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At least 1,171 records · Page 65Linked to original sources
USGS2004

Fish and Aquatic Invertebrate Communities in Waterways, and Contaminants in Fish, at the Barataria Preserve of Jean Lafitte National Historical Park and Preserve, Louisiana, 1999-2000

Fish and aquatic invertebrate communities in waterways of the Barataria Preserve of Jean Lafitte National Historical Park and Preserve, Louisiana, were surveyed from 1999 to 2000. An inventory of fish in the Barataria Preserve was established, and concentrations of selected organochlorine pesticides, polychlorinated biphenyls, and trace elements; iron; and manganese in fish tissue for selected species were determined. The fish and aquatic invertebrate sampling completed for this study indicated that abundant and diverse communities are present in the Barataria Preserve. Thirty-two species of fish were identified in the Barataria Preserve during this survey. The total number of species identified in a single sampling ranged from 20 to 26. Most of the fish sampled are designated as intermediate in their tolerance to poor water quality. Three species of fish designated as tolerant (common carp, Cyprinus carpio; golden shiner, Notemigonus crysoleucas; and yellow bullhead, Ameiurus natalis), and one as intolerant (lake chubsucker, Erymizon sucetta), were identified. In November 1999, the average total weight of all fish collected by boat-mounted electroshocker from a single site was about 35,000 grams; in May and July 1999, the average total weight was between 9,000 and 10,000 grams. The contribution of spotted gar (Lepisosteus oculatus) to the total weight of the fish averaged between 38 and 41 percent among the three sample periods. Members of the sunfish family (Centrarchidae) contributed between 18 and 28 percent of the total weight. For each sampling period, 60 to 83 percent of the total weight from the sunfish family was contributed by bluegill (Lepomis macrochirus) and largemouth bass (Micropterus salmoides). Aquatic invertebrates were sampled at three sites. Most aquatic invertebrates identified were freshwater species, but some were brackish-water and marine species. About 234,000 organisms were identified and enumerated from the richest-targeted habitat (RTH, floating rafts of aquatic plants). Individuals from 84 genera belonging to 51 families were identified. Diptera (true flies) was the most diverse group. Malacostraca (crustaceans), especially Amphipoda (scuds and sideswimmers), were the most abundant (36 percent). Total abundance and taxa richness of aquatic invertebrates were comparable during the March and July sampling in 1999, but were lower in samples collected from the same habitat at all three sites in April 2000. About 106 individuals were identified and enumerated from the depositional-targeted habitat (DTH, bottom material). Individuals from 7 genera belonging to 9 families were identified. Diptera was the most diverse group, and Annelida, especially tubificid worms, were the most abundant organisms identified (52 percent). Total abundance and composition of aquatic invertebrate communities differed between RTH and DTH at all three sites in April 2000. Organic compounds in whole fish, and trace elements, iron, and manganese in fillets, were analyzed in bowfin (Amia calva), bluegill (Lepomis macrochirus), largemouth bass (Micropterus salmoides), and common carp (Cyprinus carpio). Organic compounds were not detected. Mercury was detected in fillets of all four species. Highest concentrations of mercury were detected in fillets from bowfin and largemouth bass. Mercury concentrations increased with increasing weight in the three predatory fish species (bowfin, bluegill, and largemouth bass), but were much lower, relative to weight, in the omnivore, common carp. Chromium concentrations were detected in tissue of the two larger fish, bowfin and common carp. Cadmium and lead were not detected in any samples. Mercury concentrations for larger predatory fish caught in Preserve waterways may be a concern if the fish are frequently consumed by humans. The process of mercury accumulation appears to be natural, and not related to a local source problem. Mercury concentrations in comparable fish tissue at

Scientific Investigations Report↗
USGS2016

Physical, chemical, and biological characteristics of selected headwater streams along the Allegheny Front, Blair County, Pennsylvania, July 2011–September 2013

The Altoona Water Authority (AWA) obtains all of its water supply from headwater streams that drain western Blair County, an area underlain in part by black shale of the Marcellus Formation. Development of the shale-gas reservoirs will require new access roads, stream crossing, drill-pad construction, and pipeline installation, activities that have the potential to alter existing stream channel morphology, increase runoff and sediment supply, alter streamwater chemistry, and affect aquatic habitat. The U.S. Geological Survey, in cooperation with Altoona Water Authority and Blair County Conservation District, investigated the water quality of 12 headwater streams and biotic health of 10 headwater streams. Channel morphology was characterized at 10 of 12 stream sites using 500-foot (minimum) longitudinal profiles, four cross-sections each, and pebble counts. Channel slopes ranged from 0.008 in Poplar Run near Newry to 0.045 in Mill Run. In general, streams draining watersheds of 5 square miles or less and at higher elevation had the steepest slopes. On the basis of the median particle size, determined during pebble counts, the streambed substrate can be characterized as cobble (Mill Run, Bells Gap Run, Tipton Run, and Sink Run), a mix of gravel and cobble (South Poplar Run, Dry Gap Run, Glenwhite Run, Sugar Run, Blair Gap Run), and gravel (Poplar Run, Newry). Daily mean values of gage height were determined, and continuous (30-minute interval) data consisting of specific conductance and water temperature were collected, at four sites; each site showed typical seasonal fluctuations and the effects of precipitation. Streamflow affected discrete water-quality. Dissolved oxygen always increased with increased streamflow. Most cations (including barium and strontium), along with pH, specific conductance, and total dissolved solids, decreased with greater streamflow, reflecting the dilution effect of moderately acidic surface runoff and precipitation on groundwater discharge (base flow) into the stream channels. Concentrations of trace elements varied by constituent and streamflow. On the basis of the results of water-quality analyses for the selected constituents, the water quality in 9 of the 12 streams can be considered fair or attaining with no measured constituent exceeding a U.S. Environmental Protection Agency maximum or secondary contaminant level. Abandoned mine drainage (AMD) affects Glenwhite Run, Blair Gap Run, and Sugar Run. For Sugar Run, the AMD is reflected in the elevated iron concentration (greater than 300 micrograms per liter). Manganese concentrations greater than 50 micrograms per liter were measured in Glenwhite Run, Sugar Run, and Blair Gap Run. A mixing curve based upon chloride/bromide ratios for two end points—precipitation and deicing salts—indicate that deicing salt is migrating to the streams. A similar curve representative of late-emerging flowback water from Marcellus gas wells indicated that the surface-water samples had not been influenced by such brines. On the basis of the concentration of major ions, the streams in the study area generally had mixed cation and anion compositions. Calcium is the dominant cation in one stream. Carbonate and bicarbonate are the dominant anions for two streams, and sulfate is dominant in three streams. The remaining six streams do not have a dominant ion. Biotic health was characterized at 10 of 12 stream sites; the two sites excluded were established late in the study period (May 2013) for refinement of water quality in the headwaters of Poplar Run and the location of Marcellus Formation gas wells. On the basis of the Maryland Index of Biotic Integrity (MdIBI) for fish assemblages, 8 of 10 streams can be considered in fair health. Tipton Run had the highest MdIBI score (3.75) and the greatest number of native species. South Poplar Run had the lowest MdIBI score (1.75); pollution tolerant blacknose dace was dominant. On the basis of the Pennsylvania Department of Environmental Protection macroinvertebrate index of biotic integrity, 9 of 10 streams were characterized as attaining, with scores as high as 88.9 at Tipton Run. Only Sugar Run was characterized as impaired, with a score of 40.4.

Pennsylvania↗
USGS2021

General water-quality conditions, long-term trends, and network analysis at selected sites within the Ambient Water-Quality Monitoring Network in Missouri, water years 1993–2017

The U.S. Geological Survey, in cooperation with the Missouri Department of Natural Resources, collects data pertaining to the surface-water resources of Missouri. Established in 1964, the Ambient Water-Quality Monitoring Network (AWQMN) consisted of 69 sites in 2017. Two additional sites from the National Water-Quality Program are included with the AWQMN sites for the analyses in this report. The sites are sampled typically from 2 to 12 times per year for physical properties, total suspended solids, nutrients, fecal indicator bacteria, and trace elements. The period of analysis for this study was from 1993 through 2017 and data analysis included 71 sites and 15 water-quality constituents plus discharge. Data analysis involved retrieving the data, conditioning the data for analysis, analyzing the data for trends, and analyzing the monitoring network to determine if potential data gaps or data redundancies exist in the network. Results from these analyses can be used to help manage the monitoring network into the future. Water-quality data were analyzed using several software packages to provide graphical and statistical information for interpretation of trends in the data at selected sites. Discharge data at selected sites were analyzed to determine the general trends during the analysis period and how the water-quality samples represented the range of daily mean discharges at each site. Water-quality data also were analyzed at selected sites to determine the relative sensitivity of selected sites and constituents to changes in data collection frequency. Trend analysis at selected sites using a simulated reduction in sampling frequency was completed to compare to trends obtained using monthly data to determine the potential degradation in the ability of determining trends from a reduced sampling frequency. The viability of using estimated discharge to evaluate long-term trends for sites with no continuous discharge was investigated. Data from sites were statistically compared in groups to determine the relative similarity (or difference) between sites for each water-quality constituent to identify potentially redundant sites in the monitoring network. Discharge-weighted long-term trends during 1993 through 2017 were analyzed for 15 water-quality constituents at 58 sites and results indicated there were significant single- or two-period trends in about 17 percent of the analyses. Some trends indicated improvement and some trends indicated deterioration of the general water quality at some sites in the AWQMN. No trend was indicated in about 31 percent of the analyses. The constituents pH, specific conductance, and total phosphorus showed the most frequent significant trends, and each of the 15 constituents examined had a significant trend at one or more sites. A total of 42 sites indicated at least 1 constituent with a significant single- or two-period trend, and 10 sites indicated 6 or more significant trends. Potential data gaps identified for computing discharge-weighted long-term trends in the monitoring network included the lack of collection of continuous discharge at 23 sites, insufficient sampling frequency for some constituents (dissolved chloride and total and dissolved lead and zinc) at some sites, insufficient temporal sample distribution (lack of at least one sample in each season per year) at some sites, and insufficient sampling frequency for some highly censored constituents (nutrients and total and dissolved lead and zinc) at some sites. Potential data gaps based on site spatial distribution were identified in 7 basins greater than 800 square miles. Potential site redundancies were identified in 4 basins that had an area greater than 500 square miles with a site density greater than 2 sites per 1,000 square miles. Potential site redundancies also were identified for nine site pairs by observing statistical similarities in the constituent data distributions. Sampling frequency was investigated to determine if reducing the sampling frequency of select constituents could provide a statistically similar data distribution. At 28 of 71 sites, 11 constituents had sufficient data collection frequency (approximately monthly) to allow for the creation of simulated datasets of various reduced data collection frequency. For the selected monitoring network sites analyzed, the data distribution of a simulated sampling frequency of four times per year or greater, roughly evenly distributed over the year, was not significantly different than the data distribution of the original monthly sampling frequency. Sites analyzed using varying simulated sampling frequencies tended to be more sensitive to sampling frequency changes if they were in basins classified as large or very large size and tended to be least sensitive in basins classified as small and medium size in the Ozark Plateaus Province. Simulated reduced frequency sampling analysis indicated that the constituents and measurements most sensitive to changes in sampling frequencies were water temperature, dissolved oxygen, discharge, and dissolved nitrate, and least sensitive were pH, total suspended solids, dissolved phosphorus, and total phosphorus. Discharge-weighted long-term trend analysis was repeated at 22 sites for 11 constituents using a simulated quarterly sampling frequency, and matched about 46 percent of the significant single-period trends identified using monthly data and about 65 percent of the analyses that indicated no trend using the monthly data.

Missouri↗
USGS1996

Water-quality assessment of the Rio Grande Valley, Colorado, New Mexico, and Texas: Shallow ground-water quality of a land-use area in the San Luis Valley, south-central Colorado, 1993

This report describes the quality of shallow ground water in an agricultural area in the San Luis Valley, Colorado, and discusses how natural and human factors affect the quality of shallow ground water. Thirty-five wells were installed, and water samples were collected from these wells and analyzed for selected dissolved common constituents, nutrients, trace elements, radionuclides, and synthetic organic compounds. The San Luis Valley is a high intermontane valley that is partially drained by the Rio Grande. The San Luis Valley land-use study area was limited to a part of the valley where the depth to water is generally less than 25 feet. The area where the 35 monitor wells were installed was further limited to the part of the study area where center-pivot overhead sprinklers are used to irrigate crops. Precipitation, runoff from adjacent mountainous areas, and ground-water inflow from the adjacent mountainous areas are the main sources of water to the aquifers in the San Luis Valley. Discharge of water from the shallow, unconfined aquifer in the valley is mainly from evapotranspiration. The dominant land use in the San Luis Valley is agriculture, although nonirrigated land and residential land are interspersed with agricultural land. Alfalfa, native hay, barley, wheat, potatoes, and other vegetables are the main crops. Dissolved-solids concentrations in shallow ground water sampled ranged from 75 to 1,960 milligrams per liter. The largest median concentration of cations was for calcium, and the largest median concentration of anions was for bicarbonate in shallow ground water in the San Luis Valley. Calcium concentrations ranged from 7.5 to 300 milligrams per liter, and bicarbonate concentrations ranged from 28 to 451 milligrams per liter. Nitrite plus nitrate concentrations ranged from less than 0.1 to 58 milligrams per liter as N; water from 11 wells had nitrite plus nitrate concentrations greater than 10 milligrams per liter as N. With the exception of the following trace elements--aluminum, barium, iron, manganese, molybdenum, and uranium--the concentrations of trace elements were less than 10 micrograms per liter in 90 percent of the samples. All trace-element concentrations measured were below the maximum contaminant levels set by the U.S. Environmental Protection Agency. Five samples exceeded the proposed maximum contaminant level of 0.02 milligram per liter for uranium. All samples collected exceeded the proposed maximum contaminant level for radon-222. The volatile organic compound methyltertbutylether was detected in one sample at a concentration of 0.6 microgram per liter. Of the pesticides analyzed for, one or more were detected in water from 5 of the 35 wells sampled. Metribuzin was the most commonly detected pesticide and was detected in water from three wells at concentrations ranging from an estimated 0.005 to 0.017 microgram per liter. Metolachlor (detected in one sample at a concentration of 0.072 microgram per liter), prometon (detected in one sample at a concentration of 0.01 microgram per liter), and p,p'-DDE (detected in one sample at an estimated concentration of 0.002 microgram per liter) were the other pesticides detected. The U.S. Environmental Protection Agency lifetime health advisory for metolachlor, metribuzin, and prometon is 100 micrograms per liter, which is much larger than the concentrations measured in the shallow ground water sampled for this study. The elevated nitrite plus nitrate concentrations in shallow ground water are indicative of leaching of fertilizers from the land surface. This conclusion is consistent with conclusions made in other investigations of the San Luis Valley.

Colorado↗
USGS2008

Ground-water quality data in the San Fernando-San Gabriel study unit, 2005— Results from the California GAMA program

Ground-water quality in the approximately 460 square mile San Fernando-San Gabriel study unit (SFSG) was investigated between May and July 2005 as part of the Priority Basin Assessment Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basin Assessment Project was developed in response to the Groundwater Quality Monitoring Act of 2001 and is being conducted by the U.S. Geological Survey (USGS) in cooperation with the California State Water Resources Control Board (SWRCB). The San Fernando-San Gabriel study was designed to provide a spatially unbiased assessment of raw ground-water quality within SFSG, as well as a statistically consistent basis for comparing water quality throughout California. Samples were collected from 52 wells in Los Angeles County. Thirty-five of the wells were selected using a spatially distributed, randomized grid-based method to provide statistical representation of the study area (grid wells), and seventeen wells were selected to aid in the evaluation of specific water-quality issues or changes in water chemistry along a historic ground-water flow path (understanding wells). The ground-water samples were analyzed for a large number of synthetic organic constituents [volatile organic compounds (VOCs), pesticides and pesticide degradates], constituents of special interest [perchlorate, N-nitrosodimethylamine (NDMA), 1,2,3-trichloropropane (1,2,3-TCP), and 1,4-dioxane], naturally occurring inorganic constituents (nutrients, major and minor ions, and trace elements), radioactive constituents, and microbial indicators. Naturally occurring isotopes (tritium, and carbon-14, and stable isotopes of hydrogen, oxygen, and carbon), and dissolved noble gases also were measured to help identify the source and age of the sampled ground water. Quality-control samples (blanks, replicates, samples for matrix spikes) were collected at approximately one-fifth (11 of 52) of the wells, and the results for these samples were used to evaluate the quality of the data for the ground-water samples. Assessment of the quality-control results showed that the data had very little bias or variability and resulted in censoring of less than 0.7 percent (32 of 4,484 measurements) of the data collected for ground-water samples. This study did not attempt to evaluate the quality of water delivered to consumers; after withdrawal from the ground, water typically is treated, disinfected, or blended with other waters to maintain acceptable water quality. Regulatory thresholds apply to treated water that is served to the consumer, not to raw ground water. However, to provide some context for the results, concentrations of constituents measured in the raw ground water were compared with health-based thresholds established by the U.S. Environmental Protection Agency (USEPA) and California Department of Public Health (CDPH) and thresholds established for aesthetic concerns (secondary maximum contaminant levels, SMCL-CA) by CDPH. VOCs were detected in more than 90 percent (33 of 35) of grid wells. For all wells sampled for SFSG, nearly all VOC detections were below health-based thresholds, and most were less than one-tenth of the threshold values. Samples from seven wells had at least one detection of PCE, TCE, tetrachloromethane, NDMA, or 1,2,3-TCP at or above a health-based threshold. Pesticides were detected in about 90 percent (31 of 35) grid wells and all detections in samples from SFSG wells were below health-based thresholds. Major ions, trace elements, and nutrients in samples from 17 SFSG wells were all below health-based thresholds, with the exception of one detection of nitrate that was above the USEPA maximum contaminant level (MCL-US). With the exception of 14 samples having radon-222 above the proposed MCL-US, radioactive constituents were below health-based thresholds for 16 of the SFSG wells sampled. Total dissolved solids in 6 of the 24 SFSG wells that were sampled ha

California↗
USGS1994

Assessment of surface-water quality and water-quality control alternatives, Johnson Creek Basin, Oregon

Johnson Creek flows through a basin of approximately 51 square miles with mixed land uses over a reach of approximately 24 river miles from southeast of Gresham, Oregon, to its confluence with the Willamette River in Milwaukie, Oregon. Land uses within the basin include forested and agricultural lands, suburban residential, urban, and light industrial. Surface runoff and ground-water flow from the basin's areas of various land-use contain concentrations of some nutrients, trace elements, and organic compounds at levels exceeding U.S. Environmental Protection Agency (USEPA) criteria. Concentrations of dissolved cadmium, copper, lead, mercury, and silver, total recoverable chlordane, dieldrin, and dichlorodiphenyltrichloroethane (DDT) plus metabolites indicate that sources of at least one or more of these constituents exist in virtually every reach of Johnson Creek. Crystal Springs Creek is a major source of nutrients in lower Johnson Creek. Concentrations of dissolved nitrate and orthophosphorus in Johnson Creek are elevated at low flow, and are reduced by dilution when urban runoff flows into the creek during storms. Total-phosphorus concentrations exceed USEPA criteria at several sites in Johnson Creek during low flow, and at all sites during periods of storm runoff. The low-flow concentration of dissolved silver exceeded the USEPA Fresh Water Chronic Toxicity (FWCT) criterion only in Crystal Springs Creek. Concentrations of dissolved cadmium, copper, lead, and mercury exceeded FWCT criteria at selected sites in Johnson creek basin during storm runoff.

Water-Resources Investigations Report↗
USGS1995

Selected trace-element and organic contaminants in streambed sediments of the Potomac River Basin, August 1992

This report describes the occurrence and distribution of five selected contaminants in streambed sediments at 22 stream sites in the Potomac River Basin. Lead, mercury, and total DDT (dichlorodiphenyltrichloroethane) were detected at all sites, and chlordane and total PCB's (polychlorinated biphenyls) were detected at most sites. At six sites, streambed-sediment concentrations of contaminants were detected at levels with the potential to cause frequent adverse effects on aquatic organisms that live in the sediments. Chlordane was detected at these high levels at sampling sites on the Anacostia River, the North Branch Potomac River, Bull Run, and Accotink Creek; mercury was detected at these levels at sites on the South River and the South Fork Shenandoah River; and total PCB's were detected at these levels at the site on the South Fork Shenandoah River. The highest concentrations of all five contaminants generally occurred at sampling sites downstream from areas with industrial plants, urban centers, or orchard and agricultural activity. The occurrence of these contaminants in streambed sediments of the Potomac River Basin is of concern because the contaminants (1) are environmentally persistent, (2) are available for downstream transport during high streamflow periods, and (3) have the potential to cause adverse effects on the health of aquatic organisms and humans through bioaccumulation.

Potomac River Basin↗
USGS1995

Water quality of the Boca Raton canal system and effects of the Hillsboro Canal inflow, southeastern Florida, 1990-91

The City of Boca Raton in southeastern Palm Beach County, Florida, is an urban residential area that has sustained a constant population growth with subsequent increase in water use. The Boca Raton network of canals is controlled to provide for drainage of excess water, to maintain proper coastal ground-water levels to prevent saltwater intrusion, and to recharge the surficial aquifer system from which the city withdraws potable water. Most of the water supplied to the Boca Raton canal system and the surficial aquifer system, other than rainfall and runoff, is pumped from the Hillsboro Canal. The Biscayne aquifer, principal hydrogeologic unit of the surficial aquifer system, is highly permeable and there is a close relation between water levels in the canals and the aquifer. The amount of water supplied by seepage from the conservation areas is unknown. Because the Hillsboro Canal flows from Lake Okeechobee and Water Conservation Areas 1 and 2, which are places of more highly mineralized ground water and surface water, the canal is a possible source of contamination. Water samples were collected at 10 canal sites during wet and dry seasons and analyzed for major inorganic ions and related characteristics, nutrients, and trace elements. All concentrations were generally within or less than the drinking-water standards established by the Florida Department of Environmental Protection. The high concentrations of sodium and chloride that were detected in samples from the Boca Raton canal system are probably from the more mineralized water of the Hillsboro Canal. Other water-quality data, gathered from various sources from 1982 through 1991, did not indicate any significant changes nor trends. The data include pesticide and metal analyses of water samples and bottom sediments collected at four canal sites in the Boca Raton study area by the U.S. Geological Survey during 1982-84. The effects of the Hillsboro Canal on the water quality of the Boca Raton canal system are indicated by increased concentrations of sodium, chloride, dissolved solids, and total organic carbon. Concentrations of the constituents in the canal water generally decrease with distance from the Hillsboro Canal pumping station and are the result of dilution by receiving canal waters.

Florida↗
USGS1989

Use of stable carbon and nitrogen isotopes to trace the larval striped bass food chain in the Sacramento-San Joaquin Estuary, California, April to September 1985

To assess one potential cause for the decline of the striped bass fishery in the Sacramento-San Joaquin Estuary, stable carbon and nitrogen isotope ratios were used to examine the trophic structures of the larval striped bass food chain, and to trace the flux of these elements through the food chain components. Study results generally confirm a food chain consisting of the elements, phytoplankton/detritus-->zooplankton/Neomysis shrimp-->larval striped bass. The stable isotope ratios generally become more positive as one progresses from the lower to the higher trophic level food chain components, and no unusual trophic structure was found in the food chain. However, the data indicate an unidentified consumer organism occupying an intermediate position between the lower and higher trophic levels of the larval striped bass food chain. Based on expected trophic interactions, this unidentified consumer would have a stable carbon isotope ratio of about 28/mil and a stable nitrogen isotope ratio of about 8/mi. Three possible feeding stages for larval striped bass also were identified, based on their lengths. The smallest length fish seem to subsist on their yolk sac remnants, and the largest length fish subsist on Neomysis shrimp and zooplankton. The intermediate-length fish represent a transition stage between primary food sources and/or use of a mixture of food sources. (USGS)

Water-Resources Investigations Report↗
USGS2008

Ground-water quality data in the Central Eastside San Joaquin Basin 2006: Results from the California GAMA program

Ground-water quality in the approximately 1,695-square-mile Central Eastside study unit (CESJO) was investigated from March through June 2006 as part of the Statewide Basin Assessment Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Statewide Basin Assessment project was developed in response to the Groundwater Quality Monitoring Act of 2001 and is being conducted by the California State Water Resources Control Board (SWRCB) in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory (LLNL). The study was designed to provide a spatially unbiased assessment of raw ground-water quality within CESJO, as well as a statistically consistent basis for comparing water quality throughout California. Samples were collected from 78 wells in Merced and Stanislaus Counties. Fifty-eight of the 78 wells were selected using a randomized grid-based method to provide statistical representation of the study unit (grid wells). Twenty of the wells were selected to evaluate changes in water chemistry along selected lateral or vertical ground-water flow paths in the aquifer (flow-path wells). The ground-water samples were analyzed for a large number of synthetic organic constituents [volatile organic compounds (VOCs), gasoline oxygenates and their degradates, pesticides and pesticide degradates], constituents of special interest [perchlorate, N-nitrosodimethylamine (NDMA), and 1,2,3-trichloropropane (1,2,3-TCP)], inorganic constituents that can occur naturally [nutrients, major and minor ions, and trace elements], radioactive constituents, and microbial indicators. Naturally occurring isotopes [tritium, carbon-14, and uranium isotopes and stable isotopes of hydrogen, oxygen, nitrogen, sulfur, and carbon], and dissolved noble and other gases also were measured to help identify the source and age of the sampled ground water. Quality-control samples (blanks, replicates, samples for matrix spikes) were collected for approximately one-sixth of the wells, and the results for these samples were used to evaluate the quality of the data for the ground-water samples. Assessment of the quality-control results showed that the environmental data were of good quality, with low bias and low variability, and resulted in censoring of less than 0.3 percent of the detections found in ground-water samples. This study did not attempt to evaluate the quality of water delivered to consumers; after withdrawal from the ground, water typically is treated, disinfected, and (or) blended with other waters to maintain acceptable water quality. Regulatory thresholds apply to treated water that is served to the consumer, not to raw ground water. However, to provide some context for the results, concentrations of constituents measured in the raw ground water were compared with health-based thresholds established by the U.S. Environmental Protection Agency (USEPA) and California Department of Public Health (CADPH) and thresholds established for aesthetic concerns (secondary maximum contaminant levels, SMCL-CA) by CADPH. VOCs and pesticides were detected in approximately half of the grid wells, and all detections in samples from CESJO wells were below health-based thresholds. All detections of nutrients and major elements in grid wells also were below health-based thresholds. Most detections of constituents of special interest, trace elements, and radioactive constituents in samples from grid wells were below health-based thresholds. Exceptions included two detections of arsenic that were above the USEPA maximum contaminant level (MCL-US), one detection of lead above the USEPA action level (AL-US), and one detection of vanadium and three detections of 1,2,3-TCP that were above the CADPH notification levels (NL-CA). All detections of radioactive constituents were below health-based thresholds, although fourteen samples had activities of radon-222 above the lower proposed MCL-US. Most of the samples from CESJO grid wells had concentrations of major elements, total dissolved solids, and trace elements below the non-enforceable thresholds set for aesthetic concerns. A few samples contained manganese or total dissolved solids at concentrations above the SMCL-CA thresholds.

California↗
USGS2008

Ground-water quality data in the Kern County Subbasin study unit, 2006— Results from the California GAMA Program

Ground-water quality in the approximately 3,000 square-mile Kern County Subbasin study unit (KERN) was investigated from January to March, 2006, as part of the Priority Basin Assessment Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basin Assessment project was developed in response to the Groundwater Quality Monitoring Act of 2001, and is being conducted by the California State Water Resources Control Board (SWRCB) in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory (LLNL). The Kern County Subbasin study was designed to provide a spatially unbiased assessment of raw (untreated) ground-water quality within KERN, as well as a statistically consistent basis for comparing water quality throughout California. Samples were collected from 50 wells within the San Joaquin Valley portion of Kern County. Forty-seven of the wells were selected using a randomized grid-based method to provide a statistical representation of the ground-water resources within the study unit. Three additional wells were sampled to aid in the evaluation of changes in water chemistry along regional ground-water flow paths. The ground-water samples were analyzed for a large number of man-made organic constituents (volatile organic compounds [VOCs], pesticides, and pesticide degradates), constituents of special interest (perchlorate, N-nitrosodimethylamine [NDMA], and 1,2,3-trichloropropane [1,2,3-TCP]), naturally occurring inorganic constituents (nutrients, major and minor ions, and trace elements), radioactive constituents, and microbial indicators. Naturally occurring isotopes (tritium, carbon-14, and stable isotopes of hydrogen, oxygen, nitrogen, and carbon) and dissolved noble gases also were measured to help identify the source and age of the sampled ground water. Quality-control samples (blanks, replicates, and laboratory matrix spikes) were collected and analyzed at approximately 10 percent of the wells, and the results for these samples were used to evaluate the quality of the data from the ground-water samples. Assessment of the quality-control information resulted in censoring of less than 0.4 percent of the data collected for ground-water samples. This study did not attempt to evaluate the quality of water delivered to consumers; after withdrawal from the ground, raw ground water typically is treated, disinfected, or blended with other waters to maintain acceptable water quality. Regulatory thresholds apply, not to the raw ground water, but to treated water that is served to the consumer. However, to provide some context for the results, concentrations of constituents measured in the raw ground water were compared with health-based thresholds established by the U.S. Environmental Protection Agency (USEPA) and the California Department of Public Health (CDPH), and as well as with thresholds established for aesthetic concerns (secondary maximum contaminant levels, SMCL-CA) by CDPH. VOCs and pesticides each were detected in approximately 60 percent of the grid wells, and detections of all compounds but one were below health-based thresholds. The fumigant, 1,2-dibromo-3-chloropropane (DBCP), was detected above the USEPA maximum contaminant level (MCL-US) in one sample. Detections of most inorganic constituents were also below health-based thresholds. Constituents detected above health-based thresholds include: nitrate, (MCL-US, 2 samples), arsenic (MCL-US, 2 samples), and vanadium (California notification level, NL-CA, 1 sample). All detections of radioactive constituents were below health-based thresholds, although nine samples had activities of radon-222 above the lower proposed MCL-US. Most of the samples from KERN wells had concentrations of major elements, total dissolved solids, and trace elements below the non-enforceable thresholds set for aesthetic concerns.

California↗
USGS2005

Statistical characterization of a large geochemical database and effect of sample size

The authors investigated statistical distributions for concentrations of chemical elements from the National Geochemical Survey (NGS) database of the U.S. Geological Survey. At the time of this study, the NGS data set encompasses 48,544 stream sediment and soil samples from the conterminous United States analyzed by ICP-AES following a 4-acid near-total digestion. This report includes 27 elements: Al, Ca, Fe, K, Mg, Na, P, Ti, Ba, Ce, Co, Cr, Cu, Ga, La, Li, Mn, Nb, Nd, Ni, Pb, Sc, Sr, Th, V, Y and Zn. The goal and challenge for the statistical overview was to delineate chemical distributions in a complex, heterogeneous data set spanning a large geographic range (the conterminous United States), and many different geological provinces and rock types. After declustering to create a uniform spatial sample distribution with 16,511 samples, histograms and quantile-quantile (Q-Q) plots were employed to delineate subpopulations that have coherent chemical and mineral affinities. Probability groupings are discerned by changes in slope (kinks) on the plots. Major rock-forming elements, e.g., Al, Ca, K and Na, tend to display linear segments on normal Q-Q plots. These segments can commonly be linked to petrologic or mineralogical associations. For example, linear segments on K and Na plots reflect dilution of clay minerals by quartz sand (low in K and Na). Minor and trace element relationships are best displayed on lognormal Q-Q plots. These sensitively reflect discrete relationships in subpopulations within the wide range of the data. For example, small but distinctly log-linear subpopulations for Pb, Cu, Zn and Ag are interpreted to represent ore-grade enrichment of naturally occurring minerals such as sulfides. None of the 27 chemical elements could pass the test for either normal or lognormal distribution on the declustered data set. Part of the reasons relate to the presence of mixtures of subpopulations and outliers. Random samples of the data set with successively smaller numbers of data points showed that few elements passed standard statistical tests for normality or log-normality until sample size decreased to a few hundred data points. Large sample size enhances the power of statistical tests, and leads to rejection of most statistical hypotheses for real data sets. For large sample sizes (e.g., n > 1000), graphical methods such as histogram, stem-and-leaf, and probability plots are recommended for rough judgement of probability distribution if needed. ?? 2005 Elsevier Ltd. All rights reserved.

Applied Geochemistry↗
USGS1994

Geologic framework and hydrogeologic characteristics of the Edwards Aquifer outcrop, Comal County, Texas

All of the hydrogeologic subdivisions within the Edwards aquifer outcrop in Comal County have some porosity and permeability. The most porous and permeable appear to be hydrogeologic subdivision VI, the Kirschberg evaporite member of the Kainer Formation; hydrogeologic subdivision III, the leached and collapsed members, undivided; and hydrogeologic subdivision II, the cyclic and marine members, undivided, of the Person Formation. The two types of porosity in the Edwards aquifer outcrop are fabric selective, which is related to depositional or diagenetic elements and typically exists in specific stratigraphic horizons; and not fabric selective, which can exist in any litho strati graphic horizon. Permeability, the capacity of porous rock to transmit water, depends on the physical properties of the rock such as pore size, shape, distribution, fissuring, and dissolution. Two faults, Comal Springs and Hueco Springs, completely, or almost completely, offset the Edwards aquifer along much of their respective traces across Comal County. Porous and permeable Edwards aquifer limestone is juxtaposed against impermeable upper confining units in these areas. These faults completely, or almost completely, offset the Edwards aquifer and are thought to be barriers or partial barriers to groundwater flow where the beds are juxtaposed. In Comal County, the Edwards aquifer is probably most vulnerable to surface contamination in the rapidly urbanizing areas on the Edwards aquifer outcrop. Possible contamination can result from spills, leakage of hazardous materials, or runoff onto the intensely faulted and fractured, karstic limestone outcrops characteristic of the recharge zone.

Texas↗
USGS2013

Status and understanding of groundwater quality in the South Coast Range-Coastal study unit, 2008: California GAMA Priority Basin Project

Groundwater quality in the South Coast Range–Coastal (SCRC) study unit was investigated from May through November 2008 as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in the Southern Coast Range hydrologic province and includes parts of Santa Barbara and San Luis Obispo Counties. The GAMA Priority Basin Project is conducted by the U.S. Geological Survey (USGS) in collaboration with the California State Water Resources Control Board and the Lawrence Livermore National Laboratory. The GAMA Priority Basin Project was designed to provide a statistically unbiased, spatially distributed assessment of untreated groundwater quality within the primary aquifer system. The primary aquifer system is defined as that part of the aquifer corresponding to the perforation interval of wells listed in the California Department of Public Health (CDPH) database for the SCRC study unit. The assessments for the SCRC study unit were based on water-quality and ancillary data collected in 2008 by the USGS from 55 wells on a spatially distributed grid, and water-quality data from the CDPH database. Two types of assessments were made: (1) status, assessment of the current quality of the groundwater resource, and (2) understanding, identification of the natural and human factors affecting groundwater quality. Water-quality and ancillary data were collected from an additional 15 wells for the understanding assessment. The assessments characterize untreated groundwater quality, not the quality of treated drinking water delivered to consumers by water purveyors. The first component of this study, the status assessment of groundwater quality, used data from samples analyzed for anthropogenic constituents such as volatile organic compounds (VOCs) and pesticides, as well as naturally occurring inorganic constituents such as major ions and trace elements. Although the status assessment applies to untreated groundwater, Federal and California regulatory and non-regulatory water-quality benchmarks that apply to drinking water are used to provide context for the results. Relative-concentrations (sample concentration divided by benchmark concentration) were used for evaluating groundwater. A relative-concentration greater than (>) 1.0 indicates a concentration greater than the benchmark and is classified as high. Inorganic constituents are classified as moderate if relative-concentrations are >0.5 and less than or equal to (≤) 1.0, or low if relative-concentrations are ≤0.5. For organic constituents, the boundary between moderate and low relative-concentrations was set at 0.1. Aquifer-scale proportion was used in the status assessment as the primary metric for evaluating regional-scale groundwater quality. High aquifer-scale proportion is defined as the areal percentage of the primary aquifer system with a high relative-concentration for a particular constituent or class of constituents. Moderate and low aquifer-scale proportions were defined as the areal percentage of the primary aquifer system with moderate and low relative-concentrations, respectively. Two statistical approaches—grid-based and spatially weighted—were used to evaluate aquifer-scale proportions for individual constituents and classes of constituents. Grid-based and spatially weighted estimates were comparable for the study (within 90 percent confidence intervals). For inorganic constituents with human-health benchmarks, relative-concentrations were high for at least one constituent for 33 percent of the primary aquifer system in the SCRC study unit. Arsenic, molybdenum, and nitrate were the primary inorganic constituents with human-health benchmarks that were detected at high relative-concentrations. Inorganic constituents with aesthetic benchmarks, referred to as secondary maximum contaminant levels (SMCLs), had high relative-concentrations for 35 percent of the primary aquifer system. Iron, manganese, total dissolved solids (TDS), and sulfate were the inorganic constituents with SMCLs detected at high relative-concentrations. In contrast to inorganic constituents, organic constituents with human-health benchmarks were not detected at high relative-concentrations in the primary aquifer system in the SCRC study unit. Of the 205 organic constituents analyzed, 21 were detected—13 with human-health benchmarks. Perchloroethene (PCE) was the only VOC detected at moderate relative-concentrations. PCE, dichlorodifluoromethane (CFC-12), and chloroform were detected in more than 10 percent of the primary aquifer system. Of the two special-interest constituents, one was detected; perchlorate, which has a human-health benchmark, was detected at moderate relative-concentrations in 29 percent of the primary aquifer system and had a detection frequency of 60 percent in the SCRC study unit. The second component of this study, the understanding assessment, identified the natural and human factors that may have affected groundwater quality in the SCRC study unit by evaluating statistical correlations between water-quality constituents and potential explanatory factors. The potential explanatory factors evaluated were land use, septic tank density, well depth and depth to top-of-perforations, groundwater age, density and distance to the nearest formerly leaking underground fuel tank (LUFT), pH, and dissolved oxygen (DO) concentration. Results of the statistical evaluations were used to explain the occurrence and distribution of constituents in the study unit. DO was the primary explanatory factor influencing the concentrations of many inorganic constituents. Arsenic, iron, and manganese concentrations increased as DO concentrations decreased, consistent with patterns expected as a result of reductive dissolution of iron and (or) manganese oxides in aquifer sediments. Molybdenum concentrations increased in anoxic conditions and in oxic conditions with high pH, reflecting two mechanisms for the mobilization of molybdenum—reductive dissolution and pH-dependent desorption under oxic conditions from aquifer sediments. Nitrate concentrations decreased as DO concentrations decreased which would be consistent with degradation of nitrate under anoxic conditions (denitrification). It also is possible that nitrate concentrations decreased in relation to increasing depth and groundwater age and not as a result of denitrification. Groundwater age was another explanatory factor frequently correlated to several inorganic constituents. Iron and manganese concentrations were higher in pre-modern (water recharged before 1952) or mixed-age groundwater. This correlation is one indication that iron and manganese are from natural sources. Nitrate, TDS, and sulfate concentrations were higher in modern groundwater (water recharged since 1952) and may indicate that human activities increase concentrations of nitrate, TDS, and sulfate. Land use was a third explanatory factor frequently correlated with inorganic constituents. Nitrate, TDS, and sulfate concentrations were higher in agricultural land-use areas than in natural land-use areas, indicating that increased concentrations may be a result of agricultural practices. Organic constituents usually were detected at low relative-concentrations; therefore, statistical analyses of relations to explanatory factors usually were done for classes of constituents (for example, pesticides or solvents) as well as for selected constituents. The number of VOCs detected in a well was not correlated to any of the explanatory factors evaluated. The number of pesticide and solvent detections and PCE and CFC-12 concentrations were higher in modern groundwater than in pre-modern groundwater. PCE and CFC-12 also were positively correlated to the density of LUFTs. PCE was negatively correlated to natural land use. Chloroform concentrations were positively correlated to the density of septic systems. Perchlorate concentrations were greater in agricultural areas than in urban or natural areas. Correlation of perchlorate with DO may indicate that perchlorate biodegradation under anoxic conditions may occur. Anthropogenic sources have contributed perchlorate to groundwater in the SCRC study unit, although low levels of perchlorate may occur naturally.

California↗
USGS2011

Status and understanding of groundwater quality in the San Diego Drainages Hydrogeologic Province, 2004: California GAMA Priority Basin Project

Groundwater quality in the approximately 3,900-square-mile (mi 2 ) San Diego Drainages Hydrogeologic Province (hereinafter San Diego) study unit was investigated from May through July 2004 as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in southwestern California in the counties of San Diego, Riverside, and Orange. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory. The GAMA San Diego study was designed to provide a statistically robust assessment of untreated-groundwater quality within the primary aquifer systems. The assessment is based on water-quality and ancillary data collected by the USGS from 58 wells in 2004 and water-quality data from the California Department of Public Health (CDPH) database. The primary aquifer systems (hereinafter referred to as the primary aquifers) were defined by the depth interval of the wells listed in the California Department of Public Health (CDPH) database for the San Diego study unit. The San Diego study unit consisted of four study areas: Temecula Valley (140 mi 2 ), Warner Valley (34 mi 2 ), Alluvial Basins (166 mi 2 ), and Hard Rock (850 mi 2 ). The quality of groundwater in shallow or deep water-bearing zones may differ from that in the primary aquifers. For example, shallow groundwater may be more vulnerable to surficial contamination than groundwater in deep water-bearing zones. This study had two components: the status assessment and the understanding assessment. The first component of this study-the status assessment of the current quality of the groundwater resource-was assessed by using data from samples analyzed for volatile organic compounds (VOC), pesticides, and naturally occurring inorganic constituents, such as major ions and trace elements. The status assessment is intended to characterize the quality of groundwater resources within the primary aquifers of the San Diego study unit, not the treated drinking water delivered to consumers by water purveyors. The second component of this study-the understanding assessment-identified the natural and human factors that affect groundwater quality by evaluating land use, well construction, and geochemical conditions of the aquifer. Results from these evaluations were used to help explain the occurrence and distribution of selected constituents in the study unit. Relative-concentrations (sample concentration divided by benchmark concentration) were used as the primary metric for relating concentrations of constituents in groundwater samples to water-quality benchmarks for those constituents that have Federal and (or) California benchmarks. For organic and special-interest constituents, relative-concentrations were classified as high (> 1.0), moderate (> 0.1 and &le;1.0), and low (&le;0.1). For inorganic constituents, relative concentrations were classified as high (> 1.0), moderate (> 0.5 and &le;1.0), and low (&le;0.5). Grid-based and spatially weighted approaches were then used to evaluate the proportion of the primary aquifers (aquifer-scale proportions) with high, moderate, and low relative-concentrations for individual compounds and classes of constituents. One or more of the inorganic constituents with health-based benchmarks were high (relative to those benchmarks) in 17.6 percent of the primary aquifers in the Temecula Valley, Warner Valley, and Alluvial Basins study areas (hereinafter also collectively referred to as the Alluvial Fill study areas because they are composed of alluvial fill aquifers), and in 25.0 percent of the Hard Rock study area. Inorganic constituents with health-based benchmarks that were frequently detected at high relative-concentrations included vanadium (V), arsenic (As), and boron (B). Vanadium and As concentrations were not significantly correlated to either urban or agricultural land use indicating natural sources as the primary contributors of these constituents to groundwater. The positive correlation of B concentration to urban land-use was significant which indicates that anthropogenic activities are a contributing source of B to groundwater. The correlation of V, As and B concentrations to pH was positive, indicating that in alkaline groundwater these constituents are being desorbed from, or being inhibited from adsorbing to, particle surfaces. Inorganic constituents with aesthetic benchmarks that were detected at high relative-concentrations include manganese (Mn), iron (Fe), and total dissolved solids (TDS). In the Alluvial Fill study areas, Mn and TDS were detected at high relative-concentrations in 13.7 percent of the primary aquifers, and Fe in 6.9 percent. In the Hard Rock study area, Mn was detected at high relative-concentrations in 33.3 percent of the primary aquifers, and TDS in 16.7 percent; Fe was not detected at high relative-concentrations. Total dissolved solids concentrations were significantly correlated to agricultural land use suggesting that agricultural practices are a contributing source of TDS to groundwater. Manganese and Fe concentrations were highest in groundwater with low dissolved oxygen and pH indicating that the reductive dissolution of oxyhydroxides may be an important mechanism for the mobilization of Mn and Fe in groundwater. TDS concentrations were highest in shallow wells and in modern (< 50 yrs) groundwater which indicates anthropogenic activities as a source of TDS concentrations in groundwater. The relative-concentrations of organic constituents with health-based benchmarks were high in 3.0 percent of the primary aquifers in the Alluvial Fill study areas. A single detection in the Alluvial Basins study area of the discontinued gasoline oxygenate methyl tert-butyl ether (MTBE) was the only organic constituent detected at a high relative-concentration; high relative-concentrations of these constituents were not detected in the Hard Rock study area. Twelve of 88 VOCs and 14 of 123 pesticides and pesticide degradates analyzed in grid wells were detected. Chloroform was the only VOC detected in more than 10 percent of the grid wells. The herbicides simazine, atrazine, and prometon were each detected in greater than 10 percent of the grid wells. Perchlorate was detected in 22 percent of the grid wells sampled. The understanding assessment showed a significant correlation of trihalomethanes (THMs) and solvents to urban land-use, indicating that detections of these constituents are more likely to occur in groundwater underlying urbanized areas of the study unit. MTBE concentrations were negatively correlated to the distance from the nearest leaking underground fuel tank, indicating that point sources are the most significant contributing factor for MTBE concentrations to groundwater in the study unit. The positive correlation of THM and herbicide concentrations to modern groundwater was significant, as was the negative correlation of herbicide concentrations to pH and anoxic groundwater. The negative correlation of herbicides to pH and anoxic groundwater was likely due to the fact that these constituents were detected more frequently in shallow wells where groundwater conditions tend to be oxic with relatively low pH.

California↗
USGS2003

Surface-water/ground-water interaction of the Spokane River and the Spokane Valley/Rathdrum Prairie aquifer, Idaho and Washington

Historical mining in the Coeur d’Alene River Basin of northern Idaho has resulted in elevated concentrations of some trace metals (particularly cadmium, lead, and zinc) in water and sediment of Coeur d’Alene Lake and downstream in the Spokane River in Idaho and Washington. These elevated trace-metal concentrations in the Spokane River have raised concerns about potential contamination of ground water in the underlying Spokane Valley/Rathdrum Prairie aquifer, the primary source of drinking water for the city of Spokane and surrounding areas. A study conducted as part of the U.S. Geological Survey’s National Water-Quality Assessment Program examined the interaction of the river and aquifer using hydrologic and chemical data along a losing reach of the Spokane River. The river and ground water were extensively monitored over a range of hydrologic conditions at a streamflow-gaging station and 25 monitoring wells situated from 40 to 3,500 feet from the river. River stage, ground-water levels, water temperature, and specific conductance were measured hourly to biweekly. Water samples were collected on nearly a monthly basis between 1999 and 2001 from the Spokane River and were collected up to nine times between June 2000 and August 2001 from the monitoring wells. Hydrologic and chemical data indicate that the Spokane River recharges the Spokane Valley/ Rathdrum Prairie aquifer along a 17-mile reach between Post Falls, Idaho, and Spokane, Washington. Ground-water levels in the near-river aquifer (less than 300 feet from the river) indicate variably saturated conditions below the river and a ground-water flow gradient away from the losing reach of the river. Calculated monthly mean losses, during water years 2000 and 2001 along a nearly 7-mile reach between two gages, ranged from near 69 to 810 cubic feet per second. Losses generally increased with increased streamflow. However, late summer warm water temperatures also appear to be a factor as losses increased due to lower viscosity as water temperatures increased. Chemical data indicated that river recharge may influence ground-water chemistry as far as 3,000 feet from the river, but ground water within a few hundred feet of the river is most affected. Major-ion concentrations, stable isotopes, and temperature of the river and ground water from near-river wells were similar and exhibited similar temporal trends, whereas ground water from wells located farther from the river generally had higher major-ion concentrations and more stable temperatures and chemistry. Although trace-element concentrations sometimes exceeded aquatic-life criteria in the water of the Spokane River and were elevated above national median values in the bed sediment, trace-element concentrations of all river and ground-water samples were at levels less than U.S. Environmental Protection Agency drinking-water standards. The Spokane River appears to be a source of cadmium, copper, zinc, and possibly lead in the near-river ground water. Dissolved cadmium, copper, and lead concentrations generally were less than 1 microgram per liter (µg/L) in the river water and ground water. During water year 2001, dissolved zinc concentrations were similar in water from near-river wells (17-71 µg/L) and the river water (22-66 µg/L), but were less than detection levels in wells farther from the river. Arsenic, found to be elevated in ground water in parts of the aquifer, does not appear to have a river source. Although the river does influence the ground-water chemistry in proximity to the river, it does not appear to adversely affect the ground-water quality to a level of human-health concern.

Idaho;Washington↗
USGS2012

Distribution and variation of arsenic in Wisconsin surface soils, with data on other trace elements

A total of 664 soil samples distributed among different geographic regions and soil types were collected across Wisconsin to describe the distribution of arsenic relative to parent material, soil texture, and drainage class. Soils from 6 inches in depth were composited, digested in aqua regia, and analyzed for 17 trace elements. Observed soil arsenic concentrations range from a high of 39 milligrams per kilogram (mg/kg) to less than the laboratory detection limit of 1 mg/kg. Ten samples with soil arsenic concentrations greater than 8.5 mg/kg were determined to be significantly separate from the main cluster of the dataset. With these outliers removed, overall soil arsenic concentrations in Wisconsin have a median value of 1.8 mg/kg, and the 95-percent upper confidence limit of the mean is 2.4 mg/kg. Soils with sandy glacial outwash as a parent material have a lower median arsenic concentration (1.0 mg/kg) than soils forming in other parent materials (1.5 to 3.0 mg/kg). Soil texture and drainage category also influence median arsenic concentration. Finer grained soils have a higher observed range of concentrations. For loamy and loess-dominated soil groups, drainage category influences the median arsenic concentration and observed range of values, but a consistent relationship within the data is not apparent. Statistical analysis of the 16 other elements are presented in this report, but the relationships of concentrations to soil properties or geographic areas were not examined.

Wisconsin↗
USGS2009

Ground-Water Quality Data in the Coachella Valley Study Unit, 2007: Results from the California GAMA Program

Ground-water quality in the approximately 820 square-mile Coachella Valley Study Unit (COA) was investigated during February and March 2007 as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basin Project was developed in response to the Groundwater Quality Monitoring Act of 2001, and is being conducted by the U.S. Geological Survey (USGS) in cooperation with the California State Water Resources Control Board (SWRCB). The study was designed to provide a spatially unbiased assessment of raw ground water used for public-water supplies within the Coachella Valley, and to facilitate statistically consistent comparisons of ground-water quality throughout California. Samples were collected from 35 wells in Riverside County. Nineteen of the wells were selected using a spatially distributed, randomized grid-based method to provide statistical representation of the study unit (grid wells). Sixteen additional wells were sampled to evaluate changes in water chemistry along selected ground-water flow paths, examine land use effects on ground-water quality, and to collect water-quality data in areas where little exists. These wells were referred to as 'understanding wells'. The ground-water samples were analyzed for a large number of organic constituents (volatile organic compounds [VOC], pesticides and pesticide degradates, pharmaceutical compounds, and potential wastewater-indicator compounds), constituents of special interest (perchlorate and 1,2,3-trichloropropane [1,2,3-TCP]), naturally occurring inorganic constituents (nutrients, major and minor ions, and trace elements), radioactive constituents, and microbial indicators. Naturally occurring isotopes (uranium, tritium, carbon-14, and stable isotopes of hydrogen, oxygen, and boron), and dissolved noble gases (the last in collaboration with Lawrence Livermore National Laboratory) also were measured to help identify the source and age of the sampled ground water. A quality-control sample (blank, replicate, or matrix spike) was collected at approximately one quarter of the wells, and the results for these samples were used to evaluate the quality of the data for the ground-water samples. Assessment of the quality-control information resulted in V-coding less than 0.1 percent of the data collected. This study did not attempt to evaluate the quality of water delivered to consumers; after withdrawal from the ground, water typically is treated, disinfected, and (or) blended with other waters to maintain acceptable water quality. Regulatory thresholds apply to treated water that is supplied to the consumer, not to raw ground water. However, to provide some context for the results, concentrations of constituents measured in the raw ground water were compared with health-based thresholds established by the U.S. Environmental Protection Agency (USEPA) and the California Department of Public Health (CDPH) and thresholds established for aesthetic purposes (secondary maximum contaminant levels, SMCL-CA) by CDPH. Most constituents detected in ground-water samples were at concentrations below drinking-water thresholds. Volatile organic compounds, pesticides, and pesticide degradates were detected in less than one-third of the grid well samples collected. All VOC and pesticide concentrations measured were below health-based thresholds. Potential waste-water indicators were detected in less than half of the wells sampled, and no detections were above health-based thresholds. Perchlorate was detected in seven grid wells; concentrations from two wells were above the CDPH maximum contaminant level (MCL-CA). Most detections of trace elements in samples collected from COA Study Unit wells were below water-quality thresholds. Exceptions include five samples of arsenic that were above the USEPA maximum contaminant level (MCL-US), two detections of boron above the CDPH notification level (NL-CA), and two detections of mol

Data Series↗