Geology topics

Paul M. Bradley

Publications and source records attributed to Paul M. Bradley.

At least 73 records · Page 4Linked to original sources

USGS2018

Potential toxicity of complex mixtures in surface waters from a nationwide survey of United States streams: Identifying in vitro bioactivities and causative chemicals

While chemical analysis of contaminant mixtures remains an essential component of environmental monitoring, bioactivity-based assessments using in vitro systems increasingly play a role in the detection of biological effects. Historically, in vitro assessments focused on a few biological pathways, e.g., aryl hydrocarbon receptor (AhR) or estrogen receptor (ER) activities. High-throughput screening (HTS) technologies have greatly increased the number of biological targets and processes that can be rapidly assessed. Here we screened extracts of surface waters from nationwide survey of United States (US) streams for bioactivities associated with 69 different endpoints using two multiplexed HTS assays. Bioactivity of extracts from 38streams was evaluated and compared with concentrations of over 700 analytes to identify chemicals contributing to observed effects. Eleven primary biological endpoints were detected. Pregnane X receptor and AhR-mediated activities were the most commonly detected. Measured chemicals did not completely account for AhR and PXR responses. Surface waters with AhR and PXR effects were associated with low intensity, developed land-cover. Likewise, elevated bioactivities frequently associated with wastewater discharges included endocrine related endpoints— ER and glucocorticoid receptor (GR). These results underscore the value of bioassay-based monitoring of environmental mixtures for detecting biological effects that could not be ascertained solely through chemical analyses.

Environmental Science & Technology↗

USGS2018

Reconnaissance of mixed organic and inorganic chemicals in private and public supply tapwaters at selected residential and workplace sites in the United States

Safe drinking water at the point-of-use (tapwater, TW) is a United States public health priority. Multiple lines of evidence were used to evaluate potential human health concerns of 482 organics and 19 inorganics in TW from 13 (7 public supply, 6 private well self-supply) home and 12 (public supply) workplace locations in 11 states. Only uranium (61.9 μg L –1 , private well) exceeded a National Primary Drinking Water Regulation maximum contaminant level (MCL: 30 μg L –1 ). Lead was detected in 23 samples (MCL goal: zero). Seventy-five organics were detected at least once, with median detections of 5 and 17 compounds in self-supply and public supply samples, respectively (corresponding maxima: 12 and 29). Disinfection byproducts predominated in public supply samples, comprising 21% of all detected and 6 of the 10 most frequently detected. Chemicals designed to be bioactive (26 pesticides, 10 pharmaceuticals) comprised 48% of detected organics. Site-specific cumulative exposure–activity ratios (∑ EAR ) were calculated for the 36 detected organics with ToxCast data. Because these detections are fractional indicators of a largely uncharacterized contaminant space, ∑ EAR in excess of 0.001 and 0.01 in 74 and 26% of public supply samples, respectively, provide an argument for prioritized assessment of cumulative effects to vulnerable populations from trace-level TW exposures.

Environmental Science & Technology↗

USGS2018

Concentrations of lead and other inorganic constituents in samples of raw intake and treated drinking water from the municipal water filtration plant and residential tapwater in Chicago, Illinois, and East Chicago, Indiana, July–December 2017

The U.S. Geological Survey (USGS) Environmental Health Mission Area (EHMA) is providing comprehensive science on sources, movement, and transformation of contaminants and pathogens in watershed and aquifer drinking-water supplies and in built water and wastewater infrastructure (referred to as the USGS Water and Wastewater Infrastructure project) in the Greater Chicago Area and elsewhere in the United States, to fill data gaps identified by stakeholders and collaborators in drinking water and public health. EHMA Water and Wastewater Infrastructure research specifically provides insight into natural factors in the environment as well as those water-infrastructure components and processes (such as source-water corrosivity, treatment, plumbing, and so forth) that might influence human exposure to chemical and microbial contaminants at the residential tap. This infrastructure-exposure research role is fulfilled uniquely by the USGS and not by the U.S. Environmental Protection Agency (EPA), other agencies, or municipalities that focus on regulatory and policy activities and related compliance. The USGS approach to assessing the possible links between human health and chemical contaminant and pathogen exposure in drinking water is conducted in collaboration with public health experts and includes comprehensive characterization of the presence/absence and concentrations of more than 500 organic and 27 inorganic chemical constituents at the point of use (tap). Laboratory results for lead and other inorganic contaminants in Chicago, Illinois, and East Chicago, Indiana, residential tapwater are being released to ensure the timely release of quality-assured data to participants in the study. Concentrations of lead and other inorganic constituents were assessed in drinking water at the point of use (kitchen tap or filter) in 45 residential locations and in two locations within each of the two Chicago water purification plants and the two East Chicago water filtration plants during July–December 2017. Three methods were used for analyzing lead. The most sensitive method had a reporting limit of 0.020 micrograms per liter (µg/L). When using the most sensitive analytical method, lead was detected in 39 of 45 residential tapwater samples, with concentrations ranging from less than 0.020 µg/L to 5.31 µg/L (median of the detected values = 0.481 µg/L). Concentrations of lead also were detected in Lake Michigan intake water at all water purification/filtration plant facilities at concentrations ranging from 0.083 to 0.330 µg/L, but were not detected above the reporting limit in any samples of treated, pre-distribution drinking water at any of the water purification/filtration plant facilities. Because the USGS Water and Wastewater Infrastructure project in the Greater Chicago Area is focused on the potential human exposure to a broad suite of organic and inorganic contaminants in drinking water and is not focused specifically on lead, the sampling protocol did not include “first-draw,” stagnant sampling and samples were collected with point-of-use treatment in place, if present. Thus, the lead results reported herein are not appropriate for assessment of compliance with the EPA 1991 Lead and Copper Rule. Information resources for lead mitigation and water filtration are provided.

Illinois, Indiana↗

USGS2018

Methods used for the collection and analysis of chemical and biological data for the Tapwater Exposure Study, United States, 2016–17

In 2016, the U.S. Geological Survey (USGS) Environmental Health Mission Area, initiated the Tapwater Exposure Study as part of an infrastructure project to assess human exposure to potential threats from complex mixtures of contaminants. In the pilot phase (2016), samples were collected from 11 States throughout the United States, and in the second phase (2017), the study focused on the Greater Chicago area, including North and South Chicago, Illinois, and East Chicago, Indiana. Residential tapwater samples were collected at private residences during both phases, and during the first phase, samples were collected from Federal office buildings and from one office 19-liter water-bottle source. During the second phase, raw intake and treated (pre-distributional) water samples also were collected from four drinking-water treatment facilities in the Greater Chicago area. Samples were sent to laboratories at the USGS, U.S. Environmental Protection Agency, National Institute of Environmental Health Sciences, and Colorado School of Mines Center for Environmental Risk Assessment, for potential drinking-water pathogens, chemical, and bioassay analyses. These analyses included more than 400 chemicals such as trace elements, steroid hormones, pharmaceuticals, volatile organic compounds, pesticides, per- and polyfluorinated alkyl substances, cyanotoxins, and other organic compounds. The in vitro bioassay analyses included estrogen, androgen, and glucocorticoid receptor activity.

Open-File Report↗

USGS2018

Nutrient enrichment in wadeable urban streams in the piedmont ecoregion of the southeastern United States

The U.S. Geological Survey (USGS) Southeastern Stream Quality Assessment (SESQA) collected weekly samples for nitrogen and phosphorus in 76 wadeable streams in the urbanized Piedmont ecoregion of the Southeastern United States, during April–June 2014. Total nitrogen (TN) concentrations in excess of EPA guidelines and statistically greater than at reference locations indicated nitrogen-nutrient enrichment in streams draining poultry confined animal feeding operations (CAFO) or urban centers. Nitrate plus nitrite (NO3 + NO2) dominated TN species in urban/CAFO-influenced streams. Streams that drained poultry CAFO and Washington DC had statistically higher NO3 + NO2 concentrations than streams draining Atlanta, Charlotte, Greenville, or Raleigh. In contrast, total phosphorus (TP) concentrations in Atlanta and Washington DC streams statistically were comparable to and lower than, respectively, reference stream concentrations. Over 50% of TP concentrations in Greenville, Charlotte, Raleigh and CAFO-influenced streams exceeded the EPA guideline and reference location mean concentrations, indicating phosphorus-nutrient enrichment. Urban land use, permitted point sources, and soil infiltration metrics best predicted TN exceedances. Elevated TN and NO3 + NO2 concentrations in urban streams during low flow were consistent with reduced in-stream dilution of point-source or groundwater contributions. Urban land use, permitted point sources, and surface runoff metrics best predicted TP exceedances. Elevated TP in CAFO and urban streams during high flow were consistent with non-point sources and particulate transport.

Piedmont Ecoregion↗

USGS2018

Bioactive contaminants of emerging concern in National Park waters of the northern Colorado Plateau, USA

Pharmaceuticals and personal care products (PPCPs), wastewater indicators (WWIs), and pesticides (herein, Contaminants of Emerging Concern [CECs]) have been documented in surface waters throughout the world and have associated risks to aquatic life. While much research has focused on temperate and urbanized watersheds, less is known about CEC presence in semi-arid landscapes, where water availability is limited and populations are low. CEC presence in water and sediment is reported for 21 sites in eight U.S. national parks in the northern Colorado Plateau region. From 2012 to 2016, at least one PPCP and/or WWI was detected at most sites on over half of sampling visits, indicating that CECs are not uncommon even in isolated areas. CEC detections were generally fewer and at lower concentrations than in urbanized or agricultural watersheds. Consistent with studies from other U.S. regions, the most frequently detected CECs in this study include DEET, caffeine, organophosphorus flame retardants, and bisphenol A in water and fecal indicators and polycyclic aromatic hydrocarbons in sediment. Maximum concentrations in this study were generally below available water quality benchmarks, sediment quality guidelines, and risk assessment thresholds associated with vertebrates. Additional work is needed to assess the potential activity of hormones, which had high reporting limits in our study, and potential bioactivity of environmental concentrations for invertebrates, microbial communities, and algae. Potential sources of CEC contamination include upstream wastewater effluent discharges and National Park Service invasive-plant-control herbicide applications. CEC occurrence patterns and similarities between continuous and isolated flow locations suggest that direct contamination from individual visitors may also occur. While our data indicate there is little aquatic health risk associated with CECs at our sites, our results demonstrate the ubiquity of CECs on the landscape and a continued need for public outreach concerning resource-use ethics and the potential effects of upstream development.

Colorado Plateau↗

USGS2018

Pharmaceuticals, hormones, pesticides, and other bioactive contaminants in water, sediment, and tissue from Rocky Mountain National Park, 2012–2013

Pharmaceuticals, hormones, pesticides, and other bioactive contaminants (BCs) are commonly detected in surface water and bed sediment in urban and suburban areas, but these contaminants are understudied in remote locations. In Rocky Mountain National Park (RMNP), Colorado, USA, BCs may threaten the reproductive success and survival of native aquatic species, benthic communities, and pelagic food webs. In 2012–2013, 67 water, 57 sediment, 63 fish, 10 frog, and 12 quality-control samples (8 water and 4 sediment) were collected from 20 sites in RMNP. Samples were analyzed for 369 parameters including 149 pharmaceuticals, 22 hormones, 137 pesticides, and 61 other chemicals or conditions to provide a representative assessment of BC occurrence within RMNP. Results indicate that BCs were detected in water and/or sediment from both remote and more accessible locations in RMNP. The most commonly detected BCs in water were caffeine, camphor, para-cresol, and DEET; and the most commonly detected BCs in sediment were indole, 3-methyl-1H-indole, para-cresol, and 2,6-dimethyl-naphthalene. Some detected contaminants, including carbaryl, caffeine, and oxycodone, are clearly attributable to direct local human input, whereas others may be transported into the park atmospherically (e.g., atrazine) or have local natural sources (e.g., para-cresol). One or more pharmaceuticals were detected in at least 1 sample from 15 of 20 sites. Most of the 29 detected pharmaceuticals are excreted primarily in human urine, not feces. Elevated net estrogenicity was observed in 18% of water samples, and elevated vitellogenin in blood was observed in 12% of male trout, both evidence of potential endocrine disruption. Hormone concentrations in sediment tended to be greater than concentrations in water. Most BCs were observed at concentrations below those not expected to pose adverse effects to aquatic life. Results indicate that even in remote locations aquatic wildlife can be exposed to pharmaceuticals, hormones, pesticides, and other bioactive contaminants.

Colorado↗

USGS2018

Contaminants of emerging concern in the environment: Where we have been and what does the future hold?

In 1962, Rachel Carson’s book Silent Spring alerted the nation to the dangers of manmade chemicals and indiscriminate use of pesticides. DDT was the culprit and its use threatened a variety of wildlife, including the national bird, bald eagles. In 1969, pressured by scientists and the public, the United States banned almost all uses of DDT; however, DDT was just the tip of the chemical iceberg. In 1996, Theo Colborn’s book, Our Stolen Future, again alerted the public to the dangers of chemical exposure. Endocrine-disrupting chemicals were identified as concerns because exposure to extremely small concentrations can have adverse effects on people and wildlife by interfering with chemical messaging systems, affecting things like sexual development and reproduction.

Water Resources Impact↗

USGS2017

Widespread occurrence and potential for biodegradation of bioactive contaminants in Congaree National Park, USA

Organic contaminants with designed molecular bioactivity, such as pesticides and pharmaceuticals, originate from human and agricultural sources, occur frequently in surface waters, and threaten the structure and function of aquatic and terrestrial ecosystems. Congaree National Park in South Carolina (USA) is a vulnerable park unit due to its location downstream of multiple urban and agricultural contaminant sources and its hydrologic setting, being composed almost entirely of floodplain and aquatic environments. Seventy-two water and sediment samples were collected from 16 sites in Congaree National Park during 2013 to 2015, and analyzed for 199 and 81 targeted organic contaminants, respectively. More than half of these water and sediment analytes were not detected or potentially had natural sources. Pharmaceutical contaminants were detected (49 total) frequently in water throughout Congaree National Park, with higher detection frequencies and concentrations at Congaree and Wateree River sites, downstream from major urban areas. Forty-seven organic wastewater indicator chemicals were detected in water, and 36 were detected in sediment, of which approximately half are distinctly anthropogenic. Endogenous sterols and hormones, which may originate from humans or wildlife, were detected in water and sediment samples throughout Congaree National Park, but synthetic hormones were detected only once, suggesting a comparatively low risk of adverse impacts. Assessment of the biodegradation potentials of 8 14 C-radiolabeled model contaminants indicated poor potentials for some contaminants, particularly under anaerobic sediments conditions.

South Carolina↗

USGS2017

Occurrence and in vitro bioactivity of estrogen, androgen, and glucocorticoid compounds in a nationwide screen of United States stream waters

In vitro bioassays are sensitive, effect-based tools used to quantitatively screen for chemicals with nuclear receptor activity in environmental samples. We measured in vitro estrogen (ER), androgen (AR), and glucocorticoid receptor (GR) activity, along with a broad suite of chemical analytes, in streamwater from 35 well-characterized sites (3 reference and 32 impacted) across 24 states and Puerto Rico. ER agonism was the most frequently detected with nearly all sites (34/35) displaying activity (range, 0.054–116 ng E2Eq L –1 ). There was a strong linear relationship ( r 2 = 0.917) between in vitro ER activity and concentrations of steroidal estrogens after correcting for the in vitro potency of each compound. AR agonism was detected in 5/35 samples (range, 1.6–4.8 ng DHTEq L –1 ) but concentrations of androgenic compounds were largely unable to account for the in vitro activity. Similarly, GR agonism was detected in 9/35 samples (range, 6.0–43 ng DexEq L –1 ); however, none of the recognized GR-active compounds on the target-chemical analyte list were detected. The utility of in vitro assays in water quality monitoring was evident from both the quantitative agreement between ER activity and estrogen concentrations, as well as the detection of AR and GR activity for which there were limited or no corresponding target-chemical detections to explain the bioactivity. Incorporation of in vitro bioassays as complements to chemical analyses in standard water quality monitoring efforts would allow for more complete assessment of the chemical mixtures present in many surface waters.

Environmental Science & Technology↗

USGS2017

Expanded target-chemical analysis reveals extensive mixed-organic-contaminant exposure in USA streams

Surface water from 38 streams nationwide was assessed using 14 target-organic methods (719 compounds). Designed-bioactive anthropogenic contaminants (biocides, pharmaceuticals) comprised 57% of 406 organics detected at least once. The 10 most-frequently detected anthropogenic-organics included eight pesticides (desulfinylfipronil, AMPA, chlorpyrifos, dieldrin, metolachlor, atrazine, CIAT, glyphosate) and two pharmaceuticals (caffeine, metformin) with detection frequencies ranging 66–84% of all sites. Detected contaminant concentrations varied from less than 1 ng L –1 to greater than 10 μg L –1 , with 77 and 278 having median detected concentrations greater than 100 ng L –1 and 10 ng L –1 , respectively. Cumulative detections and concentrations ranged 4–161 compounds (median 70) and 8.5–102 847 ng L –1 , respectively, and correlated significantly with wastewater discharge, watershed development, and toxic release inventory metrics. Log 10 concentrations of widely monitored HHCB, triclosan, and carbamazepine explained 71–82% of the variability in the total number of compounds detected (linear regression; p -values: < 0.001–0.012), providing a statistical inference tool for unmonitored contaminants. Due to multiple modes of action, high bioactivity, biorecalcitrance, and direct environment application (pesticides), designed-bioactive organics (median 41 per site at μg L –1 cumulative concentrations) in developed watersheds present aquatic health concerns, given their acknowledged potential for sublethal effects to sensitive species and lifecycle stages at low ng L –1 .

Environmental Science & Technology↗

USGS2017

Methods used to characterize the chemical composition and biological activity of environmental waters throughout the United States, 2012-14

A vast array of chemical compounds are in wide commercial use in the United States, and the potential ecological and human-health effect of exposure to chemical mixtures has been identified as a high priority in environment health science. Awareness of the potential effects of low-level chemical exposures is rising. The U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, conducted a study in which samples were collected from 38 streams in 25 States to provide an overview of contaminants found in stream water across the Nation. Additionally, biological screening assays were used to help determine any potential ecological and human-health effects of these chemical mixtures and to prioritize target chemicals for future toxicological studies. This report describes the site locations and the sampling and analytical methods and quality-assurance procedures used in the study.

Open-File Report↗

USGS2016

Metformin and other pharmaceuticals widespread in wadeable streams of the southeastern United States

Pharmaceutical contaminants are growing aquatic-health concerns and largely attributed to wastewater treatment facility (WWTF) discharges. Five biweekly water samples from 59 small Piedmont (United States) streams were analyzed for 108 pharmaceuticals and degradates using high-performance liquid chromatography and tandem mass spectrometry. The antidiabetic metformin was detected in 89% of samples and at 97% of sites. At least one pharmaceutical was detected at every site (median of 6, maximum of 45), and several were detected at ≥10% of sites at concentrations reported to affect multiple aquatic end points. Maximal cumulative (all detected compounds) concentrations per site ranged from 17 to 16000 ng L –1 . Watershed urbanization, water table depth, soil thickness, and WWTF metrics correlated significantly with in-stream pharmaceutical contamination. Comparable pharmaceutical concentrations and detections at sites with and without permitted wastewater discharges demonstrate the importance of non-WWTF sources and the need for broad-scale mitigation. The results highlight a fundamental biochemical link between global human-health crises like diabetes and aquatic ecosystem health.

Environmental Science & Technology Letters↗

USGS2016

Effect of wastewater treatment facility closure on endocrine disrupting chemicals in a Coastal Plain stream

Wastewater treatment facility (WWTF) closures are rare environmental remediation events; offering unique insight into contaminant persistence, long-term wastewater impacts, and ecosystem recovery processes. The U.S. Geological Survey assessed the fate of select endocrine disrupting chemicals (EDC) in surface water and streambed sediment one year before and one year after closure of a long-term WWTF located within the Spirit Creek watershed at Fort Gordon, Georgia. Sample sites included a WWTF-effluent control located upstream from the outfall, three downstream effluent-impacted sites located between the outfall and Spirit Lake, and one downstream from the lake's outfall. Prior to closure, the 2.2-km stream segment downstream from the WWTF outfall was characterized by EDC concentrations significantly higher ( α = 0.05) than at the control site; indicating substantial downstream transport and limited in-stream attenuation of EDC, including pharmaceuticals, estrogens, alkylphenol ethoxylate (APE) metabolites, and organophosphate flame retardants (OPFR). Wastewater-derived pharmaceutical, APE metabolites, and OPFR compounds were also detected in the outflow of Spirit Lake, indicating the potential for EDC transport to aquatic ecosystems downstream of Fort Gordon under effluent discharge conditions. After the WWTF closure, no significant differences in concentrations or numbers of detected EDC compounds were observed between control and downstream locations. The results indicated EDC pseudo-persistence under preclosure, continuous supply conditions, with rapid attenuation following WWTF closure. Low concentrations of EDC at the control site throughout the study and comparable concentrations in downstream locations after WWTF closure indicated additional, continuing, upstream contaminant sources within the Spirit Creek watershed. 

Georgia↗

USGS2016

Hydraulic and biochemical gradients limit wetland mercury supply to an Adirondack stream

Net fluxes (change between upstream and downstream margins) for water, methylmercury (MeHg), total mercury (THg), dissolved organic carbon (DOC), and chloride (Cl) were assessed twice in an Adirondack stream reach (Sixmile Brook, USA), to test the hypothesized importance of wetland-stream hydraulic and chemical gradients as fundamental controls on fluvial mercury (Hg) supply. The 500 m study reach represented less than 4% of total upstream basin area. During a snowmelt high-flow event in May 2009 surface water, DOC, and chloride fluxes increased by 7.1±1.3%, 8.0±1.3%, and 9.0±1.3%, respectively, within the reach, demonstrating that the adjacent wetlands are important sources of water and solutes to the stream. However, shallow groundwater Hg concentrations lower than in the surface water limited groundwater-surface water Hg exchange and no significant changes in Hg (filtered MeHg and THg) fluxes were observed within the reach despite the favorable hydraulic gradient. In August 2009, the lack of significant wetland-stream hydraulic gradient resulted in no net flux of water or solutes (MeHg, THg, DOC, or Cl) within the reach. The results are consistent with the wetland-Hg-source hypothesis and indicate that hydraulic and chemical gradient (direction and magnitude) interactions are fundamental controls on the supply of wetland Hg to the stream.

New York, South Carolina↗

USGS2016

Spatial and temporal variation in microcystins occurrence in wadeable streams in the southeastern USA

Despite historical observations of potential microcystin-producing cyanobacteria (including Leptolyngbya , Phormidium , Pseudoanabaena , and Anabaena species) in 74% of headwater streams in Alabama, Georgia, South Carolina, and North Carolina (USA) from 1993 to 2011, fluvial cyanotoxin occurrence has not been systematically assessed in the southeastern United States. To begin to address this data gap, a spatial reconnaissance of fluvial microcystin concentrations was conducted in 75 wadeable streams in the Piedmont region (southeastern USA) during June 2014. Microcystins were detected using enzyme-linked immunosorbent assay (limit = 0.10 µg/L) in 39% of the streams with mean, median, and maximum detected concentrations of 0.29 µg/L, 0.11 µg/L, and 3.2 µg/L, respectively. Significant (α = 0.05) correlations were observed between June 2014 microcystin concentrations and stream flow, total nitrogen to total phosphorus ratio, and water temperature; but each of these factors explained 38% or less of the variability in fluvial microcystins across the region. Temporal microcystin variability was assessed monthly through October 2014 in 5 of the streams where microcystins were observed in June and in 1 reference location; microcystins were repeatedly detected in all but the reference stream. Although microcystin concentrations in the present study did not exceed World Health Organization recreational guidance thresholds, their widespread occurrence demonstrates the need for further investigation of possible in-stream environmental health effects as well as potential impacts on downstream lakes and reservoirs. Environ Toxicol Chem 2016;9999:1–7. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US Government work and, as such, is in the public domain in the United States of America.

Alabama, Georgia, Maryland, North Carolina, South ↗

USGS2016

Pre/post-closure assessment of groundwater pharmaceutical fate in a wastewater‑facility-impacted stream reach

Pharmaceutical contamination of contiguous groundwater is a substantial concern in wastewater-impacted streams, due to ubiquity in effluent, high aqueous mobility, designed bioactivity, and to effluent-driven hydraulic gradients. Wastewater treatment facility (WWTF) closures are rare environmental remediation events; offering unique insights into contaminant persistence, long-term wastewater impacts, and ecosystem recovery processes. The USGS conducted a combined pre/post-closure groundwater assessment adjacent to an effluent-impacted reach of Fourmile Creek, Ankeny, Iowa, USA. Higher surface-water concentrations, consistent surface-water to groundwater concentration gradients, and sustained groundwater detections tens of meters from the stream bank demonstrated the importance of WWTF effluent as the source of groundwater pharmaceuticals as well as the persistence of these contaminants under effluent-driven, pre-closure conditions. The number of analytes (110 total) detected in surface water decreased from 69 prior to closure down to 8 in the first post-closure sampling event approximately 30 d later, with a corresponding 2 order of magnitude decrease in the cumulative concentration of detected analytes. Post-closure cumulative concentrations of detected analytes were approximately 5 times higher in proximal groundwater than in surface water. About 40% of the 21 contaminants detected in a downstream groundwater transect immediately before WWTF closure exhibited rapid attenuation with estimated half-lives on the order of a few days; however, a comparable number exhibited no consistent attenuation during the year-long post-closure assessment. The results demonstrate the potential for effluent-impacted shallow groundwater systems to accumulate pharmaceutical contaminants and serve as long-term residual sources, further increasing the risk of adverse ecological effects in groundwater and the near-stream ecosystem.

Iowa↗

USGS2016

Understanding the hydrologic impacts of wastewater treatment plant discharge to shallow groundwater: Before and after plant shutdown

Effluent-impacted surface water has the potential to transport not only water, but wastewater-derived contaminants to shallow groundwater systems. To better understand the effects of effluent discharge on in-stream and near-stream hydrologic conditions in wastewater-impacted systems, water-level changes were monitored in hyporheic-zone and shallow-groundwater piezometers in a reach of Fourmile Creek adjacent to and downstream of the Ankeny (Iowa, USA) wastewater treatment plant (WWTP). Water-level changes were monitored from approximately 1.5 months before to 0.5 months after WWTP closure. Diurnal patterns in WWTP discharge were closely mirrored in stream and shallow-groundwater levels immediately upstream and up to 3 km downstream of the outfall, indicating that such discharge was the primary control on water levels before shutdown. The hydrologic response to WWTP shutdown was immediately observed throughout the study reach, verifying the far-reaching hydraulic connectivity and associated contaminant transport risk. The movement of WWTP effluent into alluvial aquifers has implications for potential WWTP-derived contamination of shallow groundwater far removed from the WWTP outfall.

Iowa↗