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At least 991 records · Page 55Linked to original sources
USGS2005

Leaf litter breakdown, microbial respiration and shredder production in metal-polluted streams

1. If species disproportionately influence ecosystem functioning and also differ in their sensitivities to environmental conditions, the selective removal of species by anthropogenic stressors may lead to strong effects on ecosystem processes. We evaluated whether these circumstances held for several Colorado, U.S.A. streams stressed by Zn. 2. Benthic invertebrates and chemistry were sampled in five second-third order streams for 1 year. Study streams differed in dissolved metal concentrations, but were otherwise similar in chemical and physical characteristics. Secondary production of leaf-shredding insects was estimated using the increment summation and size-frequency methods. Leaf litter breakdown rates were estimated by retrieving litter-bags over a 171 day period. Microbial activity on leaf litter was measured in the laboratory using changes in oxygen concentration over a 48 h incubation period. 3. Dissolved Zn concentrations varied eightfold among two reference and three polluted streams. Total secondary production of shredders was negatively associated with metal contamination. Secondary production in reference streams was dominated by Taenionema pallidum. Results of previous studies and the current investigation demonstrate that this shredder is highly sensitive to metals in Colorado headwater streams. Leaf litter breakdown rates were similar between reference streams and declined significantly in the polluted streams. Microbial respiration at the most contaminated site was significantly lower than at reference sites. 4. Our results supported the hypothesis that some shredder species contribute disproportionately to leaf litter breakdown. Furthermore, the functionally dominant taxon was also the most sensitive to metal contamination. We conclude that leaf litter breakdown in our study streams lacked functional redundancy and was therefore highly sensitive to contaminant-induced alterations in community structure. We argue for the necessity of simultaneously measuring community structure and ecosystem function in anthropogenically stressed ecosystems.

Freshwater Biology↗
USGS1997

Temporal trends of selected agricultural chemicals in Iowa's groundwater, 1982-1995: Are things getting better?

Since 1982, the Iowa Groundwater Monitoring (IGWM) Program has been used to sample untreated groundwater from Iowa municipal wells for selected agricultural chemicals. This long-term database was used to determine if concentrations of select agricultural chemicals in groundwater have changed with time. Nitrate, alachlor [2-chloro-2′-6′-diethyl- N -(methoxymethyl)-acetanilide], atrazine (2-chloro-4-ethylamino-6-isopropylamino- s -triazine), cyanazine [2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl]amino]-2-methylpropionitrile)], and metolachlor [2-chloro- N -(2-ethyl-6-methylphenyl)- N -(2-methoxy-1-methylethyl) acetamide] were selected for this temporal analysis of the data. Conclusive temporal changes in frequency of detection and median chemical concentrations were found only for atrazine (decrease) and metolachlor (increase). The greatest temporal chemical changes occurred in the shallowest wells and in alluvial aquifers—both relating to groups of wells generally having the youngest groundwater age. The temporal patterns found for atrazine and metolachlor are consistent with their patterns of chemical use and/or application rates and are suggestive of a causal relation. Only continued data collection, however, will indicate if the trends in chemical concentrations described here represent long-term temporal patterns or only short-term changes in groundwater. No definitive answers could be made in regards to the question of overall improvements in groundwater quality with respect to agricultural chemical contamination and time, due to the inherent problems with the simplistic measurement of overall severity (summation of alachlor + atrazine + cyanazine + metolachlor concentrations) examined for this study. To adequately determine if there is an actual decreasing trend in the overall severity of contamination (improving groundwater quality), the collection of additional water-chemistry data and the investigation of other measures of severity are needed.

Iowa↗
USGS2003

Identifying relationships between baseflow geochemistry and land use with synoptic sampling and R-mode factor analysis

The relationship between land use and stream chemistry is often explored through synoptic sampling of rivers at baseflow conditions. However, baseflow chemistry is likely to vary temporally and spatially with land use. The purpose of our study is to examine the usefulness of the synoptic sampling approach for identifying the relationship between complex land use configurations and stream water quality. This study compares biogeochemical data from three synoptic sampling events representing the temporal variability of baseflow chemistry and land use using R - mode factor analysis . Separate R - mode factor analyses of the data from individual sampling events yielded only two consistent factors. Agricultural activity was associated with elevated levels of Ca 2+ , Mg 2+ , alkalinity, and frequently K + , SO 2- 4 , and NO - 3 . Urban areas were associated with higher concentrations of Na + , K + , and Cl - . Other retained factors were not consistent among sampling events, and some factors were difficult to interpret in the context of biogeochemical sources and processes. When all data were combined, further associations were revealed such as an inverse relationship between the proportion of wetlands and stream nitrate concentrations. We also found that barren lands were associated with elevated sulfate levels. This research suggests that an individual sampling event is unlikely to characterize adequately the complex processes controlling interactions between land use and stream chemistry. Combining data collected over two years during three synoptic sampling events appears to enhance our ability to understand processes linking stream chemistry and land use.

Michigan↗
USGS2019

Columbia Environmental Research Center

The U.S. Geological Survey Columbia Environmental Research Center performs research to solve challenging environmental problems related to contaminants and habitat alterations in aquatic and terrestrial ecosystems. The research is interdisciplinary and pursued through partnerships within the U.S. Geological Survey and with national, international, state, and local agencies; nongovernmental organizations; and universities. Research is prioritized to provide science to the U.S. Department of the Interior and other natural resource management agencies to inform rehabilitation of degraded habitats and imperiled fish and wildlife populations. The Columbia Environmental Research Center was established in 1966 in Columbia, Missouri, as the U.S. Fish and Wildlife Service’s Fish Pesticide Research Laboratory; the Columbia Environmental Research Center was incorporated into the U.S. Geological Survey in 1996. The U.S. Geological Survey’s staff of 130 includes 90 scientists of which one-half have advanced degrees in ecology, toxicology, biology, biochemistry, chemistry, hydrology, geology, and information technology.

Missouri↗
USGS2004

Biological assessment of streams in the Indianapolis Metropolitan Area, Indiana, 1999-2001

During 1999?2001, benthic invertebrates and fish were sampled to describe biological communities in the White River and selected tributaries in the Indianapolis Metropolitan Area in Indiana. Twelve sites (six on the White River and six on tributaries) were sampled biannually for benthic invertebrates and annually for fish. The information complements water-chemistry data collected by the Indianapolis Department of Public Works in the study area. Evaluation of the habitat for sites in the study area was done, using a Qualitative Habitat Evaluation Index (QHEI) developed by the Ohio Environmental Protection Agency. The QHEI scores basin and habitat characteristics for each site, with a maximum possible score of 100. Higher scores indicate better habitat conditions for biotic communities. The QHEI scores for sites on the White River ranged from 55 at the Harding site to 71 at the Waverly site; scores on the tributaries ranged from 45 on Pogues Run to 82 on Williams Creek. A total of 151 taxa were identified from the benthic-invertebrate samples. The Ephemeroptera, Plecoptera, and Trichoptera (EPT) Index scores for sites on the White River ranged from 0 at the Harding site to 15 at the Nora site. The Nora site, which is upstream from Indianapolis, generally scored the highest of all White River sites. Sites in the immediate vicinity of Indianapolis scored the lowest and indicate a negative effect on benthic-invertebrate communities in that reach. EPT Index scores increased in the farthest downstream reaches, which indicate that water-quality conditions had improved in comparison to sites in Indianapolis. For the tributary sites, EPT Index values ranged from 0 at Pogues Run to 16 at Buck Creek. Tributary sites on Fall Creek, Pleasant Run, and Pogues Run consistently scored 7 or lower; sites on Buck Creek, Eagle Creek, and Williams Creek scored 7 or higher. Hilsenhoff Biotic Index (HBI) scores ranged from 4.9 (good) to 9.6 (very poor) for the White River sites and from 5.2 (good) to 8.0 (poor) for the tributary sites. The lowest scores among the White River sites were at the Nora site, indicating the best water-quality conditions were where the White River enters Marion County. The highest HBI scores were at the Morris and Harding sites, indicating the least-favorable water-quality conditions of all the White River sites. Of the tributary sites, HBI scores for Buck, Eagle, and Williams Creeks indicate fair water-quality conditions; HBI scores for Pleasant Run and Pogues Run were the highest, indicating relatively poor water-quality conditions. On the White River, the highest Invertebrate Community Index (ICI) scores, which indicate the best benthic-invertebrate conditions, were at the Nora site. Conditions were fair to poor in the downtown Indianapolis area; ICI scores indicate slight improvement in the downstream reaches of the study area. Of the tributary sites, Buck Creek was the only site with ICI scores indicating exceptional water quality. Williams Creek ICI scores indicate good water quality; the remaining tributary-site scores reflect fair conditions. A total of 74 species and 3 hybrids of fish were identified during the study period. The Cyprinidae (carps and minnows) was the largest group of fish identified and consisted of more than half of all fish collected. The most numerous species was the central stoneroller (Campostoma anomalum), which accounted for almost 25 percent of the fish identified. Two nonnative species, the koi carp (Cyprinus carpio) and the western mosquitofish (Gambusia affinis), and one species classified as an Indiana species of special concern, the northern studfish (Fundulus catenatus), also were collected during the study. Indiana Index of Biotic Integrity (IBI) and Ohio Index of Biotic Integrity scores were calculated to show the condition of the fish communities at each site. Results of the Indiana IBI calculations showed no apparent differences in scores among the Wh

Water-Resources Investigations Report↗
USGS2011

Tracking solutes and water from subsurface drip irrigation application of coalbed methane-produced waters, Powder River Basin, Wyoming

One method to beneficially use water produced from coalbed methane (CBM) extraction is subsurface drip irrigation (SDI) of croplands. In SDI systems, treated CBM water (injectate) is supplied to the soil at depth, with the purpose of preventing the buildup of detrimental salts near the surface. The technology is expanding within the Powder River Basin, but little research has been published on its environmental impacts. This article reports on initial results from tracking water and solutes from the injected CBM-produced waters at an SDI system in Johnson County, Wyoming. In the first year of SDI operation, soil moisture significantly increased in the SDI areas, but well water levels increased only modestly, suggesting that most of the water added was stored in the vadose zone or lost to evapotranspiration. The injectate has lower concentrations of most inorganic constituents relative to ambient groundwater at the site but exhibits a high sodium adsorption ratio. Changes in groundwater chemistry during the same period of SDI operation were small; the increase in groundwater-specific conductance relative to pre-SDI conditions was observed in a single well. Conversely, groundwater samples collected beneath another SDI field showed decreased concentrations of several constituents since the SDI operation. Groundwater-specific conductance at the 12 other wells showed no significant changes. Major controls on and compositional variability of groundwater, surface water, and soil water chemistry are discussed in detail. Findings from this research provide an understanding of water and salt dynamics associated with SDI systems using CBM-produced water.

Wyoming↗
USGS2020

Sphalerite oxidation in seawater with covellite: Implications for seafloor massive sulfide deposits and mine waste

Metal sulfide minerals exist in several marine environments and are in thermodynamic disequilibrium with oxygenated seawater from the time of their formation. Oxidation is both ubiquitous and heterogeneous, as observational and experimental evidence demonstrates that sulfide minerals may oxidize completely on decadal timescales (hydrothermal plumes) or incompletely in billions of years (mineral deposits); however, the processes, rates, and interactions among minerals as oxidative dissolution occurs are not well understood. Added impetus to understanding these processes exists due to the potential for mining of seafloor massive sulfide deposits and potential environmental impacts of that activity. Here, we present a laboratory-based experimental study on the galvanic oxidation of sphalerite and synthesized zinc sulfide and coupled to covellite. We find that, in contrast to single-mineral reactions, coupled mineral reactions are at least 2 orders of magnitude more rapid, light independent, and have a lower apparent activation energy for oxidation. These results begin to provide insight into observed differences between laboratory and environmentally observed oxidation rates and are a step in the direction of more accurately predicting environmental rates as well as any changes to those rates from anthropogenic disturbances.

ACS Earth and Space Chemistry↗
USGS2011

Stream-groundwater interactions

Streams and their surrounding catchments exchange water and solutes on a range of physical scales. Exchange with the stream may extend into the interstitial areas of the streambed, the hyporheic zone, the riparian area, or the catchment's groundwater flow system. Even at the smaller scales, the exchanges significantly influence solute transport, nutrient cycling, and the aquatic ecosystem. Over the recent decades, considerable attention has been given to the solute transport aspects of stream–groundwater interactions. Stream–groundwater interactions are now being recognized as practical matters to be considered in environmental issues, such as stream restoration and fish habitat. In this chapter, the emphasis is on introducing (1) the breadth of hydrologic interactions between streams and groundwater and (2) the importance of interpreting these interactions to understanding stream chemistry and ecology.

Book chapter↗
USGS2024

A new species of benthic ostracod Tuberoloxoconcha: A proxy for glacioeustatic sea-level changes in the Gulf of Corinth

In 2017, sediment cores were retrieved from sites M0080, M0079, and M0078 in the Corinth basin during IODP Expedition 381. This study focuses on the Holocene and middle Pleistocene ostracod assemblages retrieved from sites M0080, in the Gulf of Alkyonides, and M0078 in the Corinth Gulf. It explores the paleoenvironmental constraints that affected the Tuberoloxoconcha species' distribution in these two sites and investigates the stratigraphic appearance of the new species Tuberoloxoconcha aielloi in the Corinth basin during deglacial and glacial periods over the last 400,000 years. In the Gulf of Corinth, fossil assemblages dominated by T. aielloi n. sp. have identified brackish shallow water environments corresponding to deglacial and glacial phases, when the basin was likely semi-isolated from Mediterranean waters, with high fluvial input lowering the salinity of the waterbody. The study highlights the discontinuous occurrence of T. aielloi and its morphotypes, identifying cold phases during MIS 10 and MIS 7d, and warmer phases during MISs 2–3-4-5a. The variability in ornamentation potentially reflects different water chemistry in the two sites. The post-400 ky appearance of T. aielloi , coinciding with the development of the marine connection through the Rion Strait, implies a Mediterranean/Atlantic origin for the genus. This study provides insights into the environmental conditions and evolutionary history of T. aielloi species in the Corinth basin, contributing to a broader understanding of benthic species' responses to past and future sea level changes.

Gulf of Corinth↗
USGS2022

Ocean acidification in the Gulf of Mexico: Drivers, impacts, and unknowns

Ocean acidification (OA) has resulted in global-scale changes in ocean chemistry, which can disturb marine organisms and ecosystems. Despite its extensively populated coastline, many marine-dependent communities, and valuable economies, the Gulf of Mexico (GOM) remains a relatively understudied region with respect to acidification. In general, the warm waters of the GOM are better buffered from acidification compared to higher latitude seas, yet long-term acidification has been documented in several GOM regions. OA within the GOM is recognized as spatially variable, particularly within the coastal zone where numerous physical and biogeochemical processes contribute to carbonate chemistry dynamics. The historical progression of OA within the entire GOM is difficult to assess because only a few dedicated long-term monitoring sites have recently been established, and full-water column observations are limited. However, environmental drivers on smaller scales that affect GOM acidification were found to include freshwater, nutrient, and carbonate discharge from large rivers; ocean warming, circulation and residence times; and episodic extreme weather events. GOM marine ecosystems provide essential services, including coastline protection and carbon dioxide removal, and habitats for many marine species that are economically and ecologically important. However, organismal and ecosystem responses to OA are not well constrained for the GOM due to a lack of studies examining the specific effects of OA on regionally relevant species under contemporary and projected conditions. Tackling the vast number of remaining scientific unknowns in this region can be best coordinated through regional capacity networks, such as the Gulf of Mexico Coastal Acidification Network (GCAN), working to achieve a system-wide understanding of Gulf OA and its impacts. Here we synthesize the current peer-reviewed literature on GOM acidification across the ocean-estuarine continuum and identify critical knowledge, research, and monitoring gaps that require future attention.

Progress in Oceanography↗
USGS2003

Covariance of bacterioplankton composition and environmental variables in a temperate delta system

We examined seasonal and spatial variation in bacterioplankton composition in the Sacramento-San Joaquin River Delta (CA) using terminal restriction fragment length polymorphism (T-RFLP) analysis. Cloned 16S rRNA genes from this system were used for putative identification of taxa dominating the T-RFLP profiles. Both cloning and T-RFLP analysis indicated that Actinobacteria , Verrucomicrobia , Cytophaga-Flavobacterium and Proteobacteria were the most abundant bacterioplankton groups in the Delta. Despite the broad variety of sampled habitats (deep water channels, lakes, marshes, agricultural drains, freshwater and brackish areas), and the spatial and temporal differences in hydrology, temperature and water chemistry among the sampling campaigns, T-RFLP electropherograms from all samples were similar, indicating that the same bacterioplankton phylotypes dominated in the various habitats of the Delta throughout the year. However, principal component analysis (PCA) and partial least-squares regression (PLS) of T-RFLP profiles revealed consistent grouping of samples on a seasonal, but not a spatial, basis. b- Proteobacteria related to Ralstonia , Actinobacteria related to Microthrix , and b- Proteobacteria identical to the environmental Clone LD12 had the highest relative abundance in summer/fall T-RFLP profiles and were associated with low river flow, high pH, and a number of optical and chemical characteristics of dissolved organic carbon (DOC) indicative of an increased proportion of phytoplankton-produced organic material as opposed to allochthonous, terrestrially derived organic material. On the other hand, Geobacter -related b- Proteobacteria showed a relative increase in abundance in T-RFLP analysis during winter/spring, and probably were washed out from watershed soils or sediment. Various phylotypes associated with the same phylogenetic division, based on tentative identification of T-RFLP fragments, exhibited diverse seasonal patterns, suggesting that ecological roles of Delta bacterioplankton were partitioned at the genus or species level.

Aquatic Microbial Ecology↗
USGS2013

Managing the effects of endocrine disrupting chemicals in wastewater-impacted streams

A revolution in analytical instrumentation circa 1920 greatly improved the ability to characterize chemical substances. This analytical foundation resulted in an unprecedented explosion in the design and production of synthetic chemicals during and post-World War II. What is now often referred to as the 2nd Chemical Revolution has provided substantial societal benefits; with modern chemical design and manufacturing supporting dramatic advances in medicine, increased food production, and expanding gross domestic products at the national and global scales as well as improved health, longevity, and lifestyle convenience at the individual scale. Presently, the chemical industry is the largest manufacturing sector in the United States (U.S.) and the second largest in Europe and Japan, representing approximately 5% of the Gross Domestic Product (GDP) in each of these countries. At the turn of the 21st century, the chemical industry was estimated to be worth more than $1.6 trillion and to employ over 10 million people, globally. During the first half of the 20th century, the chemical sector expanded rapidly, the chemical industry enjoyed a generally positive status in society, and chemicals were widely appreciated as fundamental to individual and societal quality of life. Starting in the 1960s, however, the environmental costs associated with the chemical industry increasingly became the focus, due in part to the impact of books like “Silent Spring” and “Our Stolen Future” and to a number of highly publicized environmental disasters. Galvanizing chemical industry disasters included the 1976 dioxin leak north of Milan, Italy, the Love Canal evacuations in Niagara, New York beginning in 1978, and the Union Carbide leak in Bhopal, India in 1984. Understanding the environmental impact of synthetic compounds is essential to any informed assessment of net societal benefit, for the simple reason that any chemical substance that is in commercial production or use will eventually find its way to the environment. Not surprisingly given the direct link to profits, manufacturers intensely investigate and routinely document the potential benefits of new chemicals and chemical products. In contrast, the environmental risks associated with chemical production and uses are often investigated less intensely and are poorly communicated. An imbalance in the risk-benefit analysis of any synthetic chemical substance or naturally occurring chemical, which presence and concentration in the environment largely reflects human activities and management, is a particular concern owing to the fundamental link between chemistry and biology. Biological organisms are intrinsically a homeostatic balance of innumerable internal and external chemical interactions and, thus, inherently sensitive to changes in the external chemical environment.

Book chapter↗
USGS2010

Hydrostratigraphy, soil/sediment chemistry, and water quality, Potomac-Raritan-Magothy aquifer system, Puchack Well Field Superfund site and vicinity, Pennsauken Township, Camden County, New Jersey, 1997-2001

Drinking-water supplies from the Potomac-Raritan-Magothy aquifer system at the Puchack well field in Pennsauken Township, Camden County, New Jersey, have been contaminated by hexavalent chromium-the most toxic and mobile form-at concentrations exceeding the New Jersey maximum contaminant level of 100 micrograms per liter. Also, scattered but widespread instances of volatile organic compounds (primarily trichloroethylene) at concentrations that exceed their respective maximum contaminant levels in the area's ground water have been reported. Because inorganic and organic contaminants are present in the ground water underlying the Puchack well field, no water from there has been withdrawn for public supply since 1998, when the U.S. Environmental Protection Agency (USEPA) added the area that contains the Puchack well field to the National Priorities List. As part of the USEPA's investigation of the Puchack Well Field Superfund site, the U.S. Geological Survey (USGS) conducted a study during 1997-2001 to (1) refine previous interpretations of the hydrostratigraphic framework, hydraulic gradients, and local directions of ground-water flow; (2) describe the chemistry of soils and saturated aquifer sediments; and (3) document the quality of ground water in the Potomac-Raritan-Magothy aquifer system in the area. The four major water-bearing units of the Potomac-Raritan-Magothy aquifer system-the Upper aquifer (mostly unsaturated in the study area), the Middle aquifer, the Intermediate Sand (a local but important unit), and the Lower aquifer-are separated by confining units. The confining units contain areas of cut and fill, resulting in permeable zones that permit water to pass through them. Pumping from the Puchack well field during the past 3 decades resulted in downward hydraulic gradients that moved contaminants into the Lower aquifer, in which the production wells are finished, and caused ground water to flow northeast, locally. A comparison of current (1997-2001) water levels near the site of the former pumping center with data from previous investigations indicates that, since pumping at the Puchack well field ceased, the dominant local ground-water flow direction is to the southeast, aligned with regional flow. Chromium concentrations were highest (8,010 micrograms per liter in 2000-01) in water from the Middle aquifer immediately downgradient from a possible source; the extent of this chromium plume is unknown but appears to be small. A second, unrelated, localized chromium plume also was identified in the Middle aquifer. The Intermediate Sand was found to contain an areally extensive plume of chromium-contaminated water, with concentrations up to 6,310 micrograms per liter in 2000-01, and another plume of about the same size, with concentrations up to 4,810 micrograms per liter in 2000-01, was identified in the Lower aquifer. The previous USGS investigation indicated the approximate extent of the combined plumes; the current delineation indicates that their locations have shifted slightly to the southeast since 1998. Concentrations of chromium in ground water decreased at some well locations by as much as 60 percent between sampling rounds in 1997-98 and 1999-2001. The decrease in chromium concentration at a given well could be the result of the chemical reduction of hexavalent chromium and precipitation of the resulting trivalent chromium, the sorption of hexavalent chromium to aquifer materials, or the physical movement of the plumes. Available data indicate that all three processes likely have affected concentrations. The distribution of hexavalent and total chromium in the soils and sediments of a possible source area indicates that some hexavalent chromium has undergone chemical reduction in the soils, but the degree to which this process takes place in the aquifer currently is not known. Nor is it known whether contaminated soils continue to contribute chromium to the aquifer system. Contamination by vola

Scientific Investigations Report↗
USGS2012

Contaminants in stream sediments from seven United States metropolitan areas: part I: distribution in relation to urbanization

Organic contaminants and trace elements were measured in bed sediments collected from streams in seven metropolitan study areas across the United States to assess concentrations in relation to urbanization. Polycyclic aromatic hydrocarbons, polychlorinated biphenyls, organochlorine pesticides, the pyrethroid insecticide bifenthrin, and several trace elements were significantly related to urbanization across study areas. Most contaminants (except bifenthrin, chromium, nickel) were significantly related to the total organic carbon (TOC) content of the sediments. Regression models explained 45–80 % of the variability in individual contaminant concentrations using degree of urbanization, sediment-TOC, and study-area indicator variables (which represent the combined influence of unknown factors, such as chemical use or release, that are not captured by available explanatory variables). The significance of one or more study-area indicator variables in all models indicates marked differences in contaminant levels among some study areas, even after accounting for the nationally modeled effects of urbanization and sediment-TOC. Mean probable effect concentration quotients (PECQs) were significantly related to urbanization. Trace elements were the major contributors to mean PECQs at undeveloped sites, whereas organic contaminants, especially bifenthrin, were the major contributors at highly urban sites. Pyrethroids, where detected, accounted for the largest share of the mean PECQ. Part 2 of this series (Kemble et al. 2012) evaluates sediment toxicity to amphipods and midge in relation to sediment chemistry.

Archives of Environmental Contamination and Toxico↗
USGS2018

An on-campus well field for hydrogeophysics education and undergraduate research

The emerging subdiscipline of hydrogeophysics is underdeveloped in undergraduate curricula relative to its importance in professional engineering/environmental practice. In 2001, the Bucknell Department of Geology initiated efforts to refocus an undergraduate geophysics course on near-surface geophysical methods for hydrologic, environmental, and engineering problems. In addition to offering students practical experience, treatment of hydrogeophysics provides important pedagogical opportunities. Field-based hydrogeophysics labs challenge students to integrate concepts from other geology courses, as well as from physics, math, and chemistry. We faced two challenges in revising our geophysics course: (1) access to wells for field exercises on borehole geophysics; and (2) the costs of acquiring and maintaining equipment. We pursued two strategies to solve these problems. First, we established an on-campus well field, which serves as a field laboratory for downhole and cross-hole experiments. Second, we incorporated field demonstrations and lectures by professional geoscientists, including alumni, into our courses. By adding field exercises to our syllabi and promoting undergraduate research, we are building a cutting-edge dataset that includes televiewer and standard wellbore logging, cross-hole tomography, and hydraulic-test data. Student-led analysis of these data has already provided valuable insights into the control of fractures on aquifer properties, and these observations are being combined with outcrop studies to place our results in a more regional context.

Pennsylvania↗
USGS2017

Contaminants of emerging concern in the Great Lakes Basin: A report on sediment, water, and fish tissue chemistry collected in 2010-2012

Despite being detected at low levels in surface waters and sediments across the United States, contaminants of emerging concern (CECs) in the Great Lakes Basin are not well characterized in terms of spatial and temporal occurrence. Additionally, although the detrimental effects of exposure to CECs on fish and wildlife have been documented for many CECs in laboratory studies, we do not adequately understand the implications of the presence of CECs in the environment. Based on limited studies using current environmentally relevant concentrations of chemicals, however, risks to fish and wildlife are evident. As a result, there is an increasing urgency to address data gaps that are vital to resource management decisions. The U.S. Fish and Wildlife Service, in collaboration with the U.S. Geological Survey, is leading a Great Lakes Basin-wide evaluation of CECs (CEC Project) with the objectives to (a) characterize the spatial and temporal distribution of CECs; (b) evaluate risks to fish and wildlife resources; and (c) develop tools to aid resource managers in detecting, averting, or minimizing the ecological consequences to fish and wildlife that are exposed to CECs. This report addresses objective (a) of the CEC Project, summarizing sediment and water chemistry data collected from 2010 to 2012 and fish liver tissue chemistry data collected in 2012; characterizes the sampling locations with respect to potential sources of CECs in the landscape; and provides an initial interpretation of the variation in CEC concentrations relative to the identified sources. Data collected during the first three years of our study, which included 12 sampling locations and analysis of 134 chemicals, indicate that contaminants were more frequently detected in sediment compared to water. Chemicals classified as alkyphenols, flavors/ fragrances, hormones, PAHs, and sterols had higher average detection frequencies in sediment compared to water, while the opposite was observed for pesticides, pharmaceuticals, and plasticizers/flame retardants. The St. Louis River and Maumee River sampling locations had the most CEC detections in water and sediment, relative to other sites, as well as the largest number of maximum detected concentrations across all sites in the Basin. No consistent temporal CEC occurrence patterns were observed at locations sampled multiple times each day. Most appearances and increases in chemical concentrations in sediments occurred at sites immediately downstream from wastewater treatment plants and at sites with predominantly developed land use. The location with the most observed appearances and increases was the St. Louis River. Perfluorinated compounds were commonly detected in fish liver tissues with detections in 100% of both benthic and pelagic species. The occurrence of these chemicals in liver tissue of benthic and pelagic species was generally similar. Abstract

Great Lakes Basin↗
USGS1996

Hazard ranking of contaminated sediments based on chemical analysis, laboratory toxicity tests, and benthic community composition: Prioritizing sites for remedial action

The U.S. Environmental Protection Agency (U.S. EPA) organized a research program to assess the extent of and possible methods for managing contaminated sediments. As part of this program, we developed a method by which multiple forms of information on sediment contamination (i.e., chemistry, laboratory toxicity, and benthic community composition) could be combined to rank the relative hazard to aquatic life of a series of sediment samples. The process that was developed incorporates chemistry and bioavailability into the ranking as toxic units in pore water based on U.S. EPA Ambient Water Quality Criteria (AWQC). Laboratory toxicity is incorporated into the ranking process as mean response relative to control response. Benthic community information is incorporated into the ranking process through the use of relative tolerance to pollution among benthic invertebrate taxa, from which the mean tolerance to pollution of the benthic community is calculated. The three resulting ranks are then averaged to produce a relative ranking of risk to aquatic life among sediment samples. Our results demonstrate that, as long as a moderate list of laboratory toxicity test results are included in the ranking process (i.e., tests from a fish, a zooplankter, a benthic invertebrate, a phytoplankter, and a microbe), the resultant rankings among samples does not significantly change with inclusion of more laboratory toxicity test results. Without any benthic community structure information, with only laboratory toxicity test results from Microtox, ® and with only a short list of chemicals, relative ranking among sites changes drastically. Our results demonstrate the general utility of the ranking process as one way of assessing the relative hazard among many sites when resource limitations necessitate prioritization of sites for remediation.

Journal of Great Lakes Research↗
USGS2003

Geoenvironmental Investigations of the Humboldt River Basin, Northern Nevada

Northern Nevada is one of the world's foremost regions of gold production. The Humboldt River Basin (HRB) covers 43,500 km2 in northern Nevada (Crompton, 1995), and it is home to approximately 18 active gold and silver mines (Driesner and Coyner, 2001) among at least 55 significant metallic mineral deposits (Long and others, 1998). Many of the gold mines are along the Carlin trend in the east-central portion of the HRB, and together they have produced 50 million ounces of gold from 1962 (when the Carlin mine first opened) through April 2002 (Nevada Mining Association, 2002). Mining is not new to the region, however. Beginning in 1849, mining has taken place in numerous districts that cover 39 percent of the land area in the HRB (Tingley, 1998). In addition to gold and silver, As, Ba, Cu, Fe, Hg, Li, Mn, Mo, Pb, S, Sb, V, W, Zn, and industrial commodities such as barite, limestone, fluorite, sand and gravel, gypsum, gemstones, pumice, zeolites, and building stone, have been extracted from the HRB (McFaul and others, 2000). All papers within this series of investigations can be found as lettered chapters of USGS Bulletin 2210, Geoenvironmental Investigations of the Humboldt River Basin, Northern Nevada. Each chapter is available separately online. The data and software utilized in this product (Chapter F) permit the user to view and analyze the geographic relationships among chemistry of stream sediments and surface waters, geology, and various cartographic base information such as but not limited to cities, county boundaries, and land ownership. Data for this product were compiled and or produced as part of a mineral and environmental assessment of the Humboldt River basin conducted by the U.S. Geological Survey between 1995 - 2000.

Bulletin↗