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USGS2009

Factors affecting water quality in selected carbonate aquifers in the United States, 1993-2005

Carbonate aquifers are an important source of water in the United States; however, these aquifers can be particularly susceptible to contamination from the land surface. The U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program collected samples from wells and springs in 12 carbonate aquifers across the country during 1993–2005; water-quality results for 1,042 samples were available to assess the factors affecting ground-water quality. These aquifers represent a wide range of climate, land-use types, degrees of confinement, and other characteristics that were compared and evaluated to assess the effect of those factors on water quality. Differences and similarities among the aquifers were also identified. Samples were analyzed for major ions, radon, nutrients, 47 pesticides, and 54 volatile organic compounds (VOCs). Geochemical analysis helped to identify dominant processes that may contribute to the differences in aquifer susceptibility to anthropogenic contamination. Differences in concentrations of dissolved oxygen and dissolved organic carbon and in ground-water age were directly related to the occurrence of anthropogenic contaminants. Other geochemical indicators, such as mineral saturation indexes and calcium-magnesium molar ratio, were used to infer residence time, an indirect indicator of potential for anthropogenic contamination. Radon exceeded the U.S. Environmental Protection Agency proposed Maximum Contaminant Level (MCL) of 300 picocuries per liter in 423 of 735 wells sampled, of which 309 were drinking-water wells. In general, land use, oxidation-reduction (redox) status, and degree of aquifer confinement were the most important factors affecting the occurrence of anthropogenic contaminants. Although none of these factors individually accounts for all the variation in water quality among the aquifers, a combination of these characteristics accounts for the majority of the variation. Unconfined carbonate aquifers that had high percentages of urban or agricultural land, or a combination of both, had higher concentrations and higher frequency of detections for most of the anthropogenic contaminants than areas with other combinations of land use and degree of aquifer confinement. Redox status is an indicator of more recently recharged water and affects the fate of some contaminants. Median concentrations of nitrate were highest in the Valley and Ridge and Piedmont aquifers and lowest in the Biscayne and Silurian-Devonian/Upper carbonate aquifers. Nitrate concentrations were significantly higher in unconfined aquifers than in confined aquifers and semiconfined/mixed confined aquifers (wells in aquifers with breached confining layers or wells open to both a confined and an unconfined aquifer). Water recharged after 1953 had significantly higher concentrations of nitrate than water recharged prior to 1953. Redox status was also a key factor affecting nitrate concentrations; in recently recharged waters, samples in oxic waters had significantly higher concentrations of nitrate than anoxic waters, regardless of land use in the area around the well. Samples from 54 wells (5 percent) exceeded the U.S. Environmental Protection Agency MCL of 10 mg/L for nitrate in drinking water. Most of the samples exceeding the drinking-water standard (52 samples, or 5 percent) were in domestic supply wells in agricultural areas. The Piedmont and Valley and Ridge aquifers had the largest number of samples (45) exceeding the MCL; in the remaining aquifers only 9 samples had concentrations of nitrate that exceeded the MCL (about 1 percent). None of the water recharged prior to 1953 and only a single sample from a confined aquifer had nitrate concentrations that exceeded 10 mg/L as N. Wells were sampled for a minimum of 47 pesticides. Detection frequencies and comparisons varied depending on the assessment level used. At least 1 of the 47 pesticides was detected at 510 (50 percent) of the 1,027 sites where pesticide data were available using the ‘all detections’ assessment level—that is, including any quantified detection as well as any estimated values where the compound was definitively detected. Multiple pesticides were frequently detected in a sample of water from a site; 34 percent of the samples had two to five pesticides detected in the same sample, and 4 percent of the samples had six or more pesticides detected. Dieldrin was detected at 20 sites, 9 of which were from either domestic or public supply wells, at a concentration above the Health-Based Screening Level (HBSL) of 0.002 µg/L. Diazinon was detected at a concentration greater than the HBSL of 1 µg/L at a single site, which was also a domestic supply well. These are the only samples where a pesticide exceeded a human-health benchmark. The most frequently occurring pesticide compounds were four herbicides—atrazine, simazine, metolachlor, and prometon—and deethylatrazine, a degradate of atrazine. These pesticides typically were detected at concentrations that were less than 10 percent of a human-health benchmark. Of the four frequently occurring pesticides, only samples for atrazine (3 percent) and simazine (0.1 percent) had concentrations that exceeded 10 percent of the human-health benchmark; most of these cases were in agricultural areas. It is important to note, however, that the most frequently occurring pesticide degradate compound—deethylatrazine—has no human-health benchmark. Using a common assessment level of 0.01 µg/L, four of the aquifers—Biscayne, Mississippian, Piedmont, and Valley and Ridge—had at least one of these five compounds detected in more than 30 percent of the wells sampled. These four aquifers, along with the Ordovician, Ozark Plateaus, and Prairie du Chien aquifers were the aquifers or aquifer systems that had concentrations of pesticides that exceeded 10 percent of a human-health benchmark. Water recharged after 1953 had a significantly higher percentage of detections of pesticides than water recharged before 1953, and water from unconfined aquifers had a significantly higher percentage of detections of pesticides than water from confined or semiconfined/mixed confined aquifers. Water from sites in unconfined aquifers, where land use was agricultural or urban, accounted for the vast majority of detections of pesticides. Dissolved oxygen concentration was positively related to pesticide occurrence, which likely reflects the positive association between dissolved oxygen concentration and recently recharged water. Water samples were collected for analysis of VOCs at 793 sites—154 samples were analyzed for 54 VOCs from 1993 through 1995 and 639 samples were analyzed for 86 VOCs from 1996 through 2005. Twenty percent of samples contained one or more VOCs at concentrations greater than or equal to 0.2 µg/L (159 of 793 samples). The aquifers with the highest percentage of samples containing one or more VOCs were the Castle Hayne (about 41 percent of samples) and Biscayne aquifers (34 percent). The most frequently detected VOCs were chloroform, tetrahydrofuran, tetrachloroethene (PCE), toluene, acetone, ethylmethylketone, methyl tert-butyl ether (MTBE), and trichloroethene (TCE). Low-level concentrations of VOCs occurred in a much larger percentage of a subset of the data (the 639 samples analyzed using a low-level analytical method). In these samples, 69 percent of the 639 samples contained 1 or more VOCs, indicating the vulnerability of the carbonate aquifers to low-level VOC contamination. Four VOCs were detected at concentrations exceeding their respective MCLs in five samples, all of which were from drinking-water wells. Vinyl chloride concentrations exceeded the MCL of 2 µg/L in two samples from urban areas in the unconfined Biscayne aquifer. PCE, TCE, and 1,2-dichloropropane each had one sample with a concentration greater than their MCLs of 5 µg/L; these samples were from agricultural and urban areas in the unconfined Mississippian aquifer. Water quality in the 12 carbonate aquifers was highly variable. Most of the samples met drinking-water standards. The occurrence of anthropogenic contaminants was related to contaminant sources but also was affected by degree of aquifer confinement, ground-water age, and redox status. Areas with higher amounts of agricultural or urban land in unconfined aquifers were the most likely to have elevated concentrations of anthropogenic contaminants.

Scientific Investigations Report↗

USGS2011

Onshore and offshore geologic map of the Coal Oil Point area, southern California

Geologic maps that span the shoreline and include both onshore and offshore areas are potentially valuable tools that can lead to a more in depth understanding of coastal environments. Such maps can contribute to the understanding of shoreline change, geologic hazards, both offshore and along-shore sediment and pollutant transport. They are also useful in assessing geologic and biologic resources. Several intermediate-scale (1:100,000) geologic maps that include both onshore and offshore areas (herein called onshore-offshore geologic maps) have been produced of areas along the California coast (see Saucedo and others, 2003; Kennedy and others, 2007; Kennedy and Tan, 2008), but few large-scale (1:24,000) maps have been produced that can address local coastal issues. A cooperative project between Federal and State agencies and universities has produced an onshore-offshore geologic map at 1:24,000 scale of the Coal Oil Point area and part of the Santa Barbara Channel, southern California (fig. 1). As part of the project, the U.S. Geological Survey (USGS) and the California Geological Survey (CGS) hosted a workshop (May 2nd and 3rd, 2007) for producers and users of coastal map products (see list of participants) to develop a consensus on the content and format of onshore-offshore geologic maps (and accompanying GIS files) so that they have relevance for coastal-zone management. The USGS and CGS are working to develop coastal maps that combine geospatial information from offshore and onshore and serve as an important tool for addressing a broad range of coastal-zone management issues. The workshop was divided into sessions for presentations and discussion of bathymetry and topography, geology, and habitat products and needs of end users. During the workshop, participants reviewed existing maps and discussed their merits and shortcomings. This report addresses a number of items discussed in the workshop and details the onshore and offshore geologic map of the Coal Oil Point area. Results from this report directly address issues raised in the California Ocean Protection Act (COPA) Five Year Strategic Plan. For example, one of the guiding principles of the COPA five-year strategic plan is to 'Recognize the interconnectedness of the land and the sea, supporting sustainable uses of the coast and ensuring the health of ecosystems.' Results from this USGS report directly connect the land and sea with the creation of both a seamless onshore and offshore digital terrain model (DTM) and geologic map. One of the priority goals (and objectives) of the COPA plan is to 'monitor and map the ocean environment to provide data about conditions and trends.' Maps within this report provide land and sea geologic information for mapping and monitoring nearshore sediment processes, pollution transport, and sea-level rise and fall.

California↗

USGS2002

VOCs, pesticides, nitrate, and their mixtures in groundwater used for drinking water in the United States

Samples of untreated groundwater from 1255 domestic drinking-water wells and 242 public supply wells were analyzed as part of the National Water-Quality Assessment Program of the U.S. Geological Survey between 1992 and 1999. Wells were sampled to define the regional quality of the groundwater resource and, thus, were distributed geographically across large aquifers, primarily in rural areas. For each sample, as many as 60 volatile organic compounds (VOCs), 83 pesticides, and nitrate were analyzed. On the basis of previous studies, nitrate concentrations as nitrogen ≥3 mg/L were considered to have an anthropogenic origin. VOCs were detected more frequently (44%) than pesticides (38%) or anthropogenic nitrate (28%). Seventy percent of the samples contained at least one VOC, pesticide, or anthropogenic nitrate; 47% contained at least two compounds; and 33% contained at least three compounds. The combined concentrations of VOCs and pesticides ranged from about 0.001 to 100 μg/L, with a median of 0.02 μg/L. Water from about 12% of the wells contained one or more compounds that exceeded U.S. Environmental Protection Agency drinking-water standards or human health criteria, primarily because of nitrate concentrations exceeding the maximum contaminant level in domestic wells. A mixture is defined as a unique combination of two or more particular compounds, regardless of the presence of other compounds that may occur in the same sample. There were 100 mixtures (significantly associated with agricultural land use) that had a detection frequency between 2% and 19%. There were 302 mixtures (significantly associated with urban land use) that had a detection frequency between 1% and <2%. Only 14 compounds (seven VOCs, six pesticides, and nitrate) contributed over 95% of the detections in these 402 mixtures; however, most samples with these mixtures also contain a variety of other compounds.

Environmental Science & Technology↗

USGS1988

Reconnaissance investigation of water quality, bottom sediment, and biota associated with irrigation drainage in the Kendrick Reclamation Project Area, Wyoming, 1986-87

A reconnaissance investigation of the Kendrick Reclamation Project in central Wyoming was conducted during 1986-87 to determine if irrigation drainage has caused or has the potential to cause harmful effects on human health, fish, and wildlife, or other water uses. The investigation of the Kendrick Reclamation Project is one of nine similar investigations being conducted in the western conterminous United States as part of the Department of the Interior 's Irrigation Drainage Program. Samples of surface water were collected at 10 sites and ground water at 5 sites. Surface-water analyses included trace elements, radiochemicals, and pesticides. Concentrations in the water generally were less than national standards for public water supplies, with the exception of selenium. The median concentration of dissolved selenium was 7.5 microgm/L in 24 samples of surface and groundwater. Of the 11 samples that contained dissolved- selenium concentrations greater than the national standard for public water supplies of 10 microgm/L, 10 of the samples were collected at sites on streams that are not used for public water supplies; the eleventh sample was collected from a shallow well. Dissolved-selenium concentrations ranged from less than 1 to 300 microgm/L. Concentrations of dissolved selenium in the North Platte River, which supplies drinking water for several municipalities, ranged from less than 1 to 4 microgm/L. The dissolved-selenium concentration and selenium discharge in the North Platte River increased in the downstream direction. The four principal tributaries that receive drainage from the Kendrick Reclamation Project contributed substantially to the increase in selenium concentration and discharge in the North Platte River. Bottom-sediment samples from the North Platte River contained selenium contents of 1.2 microgm/g or less. (Author 's abstract)

Water-Resources Investigations Report↗

USGS2020

Forest management and bats

Because more than half of the forest land in the United States is privately owned, forest landowners play an important role in the stewardship of our wildlife resources. This publication will introduce you to a group of wildlife that is particularly important to forest ecosystems, but also one of the most misunderstood: bats. We will demonstrate how active forest management can improve forest health and productivity while maintaining and enhancing habitat for these fascinating and beneficial mammals.

Report↗

USGS2014

Contaminants of emerging concern in ambient groundwater in urbanized areas of Minnesota, 2009-12

A study of contaminants of emerging concern (CECs) in ambient groundwater in urbanized areas of Minnesota was completed by the U.S. Geological Survey in cooperation with the Minnesota Pollution Control Agency. For this study, water samples were collected from November 2009 through June 2012 from 118 wells located in different land-use settings. The sampled wells primarily were screened in vulnerable sand and gravel aquifers (surficial and buried glacial aquifers) or vulnerable bedrock aquifers such as the Prairie du Chien-Jordan aquifer. Sampled well depths ranged from 9 to 285 feet below land surface. Water samples were collected by Minnesota Pollution Control Agency staff. The water samples were analyzed at U.S. Geological Survey laboratories for steroidal hormones, human-use pharmaceutical compounds, human- and animal-use antibiotics, and a broad suite of organic chemicals associated with wastewater. Reported detections were censored and not counted as detections in the data analyses if the chemical was detected in a laboratory or field blank at a similar concentration. During this study, 38 out of 127 CECs analyzed were detected among all water samples collected. Three of the detected CECs, however, were analyzed using two different analytical methods, so 35 distinct chemicals were detected. The number of detections of CECs in individual water samples ranged from 0 to 10. The three wells in proximity to landfills had the most CEC detections. One or more CECs were detected in a total of 43 samples (35 percent); no CECs were detected in 80 samples. Of the 127 CECs included for analysis in this study, 28 have established enforceable or non-enforceable health-based water-quality standards or benchmarks. Fourteen of the 35 chemicals detected in this study have established water-quality standards, whereas 21 of the chemicals detected have no established standard or benchmark. All detections in this study were less than established health-based water-quality standards, although p-cresol was detected at a concentration nearing a health-based water quality standard. Four of the six most frequently detected chemicals—azithromycin, diphenhydramine, tributyl phosphate, and lincomycin—have no health-based water-quality standards or benchmarks. The antibiotic sulfamethoxazole was the most frequently detected CEC, detected in a total of 14 of 123 samples (11.4 percent) by one or both analytical methods that include sulfamethoxazole as an analyte. Most (11 of 14, or 79 percent) of the detections of sulfamethoxazole were in samples from domestic wells or monitoring wells located in areas where septic systems or potentially leaking centralized sewers are prevalent. The chemical N,N-Diethyl-meta-toluamide (DEET) was detected at the highest concentration of any CEC, at 7.9 micrograms per liter. Bisphenol A was detected second most frequently of all chemicals. DEET and Bisphenol A were detected most frequently in wells in proximity to closed landfills. Samples from bedrock wells, most of which are drinking water wells that are deeper than glacial wells, had a higher percentage of wells with CEC detections compared to samples from wells completed in glacial aquifers. The higher dissolved oxygen concentrations and lower specific conductance for the bedrock wells sampled indicate shorter duration flow paths from the land surface to these wells than for wells completed in glacial aquifers.

Minnesota↗

USGS2007

Use of chemical analysis and assays of semipermeable membrane devices extracts to assess the response of bioavailable organic pollutants in streams to urbanization in six metropolitan areas of the United States

Studies to assess the effects of urbanization on stream ecosystems are being conducted as part of the U.S. Geological Survey’s National Water-Quality Assessment (NAWQA) Program. The overall objectives of these studies are to (1) determine how hydrologic, geomorphic, water quality, habitat, and biological characteristics respond to land-use changes associated with urbanization in specific environmental settings, and (2) compare these responses across environmental settings. As part of an integrated assessment, semipermeable membrane devices (SPMDs) were deployed in streams along a gradient of urban land-use intensity in and around Atlanta, Georgia; Raleigh-Durham, North Carolina; and Denver-Fort Collins, Colorado, in 2003; and Dallas-Fort Worth, Texas; Milwaukee-Green Bay, Wisconsin; and Portland, Oregon, in 2004. Sites were selected to avoid point-source discharge and to minimize natural variability within each of the six metropolitan areas. In addition to standard chemical analysis for hydrophobic organic contaminants, three assays were used to address mixtures and potential toxicity: (1) Fluoroscan provides an estimate of the total concentration of polycyclic aromatic hydrocarbons (PAHs); (2) the P450RGS assay indicates the presence and levels of aryl hydrocarbon receptor agonists; and (3) Microtox® measures toxicological effects on photo-luminescent bacteria. Of the 140 compounds targeted or identified by gas chromatography/mass spectrometry analysis in this study, 67 were not detected. In terms of numbers and types of compounds, the following were detected: 2 wood preservatives, 6 insecticides (parent compounds), 5 herbicides, 22 polycyclic aromatic hydrocarbons, 2 dibenzofurans, 4 polychlorinated biphenyls, 7 compounds associated with fragrances or personal care products, 4 steroids associated with wastewater, 5 polydibromated diphenyl ethers (flame retardants), 3 plasticizers, 3 antimicrobials/disinfectants, and 3 detergent metabolites. Of the 73 compounds detected and three assays utilized, 29 were detected in 25 percent or more of the streams and were strongly related to increases in urban intensity (defined as having a Spearman’s rho > 0.5 with percent urban land cover) in at least one of the six metropolitan areas investigated. These 29 endpoints included 16 PAHs, a wood preservative (pentachloroanisole), 2 insecticides (chlorpyrifos and chlordane), 3 herbicides (benfluralin, trifluralin, and dacthal), a synthetic musk (hexahydrohexamethylcyclopentabenzopyran, HHCB), 2 furans (methyldibenzofuran and benzo[b]naphtho[2,3-d]furan), and a flame retardant (BDE 47). In addition, the number of compounds detected and results of the Fluoroscan and P450RGS assays were strongly related to urban intensity. Average water concentrations estimated from SPMDs were compared to screening benchmarks for the protection of human health and aquatic life; of the 14 compounds with available benchmarks, 3 compounds (anthracene, dieldrin, and diazinon) exceeded those levels in one or more streams. Both dieldrin and anthracene exceeded their respective benchmarks in seven streams, and diazinon in only one stream. There were more exceedances in Milwaukee-Green Bay and Raleigh-Durham than in the other metropolitan areas, and there were no exceedances in Dallas-Fort Worth. The six metropolitan areas studied differed in the number and types of endpoints related to urban intensity, probably from a combination of factors governing source strength, transport, and fate of hydrophobic compounds. The number of endpoints strongly related to urban intensity ranged from 3 in Dallas-Fort Worth and Portland to 21 in Raleigh-Durham. High frequencies of detection and strong correlations with urban land cover for pyrogenic PAHs (such as unsubstituted 4-ringed PAHs) in all six metropolitan areas indicate that these compounds are an important component of urbanization, regardless of location. Pentachloroanisole, dibenzofurans, and petrogenic PAHs (alkylated PAHs and heterocyclic dibenzothiophenes) were frequently detected and strongly related to urban intensity in Atlanta, Raleigh-Durham, Milwaukee-Green Bay, and Denver-Fort Collins. Two insecticides were related to urban intensity: chlorpyrifos in Atlanta, Raleigh-Durham, and Dallas-Fort Worth; and chlordane in Raleigh-Durham. Three herbicides were strongly related to urban intensity: trifluralin in Atlanta and Raleigh-Durham; benfluralin in Atlanta, and dacthal in Denver-Fort Collins. The detection frequencies for most wastewater indicator compounds were too low to establish relations with urban intensity. Of the wastewater compounds analyzed, HHCB in Raleigh-Durham and Denver-Fort Collins, and BDE 47 in Denver-Fort Collins and Dallas-Forth Worth, had the strongest relations with urban intensity. In addition to pyrogenic PAHs, levels of aryl hydrocarbon receptor agonists (as measured by the P450RGS assay) were strongly related to increasing urban intensity in all six metropolitan areas. PAHs were the only group of aryl hydrocarbon agonists consistently detected and related with urban intensity in all six metropolitan areas. It is unknown which compounds in the SPMDs caused the increased response in the P450RGS assay because the SPMDs likely contained many aryl hydrocarbon receptor agonists not quantified by chemical analysis. It is clear that bioavailable, aryl hydrocarbon receptor agonists increase in streams with increasing urban intensity in the basin. Potential toxicity mediated by this metabolic pathway should be considered in integrated assessments of the response of aquatic biota to urbanization.

Scientific Investigations Report↗

USGS2018

Crowding affects health, growth, and behavior in headstart pens for Agassiz's desert tortoise

Worldwide, scientists have headstarted threatened and endangered reptiles to augment depleted populations. Not all efforts have been successful. For the threatened Agassiz's desert tortoise ( Gopherus agassizii ), one challenge to recovery is poor recruitment of juveniles into adult populations, and this is being addressed through headstart programs. We evaluated 8 cohorts of juvenile desert tortoises from 1 to 8 yrs old in a headstart program at Edwards Air Force Base, California, for health, behavior, and growth. We also examined capacities of the headstart pens. Of 148 juveniles evaluated for health, 99.3% were below a prime condition index; 14.9% were lethargic and unresponsive; 59.5% had protruding spinal columns and associated concave scutes; 29.1% had evidence of ant bites; and 14.2% had moderate to severe injuries to limbs or shell. Lifetime growth rates for juveniles 1–8 yrs of age were approximately two times less than growth rates reported for wild populations. Tortoises in older cohorts had higher growth rates, and models indicated that high density in pens and burrow sharing negatively affected growth rates. Densities of tortoises in pens (205–2042/ha) were 350–3500 times higher than the average density recorded in the wild (< 1/ha) for tortoises of similar sizes. The predominant forage species available to juveniles were alien annual grasses, which are nutritionally inadequate for growth. We conclude that the headstart pens were of inadequate size, likely contained too few shelters, and lacked the necessary biomass of preferred forbs to sustain the existing population. Additional factors to consider for future reptilian headstart pens include vegetative cover, food sources, soil seed banks, and soil composition.

California↗

USGS2019

Arsenic concentrations after drinking water well installation: Time-varying effects on arsenic mobilization

Chronic exposure to geogenic arsenic via drinking water is a worldwide health concern. However, effects of well installation and operation on arsenic concentrations and mobilization are not well understood. This knowledge gap impacts both reliable detection of arsenic in drinking water and effective public health recommendations to reduce exposure to arsenic. This study examines changes in arsenic and redox geochemistry over one year following installation of 254 new domestic water wells in three regions of the north-central USA that commonly have elevated arsenic concentrations. Our regions' geologic settings share some important characteristics with other high-arsenic aquifers: igneous bedrock aquifers; or late Pleistocene-age glacial sand and gravel aquifers interbedded with aquitards. Over the study, arsenic concentrations increased by 16% or more in 25% of wells in glacial aquifer regions, and the redox conditions changed towards more reducing. In wells in the bedrock region, there was no significant change in arsenic concentrations, and redox conditions changed towards more oxidizing. Our findings illustrate the importance of understanding short- to moderate-term impacts of well installation and operation on arsenic and aqueous chemistry, as it relates to human exposure. Our study informs water quality sampling requirements, which currently do not consider the implications sampling timing with respect to well installation. Evaluating arsenic concentrations in samples from new wells in the context of general regional pH and redox conditions can provide information regarding the degree of disequilibrium created by well drilling. Our analysis approach may be transferable and scalable to similar aquifer settings across the globe.

Minnesota↗

USGS2020

Microbial source tracking (MST) in Chattahoochee River National Recreation Area: Seasonal and precipitation trends in MST marker concentrations, and associations with E. coli levels, pathogenic marker presence, and land use

Escherichia coli levels in recreational waters are often used to predict when fecal-associated pathogen levels are a human health risk. The reach of the Chattahoochee River that flows through the Chattahoochee River National Recreation Area (CRNRA), located in the Atlanta-metropolitan area, is a popular recreation area that frequently exceeds the U.S. Environmental Protection Agency beach action value (BAV) for E. coli . A BacteriALERT program has been implemented to provide real-time E. coli estimates in the reach and notify the public of potentially harmful levels of fecal-associated pathogens as indicated by surrogate models based on real-time turbidity measurements from continuous water quality monitoring stations. However, E. coli does not provide information about the sources of fecal contamination and its accuracy as a human health indicator is questionable when sources of contamination are non-human. The objectives of our study were to investigate, within the Park and surrounding watersheds, seasonal and precipitation-related patterns in microbial source tracking marker concentrations of possible sources (human, dog, and ruminant), assess correlations between source contamination levels and culturable E. coli levels, determine which sources best explained model-based E. coli estimates above the BAV and detection of esp2 (a marker for the esp gene associated with pathogenic strains of Enterococcus faecium and Enterococcus faecalis) , and investigate associations between source contamination levels and land use features. Three BacteriALERT sites on the Chattahoochee River were sampled six times per season in the winter and summer from December 2015 through September 2017, and 11 additional stream sites (synoptic sites) from the CRNRA watershed were sampled once per season. Samples were screened with microbial source tracking (MST) quantitative PCR (qPCR) markers for humans (HF183 Taqman), dogs (DogBact), and ruminants (Rum2Bac), the esp2 qPCR marker, and culturable E. coli. At the BacteriALERT sites, HF183 Taqman concentrations were higher under wet conditions DogBact concentrations were greater in the winter and under wet conditions, and Rum2Bac concentrations were comparatively low throughout the study with no difference across seasons or precipitation conditions. Concentrations of HF183 Taqman, DogBact, and Rum2Bac were positively correlated with culturable E. coli concentrations; however, DogBact had the largest R 2 value among the three markers, and the forward stepwise regression indicated it was the best predictor of culturable E. coli concentrations at the BacteriALERT sites. Recursive partitioning indicated that BAV exceedances of model-based E. coli estimates were best explained by DogBact concentrations ≥3 gene copies per mL (CN/mL). Detections of esp2 at BacteriALERT sites were best explained by DogBact concentrations ≥11 CN/mL, while detections of esp2 at synoptic sites were best explained by HF183 Taqman ≥29 CN/mL. At the synoptic sites, HF183 Taqman levels were associated with wastewater treatment plant density. However, this relationship was driven primarily by a single site, suggesting possible conveyance issues in that catchment. esp2 detections at synoptic sites were positively associated with development within a 2-km radius and negatively associated with development within the catchment, suggesting multiple sources of esp2 in the watershed. DogBact and Rum2Bac were not associated with the land use features included in our analyses. Implications for Park management include: 1) fecal contamination levels were highest during wet conditions and in the off season when fewer visitors are expected to be participating in water-based recreation, 2) dogs are likely contributors to fecal contamination in the CRNRA and may be sources of pathogenic bacteria indicating further investigation of the origins of this contamination may be warranted as would be research to understand the human health risks from exposure to dog fecal contamination, and 3) high levels of the human marker at one site in the CRNRA watershed suggests more extensive monitoring in that catchment may locate the origin of human fecal contamination detected during this study.

Georgia↗

USGS2019

Artificial intelligence and avian influenza: Using machine learning to enhance active surveillance for avian influenza viruses

Influenza A viruses are one of the most significant viral groups globally with substantial impacts on human, domestic animal and wildlife health. Wild birds are the natural reservoirs for these viruses, and active surveillance within wild bird populations provides critical information about viral evolution forming the basis of risk assessments and countermeasure development. Unfortunately, active surveillance programs are often resource‐intensive, and thus, enhancing programs for increased efficiency is paramount. Machine learning, a branch of artificial intelligence applications, provides statistical learning procedures that can be used to gain novel insights into disease surveillance systems. We use a form of machine learning, gradient boosted trees, to estimate the probability of isolating avian influenza viruses (AIV) from wild bird samples collected during surveillance for AIVs from 2006 to 2011 in the United States. We examined several predictive features including age, sex, bird type, geographic location and matrix gene rRT‐PCR results. Our final model had high predictive power and only included geographic location and rRT‐PCR results as important predictors. The highest predicted viral isolation probability was for samples collected from the north‐central states and the south‐eastern region of Alaska. Lower rRT‐PCR Ct‐values are associated with increased likelihood of AIV isolation, and the model estimated 16% probability of isolating AIV from samples declared negative (i.e., ≥35 Ct‐value) using the rRT‐PCR screening test and standard protocols. Our model can be used to prioritize previously collected samples for isolation and rapidly evaluate AIV surveillance designs to maximize the probability of viral isolation given limited resources and laboratory capacity.

Transboundary and Emerging Diseases↗

USGS1994

U.S. Geological Survey yearbook, fiscal year 1993: At work across the Nation

The need for earth science has never been more paramount. The devastating flooding of the Mississippi River this past year, strikingly portrayed on the cover and discussed in detail in this report (p. 37-42), was a sobering reminder of nature's elemental power. As a Nation, we face many environmental and economic challenges, such as natural hazards, that can be addressed effectively only through science. Water quality, resource assessments, climate change, and toxic wastes are all critical issues that can best be dealt with when approached from a sound scientific base. The goal of the U.S. Geological Survey is to provide hydrologic, geologic, and topographic information and understanding that contribute to the wise management of the Nation's natural resources and that promote the health, safety, and well-being of all Americans. FY1993 has proven to be a particularly challenging one for the USGS. We entered into a time of transition from the long-term leadership of Director Dallas Peck and Associate Director Doyle Frederick to the appointment of a new director. We thank Dallas and Doyle for their many years of service and for their support during the transition.

Yearbook↗

USGS2000

Organochlorine compounds in streambed sediment and in biological tissue from streams and their relations to land use, central Arizona

Streambed-sediment samples from 13 sites and biological-tissue samples from 11 sites in the Gila River Basin in central Arizona were analyzed for 32 organochlorine compounds in streambed sediment and 28 compounds in biological tissue during 1996 as part of the U.S. Geological Survey's National Water-Quality Assessment program. The objectives of the study were to determine the occurrence and distribution of organochlorine compounds and their relation to land use. Sampling sites were categorized on the basis of major land uses in the basin or the source of water in the stream. Because land uses were mixed or had changed over time, some land-use categories were combined. Sites were categorized as forest/rangeland (6), forest/urban (1), urban (4), or agricultural/urban (2). Thirteen organochlorine compounds were detected in streambed-sediment samples, and 10 were detected in tissue samples. The number of compounds found in streambed-sediment samples from individual sites ranged from 0 to 10, and the range for individual tissue samples was 0 to 7. Comparison of the number of detections in streambed-sediment samples to the number of detections in tissue samples from particular sites where both were sampled yielded five instances where more compounds were detected in streambed sediment, six instances where more compounds were detected in tissue, and five instances where the number of detections in streambed sediment and tissue were equal. The frequency of detection of particular compounds for sites where both streambed sediment and tissue were sampled resulted in five compounds being detected more frequently in streambed sediment, five more frequently in tissue, and three compounds that were equally frequent in streambed sediment and in tissue. Few contaminants were detected in samples from the forest/rangeland sites; greater numbers of compounds were detected at the urban sites and at the forest/urban site. The greatest number of compounds and the highest concentrations of many contaminants were detected at agriculture/urban sites. The compound detected most frequently in streambed-sediment and tissue samples was p,p'-DDE. Streambed-sediment guideline values for the protection of aquatic life for p,p'-DDE and total DDT were exceeded at both agricultural/urban sites, The streambed-sediment guideline value for the protection of aquatic life for total chlordane was exceeded at one agricultural/urban site, one urban site, and the forest/urban site. The streambed-sediment guideline value for the protection of aquatic life for total PCB’s was exceeded at one agricultural/urban site. Guideline values for the protection of fish-eating wildlife for total DDT and for toxaphene were exceeded only in samples from the two agricultural/urban sites. The guideline value for the protection of fish-eating wildlife for total PCB’s was equaled or exceeded in samples from two sites—one urban and one agricultural/urban site. Screening values established by the U.S. Environmental Protection Agency for the protection of human health for edible portions of fish were exceeded by total DDT and by toxaphene in fish-tissue samples from both agricultural/urban sites. The human-health criterion for total PCB’s was exceeded in two fish-tissue samples from an agricultural site and from an urban site. Tissue samples analyzed in this study were for whole fish, and thus, concentration data are not entirely comparable to the screening values of the U.S. Environmental Protection Agency. Because these exceedences were an order of magnitude above the criteria, however, it is possible that concentrations in the edible portions of fish from these locations could present a human- health risk. Analyses of samples of edible portions of fish from these locations would be needed to adequately assess the presence or absence of a human-health risk. The similarity of the results of this study to the results of other studies of organochlorine compounds in the environment suggests that there is a correlation between contaminants in sediment and biological-tissue samples and land uses. As with other studies of the occurrence and distribution of organochlorine contaminants in streambed sediments and biological tissue, this study shows that many organochlorine compounds continue to persist in the environment and thus could pose a threat to aquatic life, fish-eating wildlife, and possibly to humans who consume contaminated fish.

Arizona↗

USGS2017

Nutrient and pesticide contamination bias estimated from field blanks collected at surface-water sites in U.S. Geological Survey Water-Quality Networks, 2002–12

Potential contamination bias was estimated for 8 nutrient analytes and 40 pesticides in stream water collected by the U.S. Geological Survey at 147 stream sites from across the United States, and representing a variety of hydrologic conditions and site types, for water years 2002–12. This study updates previous U.S. Geological Survey evaluations of potential contamination bias for nutrients and pesticides. Contamination is potentially introduced to water samples by exposure to airborne gases and particulates, from inadequate cleaning of sampling or analytic equipment, and from inadvertent sources during sample collection, field processing, shipment, and laboratory analysis. Potential contamination bias, based on frequency and magnitude of detections in field blanks, is used to determine whether or under what conditions environmental data might need to be qualified for the interpretation of results in the context of comparisons with background levels, drinking-water standards, aquatic-life criteria or benchmarks, or human-health benchmarks. Environmental samples for which contamination bias as determined in this report applies are those from historical U.S. Geological Survey water-quality networks or programs that were collected during the same time frame and according to the same protocols and that were analyzed in the same laboratory as field blanks described in this report. Results from field blanks for ammonia, nitrite, nitrite plus nitrate, orthophosphate, and total phosphorus were partitioned by analytical method; results from the most commonly used analytical method for total phosphorus were further partitioned by date. Depending on the analytical method, 3.8, 9.2, or 26.9 percent of environmental samples, the last of these percentages pertaining to all results from 2007 through 2012, were potentially affected by ammonia contamination. Nitrite contamination potentially affected up to 2.6 percent of environmental samples collected between 2002 and 2006 and affected about 3.3 percent of samples collected between 2007 and 2012. The percentages of environmental samples collected between 2002 and 2011 that were potentially affected by nitrite plus nitrate contamination were 7.3 for samples analyzed with the low-level method and 0.4 for samples analyzed with the standard-level method. These percentages increased to 14.8 and 2.2 for samples collected in 2012 and analyzed using replacement low- and standard-level methods, respectively. The maximum potentially affected concentrations for nitrite and for nitrite plus nitrate were much less than their respective maximum contamination levels for drinking-water standards. Although contamination from particulate nitrogen can potentially affect up to 21.2 percent and that from total Kjeldahl nitrogen can affect up to 16.5 percent of environmental samples, there are no critical or background levels for these substances. For total nitrogen, orthophosphate, and total phosphorus, contamination in a small percentage of environmental samples might be consequential for comparisons relative to impairment risks or background levels. At the low ends of the respective ranges of impairment risk for these nutrients, contamination in up to 5 percent of stream samples could account for at least 23 percent of measured concentrations of total nitrogen, for at least 40 or 90 percent of concentrations of orthophosphate, depending on the analytical method, and for 31 to 76 percent of concentrations of total phosphorus, depending on the time period. Twenty-six pesticides had no detections in field blanks. Atrazine with 12 and metolachlor with 11 had the highest number of detections, mostly occurring in spring or early summer. At a 99-percent level of confidence, contamination was estimated to be no greater than the detection limit in at least 98 percent of all samples for 38 of 40 pesticides. For metolachlor and atrazine, potential contamination was no greater than 0.0053 and 0.0093 micrograms per liter in 98 percent of samples. For 11 of 14 pesticides with at least one detection, the maximum potentially affected concentration of the environmental sample was less than their respective human-health or aquatic-life benchmarks. Small percentages of environmental samples had concentrations high enough that atrazine contamination potentially could account for the entire aquatic-life benchmark for acute effects on nonvascular plants, that dieldrin contamination could account for up to 100 percent of the cancer health-based screening level, or that chlorpyrifos contamination could account for 13 or 12 percent of the concentrations in the aquatic-life benchmarks for chronic effects on invertebrates or the criterion continuous concentration for chronic effects on aquatic life.

Scientific Investigations Report↗

USGS2019

State of knowledge on current exposure, fate and potential health effects of contaminants in polar bears from the circumpolar Arctic

The polar bear ( Ursus maritimus ) is among the Arctic species exposed to the highest concentrations of long-range transported bioaccumulative contaminants, such as halogenated organic compounds and mercury. Contaminant exposure is considered to be one of the largest threats to polar bears after the loss of their Arctic sea ice habitat due to climate change. The aim of this review is to provide a comprehensive summary of current exposure, fate, and potential health effects of contaminants in polar bears from the circumpolar Arctic required by the Circumpolar Action Plan for polar bear conservation. Overall results suggest that legacy persistent organic pollutants (POPs) including polychlorinated biphenyls, chlordanes and perfluorooctane sulfonic acid (PFOS), followed by other perfluoroalkyl compounds (e.g. carboxylic acids, PFCAs) and brominated flame retardants, are still the main compounds in polar bears. Concentrations of several legacy POPs that have been banned for decades in most parts of the world have generally declined in polar bears. Current spatial trends of contaminants vary widely between compounds and recent studies suggest increased concentrations of both POPs and PFCAs in certain subpopulations. Correlative field studies, supported by in vitro studies, suggest that contaminant exposure disrupts circulating levels of thyroid hormones and lipid metabolism, and alters neurochemistry in polar bears. Additionally, field and in vitro studies and risk assessments indicate the potential for adverse impacts to polar bear immune functions from exposure to certain contaminants.

Science of Total Environment↗

USGS2008

Distribution of Elevated Nitrate Concentrations in Ground Water in Washington State

More than 60 percent of the population of Washington State uses ground water for their drinking and cooking needs. Nitrate concentrations in ground water are elevated in parts of the State as a result of various land-use practices, including fertilizer application, dairy operations and ranching, and septic-system use. Shallow wells generally are more vulnerable to nitrate contamination than deeper wells (Williamson and others, 1998; Ebbert and others, 2000). In order to protect public health, the Washington State Department of Health requires that public water systems regularly measure nitrate in their wells. Public water systems serving more than 25 people collect water samples at least annually; systems serving from 2 to 14 people collect water samples at least every 3 years. Private well owners serving one residence may be required to sample when the well is first drilled, but are unregulated after that. As a result, limited information is available to citizens and public health officials about potential exposure to elevated nitrate concentrations for people whose primary drinking-water sources are private wells. The U.S. Geological Survey and Washington State Department of Health collaborated to examine water-quality data from public water systems and develop models that calculate the probability of detecting elevated nitrate concentrations in ground water. Maps were then developed to estimate ground water vulnerability to nitrate in areas where limited data are available.

Fact Sheet↗

USGS2010

Climate change and wildlife health: direct and indirect effects

Climate change will have significant effects on the health of wildlife, domestic animals, and humans, according to scientists. The Intergovernmental Panel on Climate Change projects that unprecedented rates of climate change will result in increasing average global temperatures; rising sea levels; changing global precipitation patterns, including increasing amounts and variability; and increasing midcontinental summer drought (Intergovernmental Panel on Climate Change, 2007). Increasing temperatures, combined with changes in rainfall and humidity, may have significant impacts on wildlife, domestic animal, and human health and diseases. When combined with expanding human populations, these changes could increase demand on limited water resources, lead to more habitat destruction, and provide yet more opportunities for infectious diseases to cross from one species to another. Awareness has been growing in recent years about zoonotic diseases— that is, diseases that are transmissible between animals and humans, such as Lyme disease and West Nile virus. The rise of such diseases results from closer relationships among wildlife, domestic animals, and people, allowing more contact with diseased animals, organisms that carry and transmit a disease from one animal to another (vectors), and people. Disease vectors include insects, such as mosquitoes, and arachnids, such as ticks. Thus, it is impossible to separate the effects of global warming on wildlife from its effects on the health of domestic animals or people. Climate change, habitat destruction and urbanization, the introduction of exotic and invasive species, and pollution—all affect ecosystem and human health. Climate change can also be viewed within the context of other physical and climate cycles, such as the El Niño Southern Oscillation (El Niño), the North Atlantic Oscillation, and cycles in solar radiation that have profound effects on the Earth’s climate. The effects of climate change on wildlife disease are summarized in several areas of scientific study discussed briefly below: geographic range and distribution of wildlife diseases, plant and animal phenology (Walther and others, 2002), and patterns of wildlife disease, community and ecosystem composition, and habitat degradation.

Fact Sheet↗

USGS2011

Largemouth bass (Micropterus salmoides) and striped mullet (Mugil cephalus) as vectors of contaminants to human consumers in northwest Florida

The health benefits of regular consumption of fish and seafood have been espoused for many years. However, fish are also a potential source of environmental contaminants that have well known adverse effects on human health. We investigated the consumption risks for largemouth bass ( Micropterus salmoides ; n = 104) and striped mullet ( Mugil cephalus ; n = 170), two commonly harvested and consumed fish species inhabiting fresh and estuarine waters in northwest Florida. Skinless fillets were analyzed for total mercury, inorganic arsenic, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F), polychlorinated biphenyls (PCBs), and organochlorine pesticides. Contaminant levels were compared to screening values (SV) calculated using U.S. Environmental Protection Agency (EPA) recommendations for establishing consumption advisories. Largemouth bass were found to contain high levels of total mercury at all sampling locations (0.37–0.89 ug/g) and one location exhibited elevated total PCBs (39.4 ng/g). All of the samples exceeded Florida fish consumption advisory trigger levels for total mercury and one location exceeded the U.S. EPA SV for total PCBs. As a result of the high mercury levels, the non-cancer health risks (hazard index–HI) for bass were above 1 for all locations. Striped mullet from several locations with known point sources contained elevated levels of PCBs (overall range 3.4–59.3 ng/g). However, total mercury levels in mullet were low. Eight of the 16 mullet sampling locations exceeded the U.S. EPA SV for total PCBs and two locations exceeded an HI of 1 due to elevated PCBs. Despite the elevated levels of total PCBs in some samples, only two locations exceeded the acceptable cancer risk range and therefore cancer health risks from consumption of bass and mullet were determined to be low at most sampling locations.

Florida↗