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At least 865 records · Page 48Linked to original sources
USGS2004

Chapter 8 Petrogenesis and mineralogic residence of selected elements in the meade peak phosphatic shale member of the permian phosphoria formation, Southeast Idaho

The Meade Peak Phosphatic Shale Member of the Permian Phosphoria Formation hosts the ore mined by the phosphate industry of southeast Idaho. It also hosts environmentally sensitive elements (ESE) such as Se, As, Hg, Ni, Cd, Zn, and Cr. Primary chemistry, elemental distribution patterns, and mineralogy within the Meade Peak were modified by element migration and possibly the introduction of elements. Fluids moved within the Meade Peak throughout its history, although the passage of fluids was highly variable in space and time, resulting in small domains of different rock chemistry and different mineralogy. Timing of major events affecting the Meade Peak and mineral habit are used to differentiate among detrital, diagenetic, epigenetic, and supergene mineral assemblages. Cross-cutting relationships among minerals are too rare to provide much paragenetic infor- mation. Carbonate fluorapatite (CFA) occurs in several forms, but dominantly as pelloids, some of which may have formed in situ during diagenesis. The other volumetrically signifi- cant form of CFA is interstitial cement that formed during diagenesis. Beginning during diagenesis and continuing intermittently, multiple generations of carbonate (dolomite and calcite) formed overgrowths and texturally complex carbonate cements. Movement and precipitation of silica followed a similar pattern. The ammonium feldspar buddingtonite, which generally rims orthoclase, also formed during diagenesis. Bacteria apparently played a significant role during diagenesis as well as during supergene processes, resulting in extreme fractionation of S isotopes and the possible bacterially mediated formation of minerals such as glauconite and sphalerite. Catagenesis, apparently culminating in oil generation, was the last significant diagenetic change. Thrusting accompanied by fluid (oil and brine) migration began during catagenesis in the Late Jurassic or Cretaceous and continued into the early Eocene. Fluorite ± carbonate ± barite± bitumen veins formed as a result of brittle deformation and accompanying fluid movement. This fracturing event may have been associated with a period of extension and normal faulting (Neogene to Holocene). Passage of the Yellowstone hot spot to the north of the area during the Neogene is marked by silicic domes and basaltic flows. The enrichment of Hg in fracture coatings might be the result of deposition from warm fluids associated with the emplacement of the silicic domes or a generally elevated, regional thermal gradient associated with the volcanism. Many of the fracture systems are still open and continue to provide fluid pathways that are the primary depositional sites for a wide variety of supergene minerals (such as Se, efflorescent salts) and element associations (such as Hg, Cd-S, Fe-Cr-O) in which many of the ESE are concentrated. Native Se is the most commonly identified host of Se in the studied samples. The largest concentration of Se occurs in open-fracture systems that cross-cut waste rock and ore units. The age(s) of native Se formation is not known; how- ever, the latest period of Se mobility is the present. Direct measurement of efflorescent “salts” forming on new mine faces indicate that several ESE, including both Se and Zn, are concentrated on the faces soon after they are exposed. Zinc is present as hydrous sulfates, but the residence of Se in these “salts” is unknown.

Idaho↗
USGS2010

Chemical and morphological comparison of erionite from Oregon, North Dakota, and Turkey

Erionite, a fibrous zeolite, occurs in pediment gravel deposits near Killdeer Mountain, North Dakota. Material from these pediment deposits has been excavated for use as roadbed throughout Dunn County, North Dakota. Erionite also occurs in the Cappadocian region of Turkey, where a link between malignant mesothelioma and inhalation of this mineral has been established. The U.S. Environmental Protection Agency (EPA), Region 8, requested that the U.S. Geological Survey (USGS) compare the chemistry and morphology of erionite collected from the Killdeer Mountains to those collected from villages in Turkey and from Rome, Oregon, which has also been linked to disease in animal studies.

Open-File Report↗
USGS1980

Intrusions and intrusive complexes in an ophiolite near San Luis Obispo; a chemical and petrologic study

The San Luis Obispo ophiolite is a sequence of mafic and ultramafic rocks that lie as a thrust-like slice on top of Franciscan melange in the southern California Coast Range. The ophiolite comprises the classic Steinmann Trinity of basal serpentinized ultramafic rocks overlain sequentially by spilitized pillow lavas and cherts. The ophiolite is intruded by numerous diabasic dikes and several large intrusive complexes that contain peridotite, gabbro, diabase and felsic rocks. Field relations indicate that this ophiolite originated as a sequence of submarine volcanic flows and breccia units extruded onto an ultramafic basement. Later the volcanic and ultramafic rocks were intruded along their contact by mafic magma that crystallized as a stratiform complex of cumulate peridotite and gabbro. Next, this stratiform complex was intruded by diorite and albite-granite (trondhjemite) sills, which may have been produced by partial melting of gabbros in the upper levels of the stratiform complex. Finally all earlier units were intruded by diabasic sills and dikes that probably were late feeders for the pre-existing volcanic unit. All the ophiolite rocks underwent subsequent highly localized brecciation, under greenschist-facies conditions, in which felsic rocks were incipiently melted by frictional heating. The host rocks and intrusions were metamorphosed at low temperature and the mafic rocks were altered by Na- and Si-metasomatism. Despite this pervasive alteration, evidences of the formational stages of the ophiolite are preserved in disequilibrium mineral assemblages, primarily within mafic and ultramafic rocks of the intrusive complexes. Whole-rock analyses of the ophiolite suite indicate that alteration has obscured but not obliterated the original chemical character of the mafic rocks. The ophiolite diabases and basalts contain up to 6 weight percent Na 2 0 and 58 percent Si0 2 , in contrast to normal Si0 2 contents of 50 percent or less and Na 2 0 contents of less than 3 percent for unaltered oceanic and continental tholeiite basalts. However, the low K 2 0 contents (less than 0.8 percent) of all units in the ophiolite suite indicate that these rocks are not part of an alkalic kindred, but rather are altered tholeiites. Compositions of relict amphibole and plagioclase in the mafic rocks indicate that the ophiolite formed in a high-temperature environment and the deep seated rocks were metamorphosed under amphibolite-facies conditions. A later change in the environmental conditions allowed subsequent low-temperature (greenschist facies) metamorphism and metasomatism. The structure and chemistry of the San Luis Obispo ophiolite support the hypothesis that this body may represent a fragment of oceanic crust and mantle. The volcanic rocks and the intrusive complexes probably formed at a mid-ocean ridge, where conditions of high heat-flow provided the requisite high-temperature environment and promoted the production of mafic magmas. The change to low-temperature conditions probably was due to inception or acceleration of crustal spreading at that portion of the ridge where this ophiolite formed. The nature of brecciation in the ophiolite indicates that the low-temperature environment also was one of greater tectonic disturbance, relative to conditions at the ridge. This tectonically active environment probably corresponds to an island arc where the ophiolite-bearing plate was subducted in an adjacent trench. The absence of a high-pressure mineral assemblage in the San Luis Obispo ophiolite suggests that this segment of ocean-crust and upper mantle was not buried in a subduction zone, but rather was rafted on top of subduction melange (Franciscan Formation) into its present position.

California↗
USGS2011

Groundwater chemistry near an impoundment for produced water, Powder River Basin, Wyoming, USA

The Powder River Basin is one of the largest producers of coal-bed natural gas (CBNG) in the United States. An important environmental concern in the Basin is the fate of the large amounts of groundwater extracted during CBNG production. Most of this produced water is disposed of in unlined surface impoundments. A 6-year study of groundwater flow and water chemistry at one impoundment, Skewed Reservoir, has produced the most detailed data set for any impoundment in the Basin. Data were collected from a network of 21 observation wells and three suction lysimeters. A groundwater mound formed atop bedrock within initially unsaturated, unconsolidated deposits underlying the reservoir. Heterogeneity in physical and chemical properties of sediments resulted in complex groundwater flow paths and highly variable groundwater chemistry. Sulfate, bicarbonate, sodium, and magnesium were the dominant ions in all areas, but substantial variability existed in relative concentrations; pH varied from less than 3 to more than 9, and total dissolved solids concentrations ranged from less than 5000 to greater than 100,000 mg/L. Selenium was a useful tracer of reservoir water; selenium concentrations exceeded 300 μg/L in samples obtained from 18 of the 24 sampling points. Groundwater travel time from the reservoir to a nearby alluvial aquifer (a linear distance of 177 m) was calculated at 474 days on the basis of selenium concentrations. The produced water is not the primary source of solutes in the groundwater. Naturally occurring salts and minerals within the unsaturated zone, dissolved and mobilized by infiltrating impoundment water, account for most of the solute mass in groundwater. Gypsum dissolution, cation-exchange, and pyrite oxidation appear to be important reactions. The complex geochemistry and groundwater flow paths at the study site underscore the difficulty in assessing effects of surface impoundments on water resources within the Powder River Basin.

Wyoming↗
USGS2017

Application of molluscan analyses to the reconstruction of past environmental conditions in estuaries

Molluscs possess a number of attributes that make them an excellent source of past environmental conditions in estuaries: they are common in estuarine environments; they typically have hard shells and are usually well preserved in sediments; they are relatively easy to detect in the environment; they have limited mobility as adults; they grow by incremental addition of layers to their shells; and they are found in all the major environments surrounding estuaries—terrestrial, freshwater, brackish, and marine waters. Analysis of molluscan assemblages can contribute information about past changes in sea level, climate, land use patterns, anthropogenic alterations, salinity, and other parameters of the benthic habitat and water chemistry within the estuary. High-resolution (from less than a day to annual) records of changes in environmental parameters can be obtained by analyzing the incremental growth layers in mollusc shells (sclerochronology). The shell layers retain information on changes in water temperature, salinity, seasonality, climate, river discharge, productivity, pollution and human activity. Isotopic analyses of mollusc shell growth layers can be problematic in estuaries where water temperatures and isotopic ratios can vary simultaneously; however, methods are being developed to overcome these problems. In addition to sclerochronology, molluscs are important to Holocene and Pleistocene estuarine palaeoenvironmental studies because of their use in the development of age models through radiocarbon dating, amino acid racemization, uranium-thorium series dating, and electron spin resonance (ESR) dating.

Book chapter↗
USGS2022

Integrated assessment of chemical and biological recovery after diversion and treatment of acid mine drainage in a Rocky Mountain stream

Responses of stream ecosystems to gradual reductions in metal loading following remediation or restoration activities have been well documented in the literature. However, much less is known about how these systems respond to the immediate or more rapid elimination of metal inputs. Construction of a water treatment plant on the North Fork of Clear Creek (NFCC; CO, USA), a US Environmental Protection Agency Superfund site, captured, diverted, and treated the two major point-source inputs of acid mine drainage (AMD) and provided an opportunity to investigate immediate improvements in water quality. We conducted a 9-year study that included intensive within- and among-year monitoring of receiving-stream chemistry and benthic communities before and after construction of the treatment plant. Results showed a 64%–86% decrease in metal concentrations within months at the most contaminated sites. Benthic communities responded with increased abundance and diversity, but downstream stations remained impaired relative to reference conditions, with significantly lower taxonomic richness represented by a few dominant taxa (i.e., Baetis sp., Hydropsyche sp., Simulium sp., Orthocladiinae). Elevated metal concentrations from apparent residual sources, and relatively high conductivity from contributing major ions not removed during the treatment process, are likely limiting downstream recovery. Our study demonstrates that direct AMD treatment can rapidly improve water quality and benefit aquatic life, but effectiveness is limited, in part, to the extent that inputs of metals are captured and treated. Consideration should also be given to the effects of elevated major ion concentrations from the treated effluent not removed during the lime treatment process. Continued chemical and biological monitoring will be needed to quantify the NFCC recovery trajectory and to inform future remediation strategies.

Colorado↗
USGS2015

Modeling and management of pit lake water chemistry 2: Case studies

Pit lakes, a common product of open pit mining techniques, may become long-term, post-mining environmental risks or long-term, post-mining water resources depending upon management decisions. This study reviews two published pit lake modeling studies and one pit lake monitoring program in order to increase the transparency of approaches used in pit lake prediction and management. The first model is a two-year limnological simulation of the existing Dexter pit lake, Nevada, USA that accurately modeled temperature profiles, salinity profiles, and turnover events observed between 1999 and 2000. The second model is a 55-year prediction of a future pit lake in the Martha Mine, New Zealand that identified the need for additional mitigation and evaluated potential effects of cost-effective mitigation options. The final study reviews eight years of monitoring data collected from the Berkeley pit lake, Montana, USA, from 2004 to 2012. This study identifies changes in the physical limnology and water quality of the pit lake that resulted from metal recovery operations, and highlights the value of monitoring programs in general. Whereas these pit lakes are different in many ways, the management tools discussed herein maximized the value and understanding of the post-mining resources.

Applied Geochemistry↗
USGS1999

Wetlands of the Prairie Pothole Region: Invertebrate species composition, ecology, and management

The Prairie Pothole Region (PPR) of the United States and Canada is a unique area where shallow depressions created by the scouring action of Pleistocene glaciation interact with mid-continental climate variations to create and maintain a variety of wetland classes. These wetlands possess unique environmental and biotic characteristics that add to the overall regional diversity and production of aquatic invertebrates and the vertebrate wildlife that depend upon them as food. Climatic extremes in the PPR have a profound and dynamic influence on wetland hydrology, hydroperiod, chemistry, and ultimately the biota. Available knowledge of aquatic invertebrates in the PPR suggests that diversity of invertebrates within each wetland class is low. Harsh environmental conditions range from frigid winter temperatures that freeze wetlands and their sediments to hot summer temperatures and drought conditions that create steep salinity gradients and seasonally dry habitats. Consequently, the invertebrate community is composed mostly of ecological generalists that possess the necessary adaptations to tolerate environmental extremes. In this review, we describe the highly dynamic nature of prairie pothole wetlands and suggest that invertebrate studies be evaluated within a conceptual framework that considers important hydrologic, chemical, and climatic events.

Book chapter↗
USGS2000

Ground-water microbiology and geochemistry

Up-to-date coverage and a unique, multidisciplinary approach The ongoing effort to protect our valuable ground-water resources necessarily involves scientists and engineers from many disciplines. Ground-Water Microbiology and Geochemistry, Second Edition is designed to bridge the historical lack of communication among these disciplines by detailing-in language that cuts across specialties-the impact of microorganisms and microbial processes on ground-water systems. Carefully revised to reflect the many recent discoveries that have been made in the field, the Second Edition begins with an overview of microbiology, ideal for hydrologists and others who may lack formal training in the field. These initial chapters systematically cover the kinds of microorganisms found in subsurface environments, focusing on their growth, metabolism, genetics, and ecology. The second part of the book offers a hydrologic perspective on how microbial processes affect ground-water geochemistry in pristine systems. It also introduces the different classes of ground-water systems, and gives an overview of techniques for sampling subsurface environments. Readers gain an understanding of biogeochemical cycling in ground-water systems-in coverage unique to this book-and how ground-water chemistry can be used to study microbial processes in aquifer systems. The final section of the book deals with the biodegradation of human-introduced contaminants in ground-water systems, with an up-to-date review of the physiology, biochemistry, and redox conditions that favor biodegradation processes. Ground-Water Microbiology and Geochemistry, Second Edition is important reading for geoscientists, hydrologists, and environmental engineers, as well as for water planners and lawyers involved in environmental issues. It also serves as a compelling text for upper-level undergraduate and graduate courses in ground-water chemistry.

Book↗
USGS2011

An evaluation of the relative quality of dike pools for benthic macroinvertebrates in the Lower Missouri River, USA

A habitat-based aquatic macroinvertebrate study was initiated in the Lower Missouri River to evaluate relative quality and biological condition of dike pool habitats. Water-quality and sediment-quality parameters and macroinvertebrate assemblage structure were measured from depositional substrates at 18 sites. Sediment porewater was analysed for ammonia, sulphide, pH and oxidation-reduction potential. Whole sediments were analysed for particle-size distribution, organic carbon and contaminants. Field water-quality parameters were measured at subsurface and at the sediment-water interface. Pool area adjacent and downstream from each dike was estimated from aerial photography. Macroinvertebrate biotic condition scores were determined by integrating the following indicator response metrics: % of Ephemeroptera (mayflies), % of Oligochaeta worms, Shannon Diversity Index and total taxa richness. Regression models were developed for predicting macroinvertebrate scores based on individual water-quality and sediment-quality variables and a water/sediment-quality score that integrated all variables. Macroinvertebrate scores generated significant determination coefficients with dike pool area ( R 2 =0.56), oxidation–reduction potential ( R 2 =0.81) and water/sediment-quality score ( R 2 =0.71). Dissolved oxygen saturation, oxidation-reduction potential and total ammonia in sediment porewater were most important in explaining variation in macroinvertebrate scores. The best two-variable regression models included dike pool size + the water/sediment-quality score ( R 2 =0.84) and dike pool size + oxidation-reduction potential ( R 2 =0.93). Results indicate that dike pool size and chemistry of sediments and overlying water can be used to evaluate dike pool quality and identify environmental conditions necessary for optimizing diversity and productivity of important aquatic macroinvertebrates. A combination of these variables could be utilized for measuring the success of habitat enhancement activities currently being implemented in this system.

Iowa;Nebraska;Missouri;Kansas↗
USGS2011

Application of neural networks to prediction of fish diversity and salmonid production in the Lake Ontario basin

Diversity and fish productivity are important measures of the health and status of aquatic systems. Being able to predict the values of these indices as a function of environmental variables would be valuable to management. Diversity and productivity have been related to environmental conditions by multiple linear regression and discriminant analysis, but such methods have several shortcomings. In an effort to predict fish species diversity and estimate salmonid production for streams in the eastern basin of Lake Ontario, I constructed neural networks and trained them on a data set containing abiotic information and either fish diversity or juvenile salmonid abundance. Twenty percent of the original data were retained as a test data set and used in the training. The ability to extend these neural networks to conditions throughout the streams was tested with data not involved in the network training. The resulting neural networks were able to predict the number of salmonids with more than 84% accuracy and diversity with more than 73% accuracy, which was far superior to the performance of multiple regression. The networks also identified the environmental variables with the greatest predictive power, namely, those describing water movement, stream size, and water chemistry. Thirteen input variables were used to predict diversity and 17 to predict salmonid abundance.

Transactions of the American Fisheries Society↗
USGS2009

Simulation of Groundwater-Level and Salinity Changes in the Eastern Shore, Virginia

Groundwater-level and salinity changes have been simulated with a groundwater model developed and calibrated for the Eastern Shore of Virginia. The Eastern Shore is the southern part of the Delmarva Peninsula that is occupied by Accomack and Northampton Counties in Virginia. Groundwater is the sole source of freshwater to the Eastern Shore, and demands for water have been increasing from domestic, industrial, agricultural, and public-supply sectors of the economy. Thus, it is important that the groundwater supply be protected from overextraction and seawater intrusion. The best way for water managers to use all of the information available is usually to compile this information into a numerical model that can simulate the response of the system to current and future stresses. A detailed description of the geology, hydrogeology, and historical groundwater extractions was compiled and entered into the numerical model. The hydrogeologic framework is composed of a surficial aquifer under unconfined conditions, a set of three aquifers and associated overlying confining units under confined conditions (the upper, middle, and lower Yorktown-Eastover Formation), and an underlying confining unit (the St. Marys Formation). An estimate of the location and depths of two major paleochannels was also included in the framework of the model. Total withdrawals from industrial, commercial, public-supply, and some agricultural wells were compiled from the period 1900 through 2003. Reported pumpage from these sources increased dramatically during the 1960s and 70s, up to currently about 4 million gallons per day. Domestic withdrawals were estimated on the basis of population census districts and were assigned spatially to the model on the assumption that domestic users are located close to roads. A numerical model was created using the U.S. Geological Survey (USGS) code SEAWAT to simulate both water levels and concentrations of chloride (representing salinity). The model was calibrated using 605 predevelopment and transient water-level observations that are associated predominantly with 20 observation nests of wells sited across the study area. Sampling for groundwater chemistry at these sites revealed that chloride has not increased significantly in the last 20 years. Environmental tracers in the samples also indicated that the water in the surficial aquifer is typically years to decades old, whereas water in the confined aquifers is typically centuries to millennia old. The calibration procedure yielded distributions of hydraulic conductivity and storage coefficients of the aquifers and confining units that are based on 21 pilot points, but vary smoothly across the study area. The estimated values are consistent with other measurements of these properties measured previously on cores and during hydraulic tests at various well fields. Simulations performed with the model demonstrated that the calibrated model can reproduce the observed historical water levels fairly well (R2 = 0.93). The chloride concentrations were also simulated, but a match with chloride concentrations was more difficult to achieve (R2 = 0.16) because of the lack of sufficient data and the unknown exact behavior of the entire transition zone in the millennia leading up to the present day. Future pumping scenarios were simulated through 2050, with pumping set to either 2003 rates or total permitted withdrawal rates. Water levels in 2050 are predicted to be lower than current levels by a few feet where stresses are currently heaviest but potentially by tens of feet if total permitted withdrawals are extracted at current low-stressed sites. Simulations of chloride concentrations through 2050 revealed some potential for seawater intrusion in the areas of Cape Charles, Chincoteague, east of the town of Exmore, and east of the town of Accomac, but precise estimates of concentration increases are highly uncertain. Simulation results were also used to estimate that the down

Scientific Investigations Report↗
USGS2020

Characterization of water-quality and bed-sediment conditions in Currituck Sound, North Carolina, prior to the Mid-Currituck Bridge construction, 2011–18

The North Carolina Turnpike Authority plans to improve transportation in the Currituck Sound area by constructing a two-lane bridge—the Mid-Currituck Bridge—across Currituck Sound from the mainland to the Outer Banks, North Carolina. The results of the final environmental impact statement for the project indicate potential water-quality and habitat effects for Currituck Sound associated with the bridge and roadway improvements. The primary objective of this study is to characterize water-quality conditions and bed-sediment chemistry in the vicinity of the planned Mid-Currituck Bridge, providing a baseline for evaluating the potential effects of bridge construction and bridge deck runoff on environmental conditions in Currituck Sound. From August 2011 through January 2018, water-quality and bed-sediment samples were collected from five sampling stations along the planned bridge alignment. Samples were analyzed for numerous characteristics, including physical properties and constituents that are associated with bridge deck stormwater runoff and are important to estuarine waters. The analyzed characteristics included dissolved oxygen, pH, specific conductance, turbidity, suspended solids, metals, nutrients, semi-volatile organic compounds, bacteria, chlorophyll a, cyanotoxins, and phytoplankton abundance. The most common constituents with concentrations above applicable State and Federal water-quality thresholds included chlorophyll a, pH, turbidity, Enterococci, and pentachlorophenol. Few bed-sediment samples had constituent concentrations that exceeded applicable sediment-quality guidelines. Results indicated that water sampled along the planned bridge alignment was well mixed vertically and horizontally but varied temporally. Seasonal changes in water quality best explained the variations in water-quality conditions in Currituck Sound during the study. Wind conditions also influenced water levels and water-quality conditions. Turbidity and concentrations of particle-associated constituents tended to be higher when water levels were lower, possibly reflecting the increased resuspension of bottom materials from wind-driven wave action.

North Carolina↗
USGS2006

Analysis of environmental variation in a Great Plains reservoir using principal components analysis and geographic information systems

We present a method for spatial interpretation of environmental variation in a reservoir that integrates principal components analysis (PCA) of environmental data with geographic information systems (GIS). To illustrate our method, we used data from a Great Plains reservoir (Skiatook Lake, Oklahoma) with longitudinal variation in physicochemical conditions. We measured 18 physicochemical features, mapped them using GIS, and then calculated and interpreted four principal components. Principal component 1 (PC1) was readily interpreted as longitudinal variation in water chemistry, but the other principal components (PC2-4) were difficult to interpret. Site scores for PC1-4 were calculated in GIS by summing weighted overlays of the 18 measured environmental variables, with the factor loadings from the PCA as the weights. PC1-4 were then ordered into a landscape hierarchy, an emergent property of this technique, which enabled their interpretation. PC1 was interpreted as a reservoir scale change in water chemistry, PC2 was a microhabitat variable of rip-rap substrate, PC3 identified coves/embayments and PC4 consisted of shoreline microhabitats related to slope. The use of GIS improved our ability to interpret the more obscure principal components (PC2-4), which made the spatial variability of the reservoir environment more apparent. This method is applicable to a variety of aquatic systems, can be accomplished using commercially available software programs, and allows for improved interpretation of the geographic environmental variability of a system compared to using typical PCA plots. ?? Copyright by the North American Lake Management Society 2006.

Lake and Reservoir Management↗
USGS1988

Runoff for selected sites in Shenandoah National Park, Virginia, July 18, 1981, through July 17, 1982

Estimates of runoff for 56 sites within the Shenandoah National Park were made by the U.S. Geological Survey for the Direct/Delayed Response Project that is being conducted by the U.S. Environmental Protection Agency. The purpose of that project is to determine the long-term effects of acidic deposition on surface-water chemistry. Runoff was estimated for the period July 18,1981, through July 17,1982 during which periodic water-quality samples were collected for a study by the U.S. Geological Survey to determine the sensitivity of the area to the current input of acid deposition. The runoff values and waterquality samples will be used by the U.S. Environmental Protection Agency (EPA) to determine chemical budgets for 56 watersheds in the Park. The runoff estimates were determined by a graphical-correlation procedure. Six discharge measurements at each site were made when waterquality samples were collected; these were then correlated with the concurrent recorded discharges at one of 13 nearby streamflow-gaging stations. The mean discharge at the gaging station for the subject period was transferred through the relation line to estimate the mean discharge and runoff at the waterquality sampling site. The runoff estimates during the study period ranged from 10.9 to 38.7 inches. The accuracy of the method was evaluated by treating 13 nearby gaging stations as if they were water-quality sampling sites. A comparison of estimated and recorded runoff for the same period showed differences ranging from 28.2 to 49.5 percent, with an absolute average of 14.7 percent.

Virginia↗
USGS2002

Determination of the total oxygen isotopic composition of nitrate and the calibration of a Δ17Ο nitrate reference material

A thermal decomposition method was developed and tested for the simultaneous determination of δ 18 O and δ 17 Ο in nitrate. The thermal decomposition of AgNO 3 allows for the rapid and accurate determination of 18 O/ 16 O and 17 O/ 16 O isotopic ratios with a precision of ±1.5‰ for δ 18 O and ±0.11‰ for Δ 17 Ο (Δ 17 Ο = δ 17 Ο − 0.52 × δ 18 O). The international nitrate isotope reference material IAEA-NO3 yielded a δ 18 O value of +23.6‰ and Δ 17 Ο of −0.2‰, consistent with normal terrestrial mass-dependent isotopic ratios. In contrast, a large sample of NaNO 3 from the Atacama Desert, Chile, was found to have Δ 17 Ο = 21.56 ± 0.11‰ and δ 18 O = 54.9 ± 1.5‰, demonstrating a substantial mass-independent isotopic composition consistent with the proposed atmospheric origin of the desert nitrate. It is suggested that this sample (designated USGS-35) can be used to generate other gases (CO 2 , CO, N 2 O, O 2 ) with the same Δ 17 Ο to serve as measurement references for a variety of applications involving mass-independent isotopic compositions in environmental studies.

Analytical Chemistry↗
USGS2015

Characteristics and environmental aspects of slag: a review

Slag is a waste product from the pyrometallurgical processing of various ores. Based on over 150 published studies, this paper provides an overview of mineralogical and geochemical characteristics of different types of slag and their environmental consequences, particularly from the release of potentially toxic elements to water. This chapter reviews the characteristics of both ferrous (steel and blast furnace Fe) and non-ferrous (Ag, Cu, Ni, Pb, Sn, Zn) slag. Interest in slag has been increasing steadily as large volumes, on the order of hundreds of millions of tonnes, are produced annually worldwide. Research on slag generally focuses on potential environmental issues related to the weathering of slag dumps or on its utility as a construction material or reprocessing for secondary metal recovery. The chemistry and mineralogy of slag depend on the metallurgical processes that create the material and will influence its fate as waste or as a reusable product. The composition of ferrous slag is dominated by Ca and Si. Steel slag may contain significant Fe, whereas Mg and Al may be significant in Fe slag. Calcium-rich olivine-group silicates, melilite-group silicates that contain Al or Mg, Ca-rich glass, and oxides are the most commonly reported major phases in ferrous slag. Calcite and trace amounts of a variety of sulfides, intermetallic compounds, and pure metals are typically also present. The composition of non-ferrous slag, most commonly from base-metal production, is dominated by Fe and Si with significant but lesser amounts of Al and Ca. Silicates in the olivine, pyroxene, and melilite groups, as well as glass, spinels, and SiO 2 (i.e., quartz and other polymorphs) are commonly found in non-ferrous slag. Sulfides and intermetallic compounds are less abundant than the silicates and oxides. The concentrations of some elements exceed generic USEPA soil screening levels for human contact based on multiple exposure pathways; these elements include Al, Cr, Cu, Fe, Mn, Pb, and Zn based on bulk chemical composition. Each slag type usually contains a specific suite of elements that may be of environmental concern. In general, non-ferrous slag may have a higher potential to negatively impact the environment compared to ferrous slag, and is thus a less attractive material for reuse, based on trace element chemistry, principally for base metals. However, the amount of elements released into the environment is not always consistent with bulk chemical composition. Many types of leaching tests have been used to help predict slag’s long-term environmental behavior. Overall, ferrous slags produce an alkaline leachate due to the dissolution of Ca oxides and silicates derived from compounds originally added as fluxing agents, such as lime. Ferrous slag leachate is commonly less metal-rich than leachate from non-ferrous slag generated during base metal extraction; the latter leachate may even be acidic due to the oxidation of sulfides. Because of its characteristics, ferrous slag is commonly used for construction and environmental applications, whereas both non-ferrous and ferrous slag may be reprocessed for secondary metal recovery. Both types of slag have been a source of some environmental contamination. Research into the environmental aspects of slag will continue to be an important topic whether the goal is its reuse, recycling, or remediation.

Applied Geochemistry↗
USGS2012

Variability in stream chemistry in relation to urban development and biological condition in seven metropolitan areas of the United States, 1999-2004

Beginning in 1999, the U.S. Geological Survey National Water Quality Assessment Program investigated the effects of urban development on stream ecosystems in nine metropolitan study areas across the United States. In seven of these study areas, stream-chemistry samples were collected every other month for 1 year at 6 to 10 sites. Within a study area, the sites collectively represented a gradient of urban development from minimally to highly developed watersheds, based on the percentage of urban land cover; depending on study area, the land cover before urban development was either forested or agricultural. The stream-chemistry factors measured in the samples were total nitrogen, total phosphorus, chloride, and pesticide toxicity. These data were used to characterize the stream-chemistry factors in four ways (hereafter referred to as characterizations)—seasonal high-flow value, seasonal low-flow value, the median value (representing a single integrated value of the factor over the year), and the standard deviation of values (representing the variation of the factor over the year). Aquatic macroinvertebrate communities were sampled at each site to infer the biological condition of the stream based on the relative sensitivity of the community to environmental stressors. A Spearman correlation analysis was used to evaluate relations between (1) urban development and each characterization of the stream-chemistry factors and (2) the biological condition of a stream and the different characterizations of chloride and pesticide toxicity. Overall, the study areas where the land cover before urban development was primarily forested had a greater number of moderate and strong relations compared with the study areas where the land cover before urban development was primarily agriculture; this was true when urban development was correlated with the stream-chemistry factors (except chloride) and when chloride and pesticide toxicity was correlated with the biological condition. Except for primarily phosphorus in two study areas, stream-chemistry factors generally increased with urban development, and among the different characterizations, the median value typically indicated the strongest relations. The variation in stream-chemistry factors throughout the year generally increased with urban development, indicating that water quality became less consistent as watersheds were developed. In study areas with high annual snow fall, the variation in chloride concentrations throughout the year was particularly strongly related to urban development, likely a result of road salt applications during the winter. The relations of the biological condition to chloride and pesticide toxicity were calculated irrespective of urban development, but the overall results indicated that the relations were still stronger in the study areas that had been forested before urban development. The weaker relations in the study areas that had been agricultural before urban development were likely the results of biological communities having been degraded from agricultural practices in the watersheds. Collectively, these results indicated that, compared with sampling a stream at a single point in time, sampling at regular intervals during a year may provide a more representative measure of water quality, especially in the areas of high urban development where water quality fluctuated more widely between samples. Furthermore, the use of "integrated" values of stream chemistry factors may be more appropriate when assessing relations to the biological condition of a stream because the taxa composition of a biological community typically reflects the water-quality conditions over time.

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