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At least 757 records · Page 42Linked to original sources
USGS2007

Temporal changes in surface-water insecticide concentrations after the phaseout of diazinon and chlorpyrifos

The recent (late 2001) federally mandated phaseout of diazinon and chlorpyrifos insecticide use in outdoor urban settings has resulted in a rapid decline in concentrations of these insecticides in urban streams and rivers in the northeastern and midwestern United States. Assessment of temporal insecticide trends at 20 sites showed that significant step decreases in diazinon concentrations occurred at 90% of the sites after the phaseout, with concentrations generally decreasing by over 50% in summer samples. Chlorpyrifos concentrations showed significant step decreases in at least 1 season at 3 of the 4 sites with sufficient data for analysis. The decrease in diazinon concentrations in response to the phaseout resulted in a decline in the frequency of concentrations exceeding the acute invertebrate water-quality benchmark of 0.1 μg/L from 10% of pre-phaseout summer samples to fewer than 1% of post-phaseout summer samples. Although some studies have indicated an increase in concentrations of carbaryl in response to the organophosphorous phaseout, carbaryl concentrations only increased at 1 site after the phaseout. A full assessment of the effect of the phaseout of diazinon and chlorpyrifos on surface water will require data on other insecticides used to replace these compounds.

Environmental Science & Technology↗
USGS2007

Using biodynamic models to reconcile differences between laboratory toxicity tests and field biomonitoring with aquatic insects

Aquatic insects often dominate lotic ecosystems, yet these organisms are under-represented in trace metal toxicity databases. Furthermore, toxicity data for aquatic insects do not appear to reflect their actual sensitivities to metals in nature, because the concentrations required to elicit toxicity in the laboratory are considerably higher than those found to impact insect communities in the field. New approaches are therefore needed to better understand how and why insects are differentially susceptible to metal exposures. Biodynamic modeling is a powerful tool for understanding interspecific differences in trace metal bioaccumulation. Because bioaccumulation alone does not necessarily correlate with toxicity, we combined biokinetic parameters associated with dissolved cadmium exposures with studies of the subcellular compartmentalization of accumulated Cd. This combination of physiological traits allowed us to make predictions of susceptibility differences to dissolved Cd in three aquatic insect taxa: Ephemerella excrucians , Rhithrogena morrisoni , and Rhyacophila sp. We compared these predictions with long-term field monitoring data and toxicity tests with closely related taxa: Ephemerella infrequens , Rhithrogena hageni , and Rhyacophila brunea. Kinetic parameters allowed us to estimate steady-state concentrations, the time required to reach steady state, and the concentrations of Cd projected to be in potentially toxic compartments for different species. Species-specific physiological traits identified using biodynamic models provided a means for better understanding why toxicity assays with insects have failed to provide meaningful estimates for metal concentrations that would be expected to be protective in nature.

Environmental Science & Technology↗
USGS2007

Transient simulations of nitrogen load for a coastal aquifer and embayment, Cape Cod, MA

A time-varying, multispecies, modular, three-dimensional transport model (MT3DMS) was developed to simulate groundwater transport of nitrogen from increasing sources on land to the shore of Nauset Marsh, a coastal embayment of the Cape Cod National Seashore. Simulated time-dependent nitrogen loads at the coast can be used to correlate with current observed coastal eutrophic effects, to predict current and ultimate effects of development, and to predict loads resulting from source remediation. A time-varying nitrogen load, corrected for subsurface loss, was applied to the land subsurface in the transport model based on five land-use coverages documenting increasing development from 1951 to 1999. Simulated nitrogen loads to Nauset Marsh increased from 230 kg/yr before 1930 to 4390 kg/yr in 2001 to 7130 kg/yr in 2100, assuming future nitrogen sources constant at the 1999 land-use rate. The simulated nitrogen load per area of embayment was 5 times greater for Salt Pond, a eutrophic landward extension of Nauset Marsh, than for other Nauset Marsh areas. Sensitivity analysis indicated that load results were little affected by changes in vertical discretization and annual recharge but much affected by the nitrogen loss rate assumed for a kettle lake downgradient from a landfill.

Environmental Science & Technology↗
USGS2007

Persistent chlordane concentrations in long island sound sediment: Implications from chlordane, 210 Pb, and 137 Cs profiles

Concentrations of chlordane, a banned termiticide and pesticide, were examined in recently collected surficial sediment (10 sites) and sediment cores (4 sites) in Long Island Sound (LIS).The highest chlordane concentrations were observed in western LIS, near highly urbanized areas. Chlordane concentrations did not decrease significantly in the past decade when compared to the data collected in 1996, consistent with the observation of near-constant chlordane levels in blue mussel tissues collected during the same time period. Chlordane concentrations in many of the sites exceeded levels above which harmful effects on sediment-dwelling organisms are expected to frequently occur. Chlordane concentrations in two of the four sediment cores showed a peak below the sediment surface, suggesting reduced chlordane inputs in recent years. The lack of a chlordane concentration maximum below the sediment surface in the other two cores, coupled with the lack of a well-defined 137 Cs peak, indicated significant sediment mixing. Simulations of 137 Cs and 210 Pb profiles in sediment cores with a simple sediment-mixing model were used to constrain both the deposition rate and the bioturbation rate of the sediment. Simulations of the chlordane profiles indicated continued chlordane input to LIS long after chlordane was phased out in the U.S. Continued chlordane input and significant sediment mixing may have contributed to the persistent chlordane concentrations in surficial sediment, which poses long-term threats to benthic organisms in LIS.

New York↗
USGS2007

Incidence of the enterococcal surface protein ( esp ) gene in human and animal fecal sources

The occurrence of the enterococcal surface protein ( esp ) gene in the opportunistic pathogens Enterococcus faecalis and E. faecium is well-documented in clinical research. Recently, the esp gene has been proposed as a marker of human pollution in environmental waters; however, information on its relative incidence in various human and animal fecal sources is limited. We have determined the occurrence of the esp gene in enterococci from human ( n = 64) and animal ( n = 233) fecal samples by polymerase chain reaction using two primer sets: one presumably specific for E. faecium ( esp fm ) and the other for both E. faecalis and E. faecium ( esp fs/fm ). We believe that this research is the first to explore the use of esp fs/fm for the detection of human waste in natural environmental settings. The incidence in human sources was 93.1% esp fm and 100% esp fs/fm in raw sewage influent; 30% for both esp fm and esp fs/fm in septic waste; and 0% esp fm and 80% esp fs/fm in active pit toilets. The overall occurrence of the gene in animal feces was 7.7% ( esp fs/fm ) and 4.7% ( esp fm ); animal types with positive results included dogs (9/43, all esp fm ), gulls (10/34, esp fs/fm ; 2/34, esp fm ), mice (3/22, all esp fs/fm ), and songbirds (5/55, all esp fs/fm ). The esp gene was not detected in cat (0/34), deer (0/4), goose (0/18), or raccoon (0/23) feces. The inconsistent occurrence, especially in septic and pit toilet sewage, suggests a low statistical power of discrimination between animal and human sources, which means a large number of replicates should be collected. Both esp fm and esp fs/fm were common in raw sewage, but neither one efficiently differentiated between animal and other human sources.

Environmental Science & Technology↗
USGS2007

Nitrogen isotopes as indicators of NOx source contributions to atmospheric nitrate deposition across the midwestern and northeastern United States

Global inputs of NO x are dominated by fossil fuel combustion from both stationary and vehicular sources and far exceed natural NO x sources. However, elucidating NO x sources to any given location remains a difficult challenge, despite the need for this information to develop sound regulatory and mitigation strategies. We present results from a regional-scale study of nitrogen isotopes (δ 15 N) in wet nitrate deposition across 33 sites in the midwestern and northeastern U.S. We demonstrate that spatial variations in δ 15 N are strongly correlated with NO x emissions from surrounding stationary sources and additionally that δ 15 N is more strongly correlated with surrounding stationary source NO x emissions than pH, SO 4 2- , or NO 3 - concentrations. Although emission inventories indicate that vehicle emissions are the dominant NO x source in the eastern U.S., our results suggest that wet NO 3 - deposition at sites in this study is strongly associated with NO x emissions from stationary sources. This suggests that large areas of the landscape potentially receive atmospheric NO y deposition inputs in excess of what one would infer from existing monitoring data alone. Moreover, we determined that spatial patterns in δ 15 N values are a robust indicator of stationary NO x contributions to wet NO 3 - deposition and hence a valuable complement to existing tools for assessing relationships between NO 3 - deposition, regional emission inventories, and for evaluating progress toward NO x reduction goals.

Connecticut, Maine, Massachusetts, New Hampshire, ↗
USGS2007

Comparison of fate and transport of isoxaflutole to atrazine and metolachlor in 10 Iowa rivers

Isoxaflutole (IXF), a newer low application rate herbicide, was introduced for weed control in corn (Zea mays) to use as an alternative to widely applied herbicides such as atrazine. The transport of IXF in streamwater has not been well-studied. The fate and transport of IXF and two of its degradation products was studied in 10 Iowa rivers during 2004. IXF rapidly degrades to the herbicidally active diketonitrile (DKN), which degrades to a biologically inactive benzoic acid (BA) analogue. IXF was detected in only four, DKN in 56, and BA in 43 of 75 samples. The concentrations of DKN and BA were approximately 2 orders of magnitude less than those of the commonly detected triazine and acetamide herbicides and their degradation products. Concentrations of IXF, DKN, and BA were highest during the May through June postplanting period. The concentration ratio of BA/DKN was similar to the deethylatrazine/atrazine ratio with smaller ratios occurring during May and June. The relative temporal variation of DKN and BA was similar to that observed for atrazine and deethylatrazine. This study shows that low application rate herbicides can have similar temporal transport patterns in streamwater as compared to more widely applied herbicides but at lower concentrations.

Iowa↗
USGS2007

Human enteric viruses in groundwater from a confined bedrock aquifer

Confined aquifers are overlain by low-permeability aquitards that are commonly assumed to protect underlying aquifers from microbial contaminants. However, empirical data on microbial contamination beneath aquitards is limited. This study determined the occurrence of human pathogenic viruses in well water from a deep sandstone aquifer confined by a regionally extensive shale aquitard. Three public water-supply wells were each sampled 10 times over 15 months. Samples were analyzed by reverse transcription−polymerase chain reaction (RT-PCR) for several virus groups and by cell culture for infectious enteroviruses. Seven of 30 samples were positive by RT-PCR for enteroviruses; one of these was positive for infectious echovirus 18. The virus-positive samples were collected from two wells cased through the aquitard, indicating the viruses were present in the confined aquifer. Samples from the same wells showed atmospheric tritium, indicating water recharged within the past few decades. Hydrogeologic conditions support rapid porous media transport of viruses through the upper sandstone aquifer to the top of the aquitard 61 m below ground surface. Natural fractures in the shale aquitard are one possible virus transport pathway through the aquitard; however, windows, cross-connecting well bores, or imperfect grout seals along well casings also may be involved. Deep confined aquifers can be more vulnerable to contamination by human viruses than commonly believed.

Wisconsin↗
USGS2007

A gel probe equilibrium sampler for measuring arsenic porewater profiles and sorption gradients in sediments: II. Field application to Haiwee reservoir sediment

Arsenic (As) geochemistry and sorption behavior were measured in As- and iron (Fe)-rich sediments of Haiwee Reservoir by deploying undoped (clear) polyacrylamide gels and hydrous ferric oxide (HFO)-doped gels in a gel probe equilibrium sampler, which is a novel technique for directly measuring the effects of porewater composition on As adsorption to Fe oxides phases in situ. Arsenic is deposited at the sediment surface as As(V) and is reduced to As(III) in the upper layers of the sediment (0-8 cm), but the reduction of As(V) does not cause mobilization into the porewater. Dissolved As and Fe concentrations increased at depth in the sediment column driven by the reductive dissolution of amorphous Fe(III) oxyhydroxides and conversion to a mixed Fe(II, III) green rust-type phase. Adsorption of As and phosphorous (P) onto HFO-doped gels was inhibited at intermediate depths (10-20 cm), possibly due to dissolved organic or inorganic carbon, indicating that dissolved As concentrations were at least partially controlled by porewater composition rather than surface site availability. In sediments that had been recently exposed to air, the region of sorption inhibition was not observed, suggesting that prior exposure to air affected the extent of reductive dissolution, porewater chemistry, and As adsorption behavior. Arsenic adsorption onto the HFO-doped gels increased at depths >20 cm, and the extent of adsorption was most likely controlled by the competitive effects of dissolved phosphate. Sediment As adsorption capacity appeared to be controlled by changes in porewater composition and competitive effects at shallower depths, and by reductive dissolution and availability of sorption sites at greater burial depths. ?? 2008 American Chemical Society.

Environmental Science & Technology↗
USGS2007

Cadmium ecophysiology in seven stonefly (Plecoptera) species: Delineating sources and estimating susceptibility

A major challenge in ecotoxicology lies in generating data under experimental conditions that are relevant to understanding contaminant effects in nature. Biodynamic modeling combines species-specific physiological traits to make predictions of metal bioaccumulation that fare well when tested in the field. We generated biodynamic models for seven predatory stonefly (Plecoptera) species representing the families Perlidae (5) and Perlodidae (2). Each taxon was exposed to cadmium independently via diet and via solution. Species varied approximately 2.6 fold in predicted steady-state cadmium concentrations. Diet was the predominant source of accumulated cadmium in five of the seven species and averaged 53.2 ± 9.6% and 90.2 ± 3.7% of net Cd accumulation in perlids and perlodids, respectively. Differences in Cd bioaccumulation between the two families were largely driven by differences in dissolved accumulation rates, which were considerably slower in perlodids than in perlids. We further examined the subcellular compartmentalization of Cd accumulated from independent aqueous and dietary exposures. Predicted steady-state concentrations were modified to only consider Cd accumulated in metal-sensitive subcellular compartments. These values ranged 5.3 fold. We discuss this variability within a phylogenetic context and its implications for bioassessment.

Environmental Science & Technology↗
USGS2008

Evaluation of statistical treatments of left-censored environmental data using coincident uncensored data sets: I. Summary statistics

The main classes of statistical treatment of below-detection limit (left-censored) environmental data for the determination of basic statistics that have been used in the literature are substitution methods, maximum likelihood, regression on order statistics (ROS), and nonparametric techniques. These treatments, along with using all instrument-generated data (even those below detection), were evaluated by examining data sets in which the true values of the censored data were known. It was found that for data sets with less than 70% censored data, the best technique overall for determination of summary statistics was the nonparametric Kaplan-Meier technique. ROS and the two substitution methods of assigning one-half the detection limit value to censored data or assigning a random number between zero and the detection limit to censored data were adequate alternatives. The use of these two substitution methods, however, requires a thorough understanding of how the laboratory censored the data. The technique of employing all instrument-generated data - including numbers below the detection limit - was found to be less adequate than the above techniques. At high degrees of censoring (greater than 70% censored data), no technique provided good estimates of summary statistics. Maximum likelihood techniques were found to be far inferior to all other treatments except substituting zero or the detection limit value to censored data.

Environmental Science & Technology↗
USGS2007

Uptake, elimination, and relative distribution of perchlorate in various tissues of channel catfish

This study was undertaken to determine the kinetics of uptake and elimination of perchlorate in channel catfish, Ictalurus punctatus. Perchlorate - an oxidizer used in solid fuel rockets, fireworks, and illuminating munitions - has been shown to effect thyroid function, causing hormone disruption and potential perturbations of metabolic activities. For the uptake study, catfish were exposed to 100 mg/L sodium perchlorate for 12 h to 5 d in the laboratory. Perchlorate in tissues was analyzed using ion chromatography. The highest perchlorate concentrations were found in the head and fillet, indicating that these tissues are the most important tissues to analyze when determining perchlorate uptake into large fish. To calculate uptake and elimination rate constants for fillet, gills, G-I tract, liver, and head, fish were exposed to 100 ppm sodium perchlorate for 5 days, and allowed to depurate in clean water for up to 20 days. The animals rapidly eliminated the perchlorate accumulated showing the highest elimination in fillet (Ke = 1.67 day -1) and lowest elimination in liver (Ke = 0.79 day -1). ?? 2007 American Chemical Society.

Environmental Science & Technology↗
USGS2008

N-15 NMR study of the immobilization of 2,4- and 2,6-dinitrotoluene in aerobic compost

Large-scale aerobic windrow composting has been used to bioremediate washout lagoon soils contaminated with the explosives TNT (2,4,6-trinitrotoluene) and RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) at several sites within the United States. We previously used 15 N NMR to investigate the reduction and binding of T 15 NT in aerobic bench -scale reactors simulating the conditions of windrow composting. These studies have been extended to 2,4-dinitrotoluene (2,4DNT) and 2,6-dinitrotoluene (2,6DNT), which, as impurities in TNT, are usually present wherever soils have been contaminated with TNT. Liquid-state 15 N NMR analyses of laboratory reactions between 4-methyl-3-nitroaniline- 15 N , the major monoamine reduction product of 2,4DNT, and the Elliot soil humic acid, both in the presence and absence of horseradish peroxidase, indicated that the amine underwent covalent binding with quinone and other carbonyl groups in the soil humic acid to form both heterocyclic and non-heterocyclic condensation products. Liquid-state 15 N NMR analyses of the methanol extracts of 20 day aerobic bench-scale composts of 2,4-di- 15 N -nitrotoluene and 2,6-di- 15 N -nitrotoluene revealed the presence of nitrite and monoamine, but not diamine, reduction products, indicating the occurrence of both dioxygenase enzyme and reductive degradation pathways. Solid-state CP/MAS 15 N NMR analyses of the whole composts, however, suggested that reduction to monoamines followed by covalent binding of the amines to organic matter was the predominant pathway.

Environmental Science & Technology↗
USGS2008

Reproductive disruption in fish downstream from an estrogenic wastewater effluent

To assess the impact of an estrogenic wastewater treatment plant (WWTP) effluent on fish reproduction, white suckers ( Catostomus commersoni ) were collected from immediately upstream and downstream (effluent site) of the city of Boulder, CO, WWTP outfall. Gonadal intersex, altered sex ratios, reduced gonad size, disrupted ovarian and testicular histopathology, and vitellogenin induction consistent with exposure to estrogenic wastewater contaminants were identified in white suckers downstream from the WWTP outfall and not at the upstream site. The sex ratio was female-biased at the effluent site in both the fall of 2003 and the spring of 2004; the frequency of males at the effluent site (17–21%) was half that of the upstream site (36–46%). Intersex white suckers comprised 18–22% of the population at the effluent site. Intersex fish were not found at the upstream site. Chemical analyses determined that the WWTP effluent contained a complex mixture of endocrine-active chemicals, including 17β-estradiol (E 2 ) 17α-ethynylestradiol, alkylphenols, and bisphenol A resulting in an estimated total estrogen equivalence of up to 31 ng E 2 L −1 . These results indicate that the reproductive potential of native fishes may be compromised in wastewater-dominated streams.

Colorado↗
USGS2007

Pesticides in U.S. streams and groundwater

A 10­-year study by the U.S. Geological Survey’s (USGS’s) National Water-­Quality Assessment (NAWQA) Program provides a national-­scale view of pesticide occurrence in streams and groundwater. The 1992-2001 study builds upon a preliminary analysis from NAWQA’s first phase of studies during 1992-1996 (1, 2). Pesticide data available from various studies prior to 1992 did not allow national assessment because of limited and variable geographic coverage (usually focusing on individual states or regions), sparse and inconsistent inclusion of pesticides in use, and variable sampling designs (3-5). The expanded geographic coverage and improved data following 10 years of study (Figure 1) confirm and reinforce previously reported findings and enable more detailed analyses of each topic. This article summarizes selected findings from a comprehensive report (6), with a focus on the nature of pesticide occurrence and potential significance to human health and stream ecosystems. Information on study design and methods as well as additional analysis of geographic patterns and trends in relation to use and management practices are available in the full report (6).

Environmental Science & Technology↗
USGS2010

XANES evidence for rapid arsenic(III) oxidation at magnetite and ferrihydrite surfaces by dissolved O2 via Fe2+-mediated reactions

To reduce the adverse effects of arsenic on humans, various technologies are used to remove arsenic from groundwater, most relying on As adsorption on Fe-(oxyhydr)oxides and concomitant oxidation of As(III) by dissolved O 2 . This reaction can be catalyzed by microbial activity or by strongly oxidizing radical species known to form upon oxidation of Fe(II) by dissolved O 2 . Such catalyzed oxidation reactions have been invoked to explain the enhanced kinetics of As(III) oxidation in aerated water, in the presence of zerovalent iron or dissolved Fe(II). In the present study, we used arsenic K-edge X-ray absorption near edge structure (XANES) spectroscopy to investigate the role of Fe(II) in the oxidation of As(III) at the surface of magnetite and ferrihydrite under oxygenated conditions. Our results show rapid oxidation of As(III) to As(V) upon sorption onto magnetite under oxic conditions at neutral pH. Moreover, under similar oxic conditions, As(III) oxidized upon sorption onto ferrihydrite only after addition of Fe(II) aq within the investigated time frame of 24 h. These results confirm that Fe(II) is able to catalyze As(III) oxidation in the presence of dissolved O 2 and suggest that oxidation of As(III) upon sorption on magnetite under oxic conditions can be explained by an Fe 2+ -mediated Fenton-like reactions. Thus, the present study shows that magnetite might be an efficient alternative to the current use of oxidants and Fe(II) to remove As from aerated water. In addition, this study emphasizes that special care is needed to preserve arsenic oxidation state during laboratory sorption experiments as well as in collecting As-bearing samples from natural environments.

Environmental Science and Technology↗
USGS2010

Pharmaceutical formulation facilities as sources of opioids and other pharmaceuticals to wastewater treatment plant effluents

Facilities involved in the manufacture of pharmaceutical products are an under-investigated source of pharmaceuticals to the environment. Between 2004 and 2009, 35 to 38 effluent samples were collected from each of three wastewater treatment plants (WWTPs) in New York and analyzed for seven pharmaceuticals including opioids and muscle relaxants. Two WWTPs (NY2 and NY3) receive substantial flows (>20% of plant flow) from pharmaceutical formulation facilities (PFF) and one (NY1) receives no PFF flow. Samples of effluents from 23 WWTPs across the United States were analyzed once for these pharmaceuticals as part of a national survey. Maximum pharmaceutical effluent concentrations for the national survey and NY1 effluent samples were generally <1 microg/L. Four pharmaceuticals (methadone, oxycodone, butalbital, and metaxalone) in samples of NY3 effluent had median concentrations ranging from 3.4 to >400 microg/L. Maximum concentrations of oxycodone (1700 microg/L) and metaxalone (3800 microg/L) in samples from NY3 effluent exceeded 1000 microg/L. Three pharmaceuticals (butalbital, carisoprodol, and oxycodone) in samples of NY2 effluent had median concentrations ranging from 2 to 11 microg/L. These findings suggest that current manufacturing practices at these PFFs can result in pharmaceuticals concentrations from 10 to 1000 times higher than those typically found in WWTP effluents.

Environmental Science & Technology↗
USGS2010

Partition coefficients of organic contaminants with carbohydrates

In view of the current lack of reliable partition coefficients for organic compounds with carbohydrates ( K ch ), carefully measured values with cellulose and starch, the two major forms of carbohydrates, are provided for a wide range of compounds: short-chain chlorinated hydrocarbons, halogenated benzenes, alkyl benzenes, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, and organochlorine pesticides. To ensure the accuracy of the K ch data, solute concentrations in both water and carbohydrate phases are measured by direct solvent extraction of the samples. For a given compound, the observed partition coefficient with cellulose ( K cl ) is virtually the same as that with starch ( K st ). This finding expedites the evaluation of organic contamination with different forms of carbohydrates. The presently determined K ch values of 13 PAHs are substantially lower (by 3−66 times) than the literature data; the latter are suspect as they were obtained with (i) presumably impure carbohydrate samples or (ii) indirectly measured equilibrium solute concentrations in carbohydrate and water phases. Although the K ch values are generally considerably lower than the respective K ow (octanol−water) or K lipid (lipid−water), accurate K ch data are duly required to accurately estimate the contamination of carbohydrates by organic compounds because of the abundance of carbohydrates over lipids in crops and plants. To overcome the current lack of reliable K ch data for organic compounds, a close correlation of log K ch with log K ow has been established for predicting the unavailable K ch data for low-polarity compounds.

Environmental Science and Technology↗