human impacts include light recreational use, past fish stocking, and experimental use by the Castle Lake Research Station. The base of the core (below 32 cm; pre mid-1700s) represents the period of maximum ice cover. In contrast, the end of the Little Ice Age (mid 1700s–early 1800s) is dominated by cyclotelloids (mostly Discostella stelligera ), indicating significant open-water periods, a condition that persisted into the early 1900s. Cyclotelloids began to decline in the 1960s and were replaced by the Fragilaria tenera grp. (peak in 1970s), succeeded by Asterionella formosa (peak ~ 2010), and accompanied by a reduction in δ 15 N values and a decrease in C:N that may represent increased atmospheric nitrogen deposition. Another anthropogenic signal was discerned in the core and was interpreted to be the result of an ammonium nitrate fertilization experiment of the epilimnion that was conducted in 1980 and 1981. This signal was manifested in the core largely by a negative excursion in δ 15 N, possibly caused by fractionation during denitrification in surface sediment. A phytoplankton monitoring dataset collected by the Castle Lake Research Station from 1967 to 1984 corroborates the timing of increased araphid euplanktonic species in the 1970s, and increases in two benthic diatoms ( Staurosirella pinnata and Tabellaria fenestrata) , entrained in the phytoplankton tows during the experimentation years. Both ice cover and nitrogen addition appear to be strong drivers that affected the lake diatoms, although additional drivers, such as fish stocking and associated cascade effects need further exploration. These data will be helpful for interpreting longer core records from Castle Lake, should the opportunity arise, as well as cores from similar systems in the region.

California↗
USGS2020

Nutrients and warming interact to force mountain lakes into unprecedented ecological state

While deposition of reactive nitrogen (N) in the 20th century has been strongly linked to changes in diatom assemblages in high-elevation lakes, pronounced and contemporaneous changes in other algal groups suggest additional drivers. We explored the origin and magnitude of changes in two mountain lakes from the end of the Little Ice Age at ca. 1850, to ca. 2010, using lake sediments. We found dramatic changes in algal community abundance and composition. While diatoms remain the most abundant photosynthetic organisms, concentrations of diatom pigments decreased while pigments representing chlorophytes increased 200-300% since ca. 1950 and total algal biomass more than doubled. Some algal changes began ca. 1900, but shifts in most sedimentary proxies accelerated ca. 1950 commensurate with many human-caused changes to the Earth system. In addition to N deposition, aeolian dust deposition may have contributed phosphorus. Strong increases in summer air and surface water temperatures since 1983 have direct and indirect consequences for high elevation ecosystems. Such warming could have directly enhanced nutrient use and primary production. Indirect consequences of warming include enhanced leaching of nutrients from geologic and cryosphere sources, particularly as glaciers ablate. While we infer causal mechanisms, changes in primary producer communities appear to be without historical precedent and are commensurate with the post-1950 acceleration of global change.

Proceedings of the Royal Society B: Biological Sci↗
USGS2021

Consequences of changing water clarity on the fish and fisheries of the Laurentian Great Lakes

Human-driven environmental change underlies recent changes in water clarity in many of the world’s great lakes, yet our understanding of the consequences of these changes on the fish and fisheries they support remains incomplete. Herein, we offer a framework to organize current knowledge, guide future research, and help fisheries managers understand how water clarity can affect their valued populations. Emphasizing Laurentian Great Lakes findings where possible, we describe how changing water clarity can directly affect fish populations and communities by altering exposure to ultraviolet radiation, foraging success, predation risk, reproductive behavior, or territoriality. We also discuss how changing water clarity can affect fisheries harvest and assessment through effects on fisher behavior and sampling efficiency (i.e., catchability). Finally, we discuss whether changing water clarity can affect understudied aspects of fishery performance, including economic and community benefits. We conclude by identifying generalized predictions and discuss their implications for priority research questions for the Laurentian Great Lakes. Even though the motivation for this work was regional, the breadth of the review and generality of the framework are readily transferable to other freshwater and marine habitats.

Great Lakes↗
USGS1999

A plan for assessing the occurrence and distribution of methyl tert-butyl ether and other volatile organic compounds in drinking water and ambient ground water in the Northeast and Mid-Atlantic regions of the United States

A plan to assess the occurrence and distribution of methyl tert-butyl ether (MTBE) and other volatile organic compounds (VOCs) in drinking water and ambient ground water in the Northeast and Mid-Atlantic regions of the United States was designed to meet two primary objectives. This study will provide the U.S. Environmental Protection Agency with information on potential human exposure to MTBE and other VOCs from drinking water. In addition, the study will further the goals of the U.S. Geological Survey's (USGS) National Water Quality Assessment Program (NAWQA) by providing additional information on the occurrence and distribution of VOCs in ambient ground water beneath a large, highly urbanized part of the Nation. The study will proceed in two phases-a drinking-water assessment (phase 1) and an ambient ground-water assessment (phase 2). The drinking-water assessment will involve compilation, review, and analysis of available water- quality and ancillary data for approximately 20 percent of the community water systems in 12 States in the Northeast and Mid-Atlantic regions. This effort will summarize the occurrence and distribution of MTBE and other VOCs in drinking water supplied by 2,110 community water systems. The ambient ground-water assessment will involve compilation, review, and analysis of data on MTBE and other VOCs from previous USGS studies in the 12-State area, including regional water-quality assessments conducted for the USGS's NAWQA, plus other available State or local datasets. These data will be related, to the extent allowed by the completeness and quality of the data, to land-use patterns, population density, and other anthropogenic and natural factors using statistical tests. The occurrence and distribution of MTBE and other VOCs in ambient ground water and, to the extent possible, drinking water in relation to such factors, will be evaluated.

Open-File Report↗
USGS2018

Environmental contaminants of health-care origin: Exposure and potential effects in wildlife

A diverse range of fauna could be exposed to active pharmaceutical ingredients (APIs) via diet, dermal absorption or bioconcentration. Low level exposures of free-ranging wildlife to APIs has only been demonstrated for a few pathways (e.g., ingestion of fish in estuaries by piscivorous birds), and many remain hypothetical (e.g., ingestion of invertebrates in sludge amended fields by terrestrial vertebrates). Our understanding of API dose-response relationships in wildlife have only been assessed for endocrine disrupting compounds and a few veterinary therapeutics. Drug specific responses at various levels of biological organization are poorly characterized for nearly all wildlife species, and thus our understanding of risk is limited. There is interest in using a read-across approach to fill knowledge gaps for risk. This approach, using data collected in laboratory mammals and humans, would enable predictions for likelihood of adverse effects in wildlife. Given the great diversities in physiologies among species, a combination of in vivo, in vitro and in silico approaches will be required to fill the knowledge gaps for exposure, hazard and risk.

Book chapter↗
USGS2024

Mixed contaminant exposure in tapwater and the potential implications for human-health in disadvantaged communities in California

Water is an increasingly precious resource in California as years of drought, climate change, pollution, as well as an expanding population have all stressed the state's drinking water supplies. Currently, there are increasing concerns about whether regulated and unregulated contaminants in drinking water are linked to a variety of human-health outcomes particularly in socially disadvantaged communities with a history of health risks. To begin to address this data gap by broadly assessing contaminant mixture exposures, the current study was designed to collect tapwater samples from communities in Gold Country, the San Francisco Bay Area, two regions of the Central Valley (Merced/Fresno and Kern counties), and southeast Los Angeles for 251 organic chemicals and 32 inorganic constituents. Sampling prioritized low-income areas with suspected water quality challenges and elevated breast cancer rates. Results indicated that mixtures of regulated and unregulated contaminants were observed frequently in tapwater throughout the areas studied and the types and concentrations of detected contaminants varied by region, drinking-water source, and size of the public water system. Multiple exceedances of enforceable maximum contaminant level(s) (MCL), non-enforceable MCL goal(s) (MCLG), and other health advisories combined with frequent exceedances of benchmark-based hazard indices were also observed in samples collected in all five of the study regions. Given the current focus on improving water quality in socially disadvantaged communities, our study highlights the importance of assessing mixed-contaminant exposures in drinking water at the point of consumption to adequately address human-health concerns (e.g., breast cancer risk). Data from this pilot study provide a foundation for future studies across a greater number of communities in California to assess potential linkages between breast cancer rates and tapwater contaminants.

Callifornia↗
USGS2020

Human behavioral response in the Ridgecrest earthquakes: Assessing immediate actions based on data from “Did You Feel It?”

Human behavioral response to earthquake ground motion has long been a subject of multidisciplinary interest and research. In most versions of seismic intensity scales, human perceptions and behavior are one component of the assignment of intensity. Public health research has shown that actions taken during earthquakes have a significant impact on the incidence of injury or the maintenance of safety. Based on this research, emergency managers and organizations promoting emergency preparedness have advocated strategies such as drop, cover, and hold on (DCHO) and promoted this safety measure through public education and annual drills. The “Did You Feel It?” (DYFI) mapping system (see Data and Resources) based on an online questionnaire developed and maintained by the U.S. Geological Survey has provided opportunities for those who have experienced an earthquake to report this experience worldwide since 2004. The DYFI questionnaire, although designed to assign intensity, also contains questions regarding the behavior in which one has engaged during the earthquake. The questionnaire includes other important information that may elucidate behavioral response to earthquakes, including assigned intensity, emotional reaction, and whether damage occurred at the location where the earthquake was experienced. The very large number of people who completed DYFI questionnaires following the July 2019 Ridgecrest, California, earthquakes provides a robust dataset for analysis and suggests that as intensity and levels of fear increase, behavior becomes more active in terms of physical movement to locations of presumed safety. Among active responses including DCHO, going to a doorway, and running outside, DCHO was the least likely to be implemented. The study provides possible explanations for low participation in DCHO despite active campaigns to promote this strategy.

California↗
USGS1987

Surface-water-quality assessment of the upper Illinois River basin in Illinois, Indiana, and Wisconsin; project description

In 1986, the U.S. Geological Survey began a National Water-Quality Assessment program to (1) provide nationally consistent descriptions of the current status of water quality for a large, diverse, and geographically distributed part of the Nation's surface- and ground-water resources; (2) define, where possible, trends in water quality; and (3) identify and describe the relations of both status and trends in water quality to natural factors and the history of land use and land- and waste-management activities. The program is presently in a pilot phase that will test and modify, as necessary, concepts and approaches in preparation for possible full implementation of the program in the future. The upper Illinois River basin is one of four basins selected to test the concepts and approaches of the surface-water-quality element of the national program. The basin drains 10,949 square miles of Illinois, Indiana, and Wisconsin. Three principal tributaries are the Kankakee and Des Plaines Rivers that join to form the Illinois River and the Fox River. Land use is predominantly agricultural; about 75 percent of the basin is cultivated primarily for production of corn and soybeans. About 13 percent of the basin is urban area, most of which is located in the Chicago metropolitan area. The population of the basin is about 7 million. About 6 million people live in the Des Plaines River basin. Many water-quality issues in the upper Illinois River basin are related to sediment, nutrients, potentially toxic inorganic and organic constituents, and to water-management practices. Occurrence of sediment and the chemical constituents in the rivers and lakes within the basin has the potential to adversely affect the water's suitability for aquatic life, recreation, or, through the consumption of fish, human health. The upper Illinois River basin project consists of five major activities. The first activity--analysis of existing information and preparation of a report that describes recent water-quality conditions and trends--is currently underway. The second activity--fixed-station water-quality sampling at eight stations--began in April 1987 and will last at least 3 years. Water-quality data collected at these stations will be used to determine the frequency of occurrence of constituent concentrations, their annual and seasonal loads, and time trends in concentrations for a selected number of constituents. The third activity will be synoptic water-quality studies. Each study will involve sampling many sites at specific flow conditions and for selected water-quality constituents. Information gained from these studies will supplement informa tion gained from fixed-station sampling. A synoptic study of streambed sediments is tentatively planned for the summer of 1987 to describe the occurrence and distribution of trace elements in the basin. The fourth activity will consist of one or more topical subbasin or river-reach studies. The purpose of such studies is to better define certain water-quality conditions in specific areas and gain an understanding of the processes affecting the observed conditions. The fifth activity is the preparation of reports that will describe results from each of the first four activities. Quality assurance and coordination are being provided at both the national and pilot-project levels. A technical quality-assurance plan that addresses all aspects of sample collection, analysis, and reporting is being prepared at the national level. This plan will be appended as needed at the pilot-project level. A National Coordinating Work Group that functions under the auspices of the Interagency Advisory Committee on Water Data and the Advisory Committee on Water Data for Public Use has been established at the national level. A local liaison committee consisting of representatives from Federal, State, and local agencies has been established to enhance communication and to ensure that the scientific information produced by the

Open-File Report↗
USGS2005

Field guide to the major organisms and processes building reefs and islands of the Dry Tortugas: the Carnegie Dry Tortugas Laboratory Centennial Celebration (1905-2005)

This guide to the geology and biology of the Dry Tortugas is divided into four sections: 1) geologic and anthropogenic features you will pass on your trip to and from the Tortugas, 2) a summary of items of Tortugas geologic, historic, and human interest and what you will experience at Loggerhead Key while walking and snorkeling, 3) a summary of recent coral-monitoring results, and 4) an Appendix with tributes to some of the significant research accomplishments of researchers at the laboratory between 1905 and 1939.

Florida↗
USGS2013

Ecotoxicology of organochlorine chemicals in birds of the Great Lakes

Silent Spring was fulfilled in the United States with passage of environmental legislation such as the Clean Water Act, the Federal Insecticide, Fungicide, and Rodenticide Act, and the Toxic Substance Control Act in the 1970s. Carson's writings, television interviews, and testimony before Congress alerted a nation and the world to the unintended effects of persistent, bioaccumulative chemicals on populations of fish, wildlife, and possibly humans. Her writings in the popular press brought attention to scientific findings that declines in populations of a variety of birds were directly linked to the widespread use of dichlorodiphenyltrichloroethane (DDT) in agriculture, public health, and horticulture. By the 1970s, DDT and other persistent organic pollutants (POPs) were being banned or phased out, and the intent of these regulatory acts became apparent in a number of locations across the United States, including the Great Lakes. Concentrations of DDT and its major product of transformation, dichlorodiphenylchloroethane (DDE), were decreasing in top predators, such as bald eagles (Haliaeetus leucocephalus), osprey (Pandion haliaetus), colonial waterbirds, and other fish-eating wildlife. Eggshell thinning and the associated mortality of bird embryos caused by DDE had decreased in the Great Lakes and elsewhere by the early 1980s.

Environmental Toxicology and Chemistry↗
USGS2014

From headwaters to coast: Influence of human activities on water quality of the Potomac River Estuary

The natural aging process of Chesapeake Bay and its tributary estuaries has been accelerated by human activities around the shoreline and within the watershed, increasing sediment and nutrient loads delivered to the bay. Riverine nutrients cause algal growth in the bay leading to reductions in light penetration with consequent declines in sea grass growth, smothering of bottom-dwelling organisms, and decreases in bottom-water dissolved oxygen as algal blooms decay. Historically, bay waters were filtered by oysters, but declines in oyster populations from overfishing and disease have led to higher concentrations of fine-sediment particles and phytoplankton in the water column. Assessments of water and biological resource quality in Chesapeake Bay and tributaries, such as the Potomac River, show a continual degraded state. In this paper, we pay tribute to Owen Bricker’s comprehensive, holistic scientific perspective using an approach that examines the connection between watershed and estuary. We evaluated nitrogen inputs from Potomac River headwaters, nutrient-related conditions within the estuary, and considered the use of shellfish aquaculture as an in-the-water nutrient management measure. Data from headwaters, nontidal, and estuarine portions of the Potomac River watershed and estuary were analyzed to examine the contribution from different parts of the watershed to total nitrogen loads to the estuary. An eutrophication model was applied to these data to evaluate eutrophication status and changes since the early 1990s and for comparison to regional and national conditions. A farm-scale aquaculture model was applied and results scaled to the estuary to determine the potential for shellfish (oyster) aquaculture to mediate eutrophication impacts. Results showed that (1) the contribution to nitrogen loads from headwater streams is small (about 2 %) of total inputs to the Potomac River Estuary; (2) eutrophic conditions in the Potomac River Estuary have improved in the upper estuary since the early 1990s, but have worsened in the lower estuary. The overall system-wide eutrophication impact is high, despite a decrease in nitrogen loads from the upper basin and declining surface water nitrate nitrogen concentrations over that period; (3) eutrophic conditions in the Potomac River Estuary are representative of Chesapeake Bay region and other US estuaries; moderate to high levels of nutrient-related degradation occur in about 65 % of US estuaries, particularly river-dominated low-flow systems such as the Potomac River Estuary; and (4) shellfish (oyster) aquaculture could remove eutrophication impacts directly from the estuary through harvest but should be considered a complement—not a substitute—for land-based measures. The total nitrogen load could be removed if 40 % of the Potomac River Estuary bottom was in shellfish cultivation; a combination of aquaculture and restoration of oyster reefs may provide larger benefits.

Maryland, Pennsylvania, Virginia, West Virginia↗
USGS2017

Hydrological connectivity in intermittent rivers and ephemeral streams

In intermittent rivers and ephemeral streams (hereafter, IRES), hydrological connectivity mediated by either flowing or nonflowing water extends along three spatial dimensions—longitudinal, lateral, and vertical—and varies over time. Flow intermittence disrupts this connectivity, operating through complex hydrological transitions (e.g., between flowing and nonflowing phases). These transitions occur concurrently and interact along all three spatial dimensions, primarily driven by flow regime and catchment geomorphology, modified by human activities. Longitudinally, streamflow cessation and drying interrupt hydrological connectivity, contributing to physicochemical patchiness, habitat isolation, and fragmentation of metapopulations and metacommunities. Laterally, hydrological connectivity established during overbank flows is lost when water levels fall, reducing water-mediated transfers of energy, materials, and organisms from the floodplain and riparian zone. Vertically, flow cessation impairs exchange of surface and shallow groundwater, severely altering hydrological, chemical, and microbial gradients within the sediments. Concurrent interactions and physical discontinuities in hydrological connectivity along these three dimensions produce complex mosaics of physicochemical patches at different scales whose boundaries fluctuate over time in response to the flow regime. This complex patchiness underpins the characteristic physical, chemical, and biological diversity at multiple scales along longitudinal, lateral, and vertical hydrological dimensions in IRES.

Book chapter↗
USGS1999

Shallow ground-water quality in the Coastal Plain of Columbia, South Carolina, 1996

As part of the National Water-Quality Assessment (NAWQA) Program, the U.S. Geological Survey (USGS) oversaw the installation of 30 shallow monitoring wells in the Columbia, South Carolina metropolitan area. The ground water sampled from these wells was used to study the recent effects of human activities on shallow ground water in an urban setting. Well locations were selected in residential and commercial areas constructed between 1960 and 1990 while all industrial and agricultural areas were avoided. Samples were collected and analyzed for major ions, nutrients, pesticides, and volatile organic compounds (VOCs) dunng 1996. This report describes the results of this investigation of shallow ground-water quality.

North Carolina, South Carolina↗
USGS2007

Ground-Water Quality of the Northern High Plains Aquifer, 1997, 2002-04

An assessment of ground-water quality in the northern High Plains aquifer was completed during 1997 and 2002-04. Ground-water samples were collected at 192 low-capacity, primarily domestic wells in four major hydrogeologic units of the northern High Plains aquifer-Ogallala Formation, Eastern Nebraska, Sand Hills, and Platte River Valley. Each well was sampled once, and water samples were analyzed for physical properties and concentrations of nitrogen and phosphorus compounds, pesticides and pesticide degradates, dissolved solids, major ions, trace elements, dissolved organic carbon (DOC), radon, and volatile organic compounds (VOCs). Tritium and microbiology were analyzed at selected sites. The results of this assessment were used to determine the current water-quality conditions in this subregion of the High Plains aquifer and to relate ground-water quality to natural and human factors affecting water quality. Water-quality analyses indicated that water samples rarely exceeded established U.S. Environmental Protection Agency public drinking-water standards for those constituents sampled; 13 of the constituents measured or analyzed exceeded their respective standards in at least one sample. The constituents that most often failed to meet drinking-water standards were dissolved solids (13 percent of samples exceeded the U.S. Environmental Protection Agency Secondary Drinking-Water Regulation) and arsenic (8 percent of samples exceeded the U.S. Environmental Protection Agency Maximum Contaminant Level). Nitrate, uranium, iron, and manganese concentrations were larger than drinking-water standards in 6 percent of the samples. Ground-water chemistry varied among hydrogeologic units. Wells sampled in the Platte River Valley and Eastern Nebraska units exceeded water-quality standards more often than the Ogallala Formation and Sand Hills units. Thirty-one percent of the samples collected in the Platte River Valley unit had nitrate concentrations greater than the standard, 22 percent exceeded the manganese standard, 19 percent exceeded the sulfate standard, 26 percent exceeded the uranium standard, and 38 percent exceeded the dissolved-solids standard. In addition, 78 percent of samples had at least one detectable pesticide and 22 percent of samples had at least one detectable VOC. In the Eastern Nebraska unit, 30 percent of the samples collected had dissolved-solids concentrations larger than the standard, 23 percent exceeded the iron standard, 13 percent exceeded the manganese standard, 10 percent exceeded the arsenic standard, 7 percent exceeded the sulfate standard, 7 percent exceeded the uranium standard, and 7 percent exceeded the selenium standard. No samples exceeded the nitrate standard. Thirty percent of samples had at least one detectable pesticide compound and 10 percent of samples had at least one detectable VOC. In contrast, the Sand Hills and Ogallala Formation units had fewer detections of anthropogenic compounds and drinking-water exceedances. In the Sand Hills unit, 15 percent of the samples exceeded the arsenic standard, 4 percent exceeded the nitrate standard, 4 percent exceeded the uranium standard, 4 percent exceeded the iron standard, and 4 percent exceeded the dissolved-solids standard. Fifteen percent of samples had at least one pesticide compound detected and 4 percent had at least one VOC detected. In the Ogallala Formation unit, 6 percent of water samples exceeded the arsenic standard, 4 percent exceeded the dissolved-solids standard, 3 percent exceeded the nitrate standard, 2 percent exceeded the manganese standard, 1 percent exceeded the iron standard, 1 percent exceeded the sulfate standard, and 1 percent exceeded the uranium standard. Eight percent of samples collected in the Ogallala Formation unit had at least one pesticide detected and 6 percent had at least one VOC detected. Differences in ground-water chemistry among the hydrogeologic units were attributed to variable depth to water, depth of the well screen below the water table, reduction-oxidation conditions, ground-water residence time, interactions with surface water, composition of aquifer sediments, extent of cropland, extent of irrigated land, and fertilizer application rates.

Scientific Investigations Report↗
USGS2016

Arsenic in groundwater of Licking County, Ohio, 2012—Occurrence and relation to hydrogeology

Arsenic concentrations were measured in samples from 168 domestic wells in Licking County, Ohio, to document arsenic concentrations in a wide variety of wells and to identify hydrogeologic factors associated with arsenic concentrations in groundwater. Elevated concentrations of arsenic (greater than 10.0 micrograms per liter [µg/L]) were detected in 12 percent of the wells (about 1 in 8). The maximum arsenic concentration of about 44 µg/L was detected in two wells in the same township. A subset of 102 wells was also sampled for iron, sulfate, manganese, and nitrate, which were used to estimate redox conditions of the groundwater. Elevated arsenic concentrations were detected only in strongly reducing groundwater. Almost 20 percent of the samples with iron concentrations high enough to produce iron staining (greater than 300 µg/L) also had elevated concentrations of arsenic. In groundwater, arsenic primarily occurs as two inorganic species—arsenite and arsenate. Arsenic speciation was determined for a subset of nine samples, and arsenite was the predominant species. Of the two species, arsenite is more difficult to remove from water, and is generally considered to be more toxic to humans. Aquifer and well-construction characteristics were compiled from 99 well logs. Elevated concentrations of arsenic (and iron) were detected in glacial and bedrock aquifers but were more prevalent in glacial aquifers. The reason may be that the glacial deposits typically contain more organic carbon than the Paleozoic bedrock. Organic carbon plays a role in the redox reactions that cause arsenic (and iron) to be released from the aquifer matrix. Arsenic concentrations were not significantly different for different types of bedrock (sandstone, shale, sandstone/shale, or other). However, arsenic concentrations in bedrock wells were correlated with two well-construction characteristics; higher arsenic concentrations in bedrock wells were associated with (1) shorter open intervals and (2) deeper open intervals, relative to the water level. The spatial distribution of arsenic concentrations was compared to hydrogeologic characteristics of Licking County. Elevated concentrations of arsenic (and iron) were associated with areas of flat topography and thick (greater than 100 feet),clay-rich glacial deposits. These characteristics are conducive to development of strongly reducing redox conditions, which can cause arsenic associated with iron oxyhydroxides in the aquifer matrix to be released to the groundwater. Hydrogeologic characteristics conducive to the development of strongly reducing groundwater are relatively wide-spread in the western part of Licking County, which is part of the Central Lowland physiographic province. In this area, a thick layer of clay-rich glacial deposits obscures the bedrock surface and creates flat to gently rolling landscape with poorly developed drainage networks. In the eastern part of the county, which is part of the Appalachian Plateaus physiographic province, the landscape includes steep-sided valleys and bedrock uplands. In this area, elevated arsenic concentrations were detected in buried valleys but not in the bedrock uplands, where glacial deposits are thin or absent. The observation that elevated concentrations of arsenic (and iron) were more prevalent in the western part of Licking County is true for both glacial and bedrock aquifers. In Licking County, thick, clay-rich glacial deposits (and elevated concentrations of arsenic) are associated with two hydrogeologic settings—buried valley and complex thick drift. Most wells in the buried-valley setting had low arsenic concentrations, but a few samples had very high concentrations (30–44 µg/L) and very reducing redox conditions (methanogenic and near-methanogenic). For wells in the complex-thick-drift setting, elevated arsenic concentrations are more prevalent, but the maximum concentration was lower (about 21 µg/L). Similar observations were made about arsenic concentrations in parts of southwestern Ohio. The hydrogeologic settings and characteristics associated with arsenic in Licking County also exist in other parts of Ohio. The statewide extent of these characteristics roughly corresponds to areas where elevated concentrations of arsenic are known to exist. This preliminary conceptual model can be tested and revised as additional wells are sampled for arsenic.

Ohio↗
USGS2013

Ice-age megafauna in Arctic Alaska: extinction, invasion, survival

Radical restructuring of the terrestrial, large mammal fauna living in arctic Alaska occurred between 14,000 and 10,000 years ago at the end of the last ice age. Steppe bison, horse, and woolly mammoth became extinct, moose and humans invaded, while muskox and caribou persisted. The ice age megafauna was more diverse in species and possibly contained 6× more individual animals than live in the region today. Megafaunal biomass during the last ice age may have been 30× greater than present. Horse was the dominant species in terms of number of individuals. Lions, short-faced bears, wolves, and possibly grizzly bears comprised the predator/scavenger guild. The youngest mammoth so far discovered lived ca 13,800 years ago, while horses and bison persisted on the North Slope until at least 12,500 years ago during the Younger Dryas cold interval. The first people arrived on the North Slope ca 13,500 years ago. Bone-isotope measurements and foot-loading characteristics suggest megafaunal niches were segregated along a moisture gradient, with the surviving species (muskox and caribou) utilizing the warmer and moister portions of the vegetation mosaic. As the ice age ended, the moisture gradient shifted and eliminated habitats utilized by the dryland, grazing species (bison, horse, mammoth). The proximate cause for this change was regional paludification, the spread of organic soil horizons and peat. End-Pleistocene extinctions in arctic Alaska represent local, not global extinctions since the megafaunal species lost there persisted to later times elsewhere. Hunting seems unlikely as the cause of these extinctions, but it cannot be ruled out as the final blow to megafaunal populations that were already functionally extinct by the time humans arrived in the region.

Alaska↗
USGS2025

Nocardia cyriacigeorgica in a Mallard (Anas platyrhynchos) from Arizona, USA

Nocardia spp. are opportunistic pathogens of humans, domestic animals, and wildlife that can cause high levels of morbidity and mortality. Here, we present a unique case of nocardial airsacculitis in a free-ranging mallard ( Anas platyrhynchos ) from Arizona, USA, and compare it to the hosts, geographic distribution, diagnostic methodology, and infection site of known nocardiosis cases in birds. A gross necropsy, histopathology, and bacterial culture were performed. There were no gross findings associated with the nocardiosis. Histopathology showed multiple granulomas expanding the air sac with intralesional filamentous bacteria that were Grocott’s methenamine silver-positive, Fite–Faraco and Ziehl–Neelsen acid-fast, positive with the Periodic acid–Schiff reaction, and variably Gram-positive. The organism was isolated in culture and identified as Nocardia cyriacigeorgica based on the sequencing of a 463 bp portion of the 16S rRNA gene. While reports of nocardiosis in the class Aves are rare and some are possibly misdiagnosed due to limited diagnostics, cases are reported globally, sometimes resulting in epizootics. More information is needed to understand whether immunosuppression plays a role in disease development in birds. Known to be an emerging pathogen in humans, N. cyriacigeorgica can be considered as a differential diagnosis for pulmonary and potentially cutaneous or disseminated infections in birds.

Arizona↗