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At least 505 records · Page 28Linked to original sources
USGS2025

Imidacloprid in United States rivers, 2013–2022: Persistent presence and emerging chronic hazard

Imidacloprid, a neonicotinoid insecticide, is used for agricultural and nonagricultural purposes and is toxic to nontarget organisms at low concentrations in aquatic ecosystems. A total of 12,547 water samples were collected from 2013 to 2022 from 77 rivers across the United States (U.S.) and were analyzed to evaluate detections and temporal trends in imidacloprid concentrations. Imidacloprid was detected in 44% of all samples, and the mean concentration, adjusted for nondetect samples, of 24.9 ng/L (median = 11.9 ng/L) was more than twice the chronic benchmark for freshwater invertebrates (10 ng/L). This potential hazard to aquatic life was persistent, with 44% of the sites having a median concentration exceeding the chronic benchmark. Half of the sites ( n = 38) had increasing trends, including large river sites along the Mississippi River. The mean increase was 10.6 ng/L over the past decade, while only six sites indicated decreasing trends. The estimated total loading of imidacloprid delivered to the Gulf of America from 2013 to 2022 was 129,489 kg (142.7 U.S. ton). The extensive presence of imidacloprid in U.S. waterways, the high percentage of sites with trends of increasing concentrations, and the prevalence of concentrations exceeding chronic benchmarks suggest widespread persistent risks to ecosystem health.

Environmental Science & Technology↗
USGS2002

Sorption of vapors of some organic liquids on soil humic acid and its relation to partitioning of organic compounds in soil organic matter

Vapor sorption of water, ethanol, benzene, hexane, carbon tetrachloride, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethylene, and 1,2-dibromoethane on (Sanhedron) soil humic acid has been determined at room temperature. Isotherms for all organic liquids are highly linear over a wide range of relative pressure, characteristic of the partitioning (dissolution) of the organic compounds in soil humic acid. Polar liquids exhibit markedly greater sorption capacities on soil humic acid than relatively nonpolar liquids, in keeping with the polar nature of the soil humic acid as a partition medium. The limiting sorption (partition) capacities of relatively non-polar liquids are remarkably similar when expressed in terms of volumes per unit weight of soil humic acid. The soil humic acid is found to be about half as effective as soil organic matter in sorption of relatively nonpolar organic compounds. The nearly constant limiting sorption capacity for nonpolar organic liquids with soil humic acid on a volume-to-weight basis and its efficiency in sorption relative to soil organic matter provide a basis for predicting the approximate sorption (partition) coefficients of similar compounds in uptake by soil in aqueous systems.

Environmental Science & Technology↗
USGS2012

Geogenic sources of benzene in aquifers used for public supply, California

Statistical evaluation of two large statewide data sets from the California State Water Board's Groundwater Ambient Monitoring and Assessment Program (1973 wells) and the California Department of Public Health (12417 wells) reveals that benzene occurs infrequently (1.7%) and at generally low concentrations (median detected concentration of 0.024 &mu;g/L) in groundwater used for public supply in California. When detected, benzene is more often related to geogenic (45% of detections) than anthropogenic sources (27% of detections). Similar relations are evident for the sum of 17 hydrocarbons analyzed. Benzene occurs most frequently and at the highest concentrations in old, brackish, and reducing groundwater; the detection frequency was 13.0% in groundwater with tritium <1 pCi/L, specific conductance >1600 &mu;S/cm, and anoxic conditions. This groundwater is typically deep (>180 m). Benzene occurs somewhat less frequently in recent, shallow, and reducing groundwater; the detection frequency was 2.6% in groundwater with tritium ≥1 pCi/L, depth <30 m, and anoxic conditions. Evidence for geogenic sources of benzene include: higher concentrations and detection frequencies with increasing well depth, groundwater age, and proximity to oil and gas fields; and higher salinity and lower chloride/iodide ratios in old groundwater with detections of benzene, consistent with interactions with oil-field brines.

California↗
USGS2026

Rare earth element potential in coal and coal ash in the U.S. Gulf Coast

United States heavy reliance on imports of critical minerals (CMs), including rare earth elements (REEs), underscores the importance of development of domestic sources. The study objective was to quantify CM and REE concentrations in coal and coal ash in the US Gulf Coast region. CM and REE concentrations were measured for 118 samples from outcrops and 14 mines in the Gulf Coast. Results show that total REE + Yttrium (REY) concentrations (dry coal basis) are comparable to those of the upper continental crust (UCC) with localized hot spots, such as the Texas Gibbons Creek mine (REY ≤ ~ 2860 ppm). When normalized to UCC REY concentration (169 ppm, dry coal basis), REY to UCC ratios for Gulf Coast coal samples range from 0.1 to 17 (median ratio 0.6). REE extractability from lignites is high (median: 63%–93%) using environmentally benign weak acid. In addition to raw coal, coal ash from power plants could also serve as an REE source with a median ratio of REY in ash relative to coal of 4; however, extractability from coal ash is generally much lower (≤ 5% using the same weak acid as in coal). The median basket price for extracted REY as oxides from coal, assuming 70% extractability, is $3.2 per tonne of coal and $186 billion based on 58 billion metric tonnes of dry coal in the Gulf Coast. REEs important for magnets (Pr + Nd + Tb + Dy) account for ~ 80% of the total value. The corresponding median basket price for extracted REY as oxides from coal ash, assuming ~ 30% extractability, is ~$4.4 per tonne of ash and $1.2 billion based on 258 million tonnes of ash. REE production from coal would likely require co-products, such as activated carbon or humic acids, to attain economic viability. Production of REEs from coal ash could offset remediation costs related to potential water contamination. This reconnaissance study shows the potential for REE production from coal and coal ash in the Gulf Coast; however, carbon coproducts and/or societal benefits would likely be required for socioeconomic viability.

Alabama, Florida, Louisiana, Mississippi, Texas↗
USGS2011

Effects of the antimicrobial sulfamethoxazole on groundwater bacterial enrichment

The effects of “trace” (environmentally relevant) concentrations of the antimicrobial agent sulfamethoxazole (SMX) on the growth, nitrate reduction activity, and bacterial composition of an enrichment culture prepared with groundwater from a pristine zone of a sandy drinking-water aquifer on Cape Cod, MA, were assessed by laboratory incubations. When the enrichments were grown under heterotrophic denitrifying conditions and exposed to SMX, noticeable differences from the control (no SMX) were observed. Exposure to SMX in concentrations as low as 0.005 μM delayed the initiation of cell growth by up to 1 day and decreased nitrate reduction potential (total amount of nitrate reduced after 19 days) by 47% ( p = 0.02). Exposure to 1 μM SMX, a concentration below those prescribed for clinical applications but higher than concentrations typically detected in aqueous environments, resulted in additional inhibitions: reduced growth rates ( p = 5 × 10 −6 ), lower nitrate reduction rate potentials ( p = 0.01), and decreased overall representation of 16S rRNA gene sequences belonging to the genus Pseudomonas . The reduced abundance of Pseudomonas sequences in the libraries was replaced by sequences representing the genus Variovorax . Results of these growth and nitrate reduction experiments collectively suggest that subtherapeutic concentrations of SMX altered the composition of the enriched nitrate-reducing microcosms and inhibited nitrate reduction capabilities.

Environmental Science & Technology↗
USGS1999

Using imaging spectroscopy to map acidic mine waste

The process of pyrite oxidation at the surface of mine waste may produce acidic water that is gradually neutralized as it drains away from the waste, depositing different Fe-bearing secondary minerals in roughly concentric zones that emanate from mine-waste piles. These Fe-bearing minerals are indicators of the geochemical conditions under which they form. Airborne and orbital imaging spectrometers can be used to map these mineral zones because each of these Fe-bearing secondary minerals is spectrally unique. In this way, imaging spectroscopy can be used to rapidly screen entire mining districts for potential sources of surface acid drainage and to detect acid producing minerals in mine waste or unmined rock outcrops. Spectral data from the AVIRIS instrument were used to evaluate mine waste at the California Gulch Superfund Site near Leadville, CO. Laboratory leach tests of surface samples show that leachate pH is most acidic and metals most mobile in samples from the inner jarosite zone and that leachate pH is near-neutral and metals least mobile in samples from the outer goethite zone.

Environmental Science & Technology↗
USGS1996

Acetochlor in the hydrologic system in the midwestern United States, 1994

The herbicide acetochlor [2-chloro- N -(ethoxymethyl)- N -(2-ethyl-6-methylphenyl)acetamide] was given conditional registration in the United States by the U.S. Environmental Protection Agency in March 1994. This registration provided a rare opportunity to investigate the occurrence of a pesticide during its first season of extensive use in the midwestern United States. Water samples collected and analyzed by the U.S. Geological Survey during 1994 documented the distribution of acetochlor in the hydrologic system; it was detected in 29% of the rain samples from four sites in Iowa, 17% of the stream samples from 51 sites across nine states, and 0% of the groundwater samples from 38 wells across eight states. Acetochlor exhibited concentration increases in rain and streams following its application to corn in the midwestern United States, with 75% of the rainwater and 35% of the stream samples having acetochlor detected during this time period. Acetochlor concentrations in rain decreased as the growing season progressed. Based on the limited data collected for this study, it is anticipated that acetochlor concentrations will have a seasonal pattern in rain and streams similar to those of other acetanilide herbicides examined. Possible explanations for the absence of acetochlor in groundwater for this study include the rapid degradation of acetochlor in the soil zone, insufficient time for this first extensive use of acetochlor to have reached the aquifers sampled, and the possible lack of acetochlor use in the recharge areas for the wells examined.

Environmental Science & Technology↗
USGS1998

Butyltin residues in southern sea otters (Enhydra lutris nereis) found dead along California coastal waters

Tributyltin (TBT) and its degradation products, mono- (MBT) and dibutyltin (DBT), were determined in liver, kidney, and brain tissues of adult southern sea otters (Enhydra lutris nereis) found dead along the coast of California during 1992a??1996. Hepatic concentrations of butyltin compounds (BTs = MBT + DBT + TBT) ranged from 40 to 9200 ng/g wet wt, which varied depending on the sampling location and gender. Concentrations of BTs in sea otters were comparable to those reported in stranded bottlenose dolphins from the U.S. Atlantic Coast during 1989a??1994. Greater accumulation of butyltins in sea otters was explained by their bottom-feeding habit and the diet that consists exclusively of invertebrates such as mollusks and gastropods. Livers of female sea otters contained approximately 2-fold greater concentrations of BTs than did those of males. The composition of butyltin compounds in sea otter tissues was predominated by TBT in most cases and suggestive of recent exposure. Large harbors such as Monterey Harbor that handle ships legally painted with TBT-containing antifouling paints continued to experience ecotoxicologically significant butyltin contamination. Sea otters, which were affected by infectious diseases, contained greater concentrations of BTs in their tissues than those that died from trauma and other unknown causes.

Californnia↗
USGS2013

Increases in dissolved organic carbon accelerate loss of toxic Al in Adirondack lakes recovering from acidification

Increasing pH and decreasing Al in surface waters recovering from acidification have been accompanied by increasing concentrations of dissolved organic carbon (DOC) and associated organic acids that partially offset pH increases and complicate assessments of recovery from acidification. To better understand the processes of recovery, monthly chemistry from 42 lakes in the Adirondack region, NY, collected from 1994 to 2011, were used to (1) evaluate long-term changes in DOC and associated strongly acidic organic acids and (2) use the base-cation surplus (BCS) as a chemical index to assess the effects of increasing DOC concentrations on the Al chemistry of these lakes. Over the study period, the BCS increased (p < 0.01) and concentrations of toxic inorganic monomeric Al (IMAl) decreased (p < 0.01). The decreases in IMAl were greater than expected from the increases in the BCS. Higher DOC concentrations that increased organic complexation of Al resulted in a decrease in the IMAl fraction of total monomeric Al from 57% in 1994 to 23% in 2011. Increasing DOC concentrations have accelerated recovery in terms of decreasing toxic Al beyond that directly accomplished by reducing atmospheric deposition of strong mineral acids.

Environmental Science & Technology↗
USGS2003

Nonylphenol ethoxylates and other additives in aircraft deicers, antiicers, and waters receiving airport runoff

Samples of nine different formulations of aircraft deicer and antiicer fluids (ADAF) were screened for the presence of selected surfactants. Nonylphenol ethoxylates (NPnEO) were identified in three ADAF formulations, octylphenol ethoxylates were identified in two formulations, and six formulations contained alcohol ethoxylates. A preliminary field study was conducted at General Mitchell International Airport, Milwaukee, WI, to quantify NPnEO (n = 1-15) and one of its byproducts, nonylphenol (NP), in airport runoff. Samples were collected from two airport outfalls, from the receiving stream, and from an upstream reference site during intensive ADAF application events. NPnEO was measured at concentrations up to 1190microg/L in airport outfall samples, up to 77 ug/L in samples from the receiving stream and less than 5.0 microg/L from the upstream reference. Concentrations of glycol and other ADAF-related constituents, including NPnEO, were reduced by approximately 1 order of magnitude between the outfall sites and the receiving stream site; however, concentrations of NP in the receiving stream remained similar to those from the outfalls (< 0.04 microg/L at the upstream reference, 0.98 and 7.67 microg/L at outfalls, and 3.89 microg/L in the receiving stream). The field data suggest that NP is generated through degradation of NPnEO from airport runoff.

Wisconsin↗
USGS2021

Exposure and transport of alkaloids and phytoestrogens from soybeans to agricultural soils and streams in the Midwestern United States

Phytotoxins are naturally produced toxins with potencies similar/higher than many anthropogenic micropollutants. Nevertheless, little is known regarding their environmental fate and off-field transport to streams. To fill this research gap, a network of six basins in the Midwestern United States with substantial soybean production was selected for the study. Stream water ( n = 110), soybean plant tissues ( n = 8), and soil samples ( n = 16) were analyzed for 12 phytotoxins (5 alkaloids and 7 phytoestrogens) and 2 widely used herbicides (atrazine and metolachlor). Overall, at least 1 phytotoxin was detected in 82% of the samples, with as many as 11 phytotoxins detected in a single sample (median = 5), with a concentration range from below detection to 37 and 68 ng/L for alkaloids and phytoestrogens, respectively. In contrast, the herbicides were ubiquitously detected at substantially higher concentrations (atrazine: 99% and metolachlor: 83%; the concentrations range from below detection to 150 and 410 ng/L, respectively). There was an apparent seasonal pattern for phytotoxins, where occurrence prior to and during harvest season (September to November) and during the snow melt season (March) was higher than that in December–January. Runoff events increased phytotoxin and herbicide concentrations compared to those in base-flow conditions. Phytotoxin plant concentrations were orders of magnitude higher compared to those measured in soil and streams. These results demonstrate the potential exposure of aquatic and terrestrial organisms to soybean-derived phytotoxins.

Illinois, Indiana, Iowa, Minnesota, Missouri, Sout↗
USGS1996

Hydrologic and microbiological factors affecting persistence and migration of petroleum hydrocarbons spilled in a continuous-permafrost region

Fuel spills, totaling about 1300 m3, occurred between 1976 and 1978 adjacent to Imikpuk Lake, a drinking water source near Barrow, AK. Substantial contamination of soils and groundwater near the lake persists. We examined the magnitude and direction of groundwater flux and the microbial activity at this site to understand the persistence of contamination and its effect on the lake. We found that groundwater flux is small due to shallow permafrost, which restricts the cross-sectional area available for flow, and to the short annual thaw season (ca. 90 days). The small flux and limited depth also constrain contaminant transport and dispersion, resulting in persistent, shallow contamination. The numbers of hydrocarbon-oxidizing microorganisms and their laboratory mineralization potentials for benzene (at 10 ??C) were higher in samples from contaminated areas than in reference samples. Benzene mineralization potentials in groundwater samples were comparable to more temperate systems (0.1-0.5 mg of benzene mineralized L-1 day-1) and were stimulated by nutrient additions. Field measurements of dissolved oxygen, nitrate, ferrous iron, and sulfide in groundwater provided evidence that biodegradation of petroleum hydrocarbons is occurring in situ. Despite evidence of an active microbial population, microbial processes, like contaminant transport, are likely limited at this site by the short annual thaw season.

Environmental Science & Technology↗
USGS2013

A review of selected inorganic surface water quality-monitoring practices: are we really measuring what we think, and if so, are we doing it right?

Successful environmental/water quality-monitoring programs usually require a balance between analytical capabilities, the collection and preservation of representative samples, and available financial/personnel resources. Due to current economic conditions, monitoring programs are under increasing pressure to do more with less. Hence, a review of current sampling and analytical methodologies, and some of the underlying assumptions that form the bases for these programs seems appropriate, to see if they are achieving their intended objectives within acceptable error limits and/or measurement uncertainty, in a cost-effective manner. That evaluation appears to indicate that several common sampling/processing/analytical procedures (e.g., dip (point) samples/measurements, nitrogen determinations, total recoverable analytical procedures) are generating biased or nonrepresentative data, and that some of the underlying assumptions relative to current programs, such as calendar-based sampling and stationarity are no longer defensible. The extensive use of statistical models as well as surrogates (e.g., turbidity) also needs to be re-examined because the hydrologic interrelationships that support their use tend to be dynamic rather than static. As a result, a number of monitoring programs may need redesigning, some sampling and analytical procedures may need to be updated, and model/surrogate interrelationships may require recalibration.

Environmental Science & Technology↗
USGS2021

Assessing the impact of drought on arsenic exposure from private domestic wells in the conterminous United States

This study assesses the potential impact of drought on arsenic exposure from private domestic wells by using a previously developed statistical model that predicts the probability of elevated arsenic concentrations (>10 μg per liter) in water from domestic wells located in the conterminous United States (CONUS). The application of the model to simulate drought conditions used systematically reduced precipitation and recharge values. The drought conditions resulted in higher probabilities of elevated arsenic throughout most of the CONUS. While the increase in the probability of elevated arsenic was generally less than 10% at any one location, when considered over the entire CONUS, the increase has considerable public health implications. The population exposed to elevated arsenic from domestic wells was estimated to increase from approximately 2.7 million to 4.1 million people during drought. The model was also run using total annual precipitation and groundwater recharge values from the year 2012 when drought existed over a large extent of the CONUS. This simulation provided a method for comparing the duration of drought to changes in the predicted probability of high arsenic in domestic wells. These results suggest that the probability of exposure to arsenic concentrations greater than 10 μg per liter increases with increasing duration of drought. These findings indicate that drought has a potentially adverse impact on the arsenic hazard from domestic wells throughout the CONUS.

Conterminous United States↗
USGS2010

Influence of coal-tar sealcoat and other carbonaceous materials on polycyclic aromatic hydrocarbon loading in an urban watershed

Carbonaceous material (CM) particles are the principal vectors transporting polycyclic aromatic hydrocarbons (PAHs) into urban waters via runoff; however, characteristics of CM particles in urban watersheds and their relative contributions to PAH contamination remain unclear. Our objectives were to identify the sources and distribution of CM particles in an urban watershed and to determine the types of CMs that were the dominant sources of PAHs in the lake and stream sediments. Samples of soils, parking lot and street dust, and streambed and lake sediment were collected from the Lake Como watershed in Fort Worth, Texas. Characteristics of CM particles determined by organic petrography and a significant correlation between PAH concentrations and organic carbon in coal tar, asphalt, and soot indicate that these three CM particle types are the major sources and carriers of PAHs in the watershed. Estimates of the distribution of PAHs in CM particles indicate that coal-tar pitch, usedinsomepavementsealcoats, isadominant source of PAHs in the watershed, and contributes as much as 99% of the PAHs in sealed parking lot dust, 92% in unsealed parking lot dust, 88% in commercial area soil, 71% in streambed sediment, and 84% in surficial lake sediment. ?? 2010 American Chemical Society.

Environmental Science & Technology↗
USGS2006

Modeling the transport and inactivation of E. coli and enterococci in the near-shore region of Lake Michigan

To investigate the transport and fate of fecal pollution at Great Lakes beaches and the health risks associated with swimming, the near-shore waters of Lake Michigan and two tributaries discharging into it were examined for bacterial indicators of human fecal pollution. The enterococcus human fecal pollution marker, which targets a putative virulence factor the enterococcal surface protein (esp) in Enterococcus faecium , was detected in 2/28 samples (7%) in the tributaries draining into Lake Michigan and in 6/30 samples (20%) in Lake Michigan beaches. This was indicative of human fecal pollution being transported in the tributaries and occurrence at Lake Michigan beaches. To understand the relative importance of different processes influencing pollution transport and inactivation, a finite-element model of surf-zone hydrodynamics (coupled with models for temperature, E. coli and enterococci) was used. Enterococci appear to survive longer than E. coli , which was described using an overall first-order inactivation coefficient in the range 0.5&minus;2.0 per day. Our analysis suggests that the majority of fecal indicator bacteria variation can be explained based on loadings from the tributaries. Sunlight is a major contributor to inactivation in the surf-zone and the formulation based on sunlight, temperature and sedimentation is preferred over the first-order inactivation formulation.

Environmental Science & Technology↗
USGS2009

Investigation of river eutrophication as part of a low dissolved oxygen total maximum daily load implementation

In the United States, environmentally impaired rivers are subject to regulation under total maximum daily load (TMDL) regulations that specify watershed wide water quality standards. In California, the setting of TMDL standards is accompanied by the development of scientific and management plans directed at achieving specific water quality objectives. The San Joaquin River (SJR) in the Central Valley of California now has a TMDL for dissolved oxygen (DO). Low DO conditions in the SJR are caused in part by excessive phytoplankton growth (eutrophication) in the shallow, upstream portion of the river that create oxygen demand in the deeper estuary. This paper reports on scientific studies that were conducted to develop a mass balance on nutrients and phytoplankton in the SJR. A mass balance model was developed using WARMF, a model specifically designed for use in TMDL management applications. It was demonstrated that phytoplankton biomass accumulates rapidly in a 88 km reach where plankton from small, slow moving tributaries are diluted and combined with fresh nutrient inputs in faster moving water. The SJR-WARMF model was demonstrated to accurately predict phytoplankton growth in the SJR. Model results suggest that modest reductions in nutrients alone will not limit algal biomass accumulation, but that combined strategies of nutrient reduction and algal control in tributaries may have benefit. The SJR-WARMF model provides stakeholders a practical, scientific tool for setting remediation priorities on a watershed scale.

Water Science and Technology↗
USGS2018

Real-time nowcasting of microbiological water quality at recreational beaches: A wavelet and artificial neural network-based hybrid modeling approach

The number of beach closings caused by bacterial contamination has continued to rise in recent years, putting beachgoers at risk of exposure to contaminated water. Current approaches predict levels of indicator bacteria using regression models containing a number of explanatory variables. Data-based modeling approaches can supplement routine monitoring data and provide highly accurate short-term forecasts of beach water quality. In this paper, we apply the nonlinear autoregressive network with exogenous inputs (NARX) method with explanatory variables to predict Escherichia coli concentrations at four Lake Michigan beach sites. We also apply the nonlinear input–output network (NIO) and nonlinear autoregressive neural network (NAR) methods in addition to a hybrid wavelet-NAR (WA-NAR) model and demonstrate their application. All models were tested using 3 months of observed data. Results revealed that the NARX models provided the best performance and that the WA-NAR model, which requires no explanatory variables, outperformed the NIO and NAR models; therefore, the WA-NAR model is suitable for application to data scarce regions. The models proposed in this paper were evaluated using multiple performance metrics, including sensitivity and specificity measures, and produced results comparable or superior to those of previous mechanistic and statistical models developed for the same beach sites. The relatively high R 2 values between data and the NARX models ( R 2 values of ∼0.8 for the beach sites and ∼0.9 for the river site) indicate that the new class of models shows promise for beach management.

Environmental Science & Technology↗