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At least 1,459 records · Page 81Linked to original sources
USGS1997

Mass balance approach to selenium cycling through the San Joaquin Valley, sources to river to bay

Surface and ground waters of the Central Valley of California (e.g., rivers, dams, off-stream storage reservoirs, pumping facilities, irrigation and drinking water supply canals, agricultural drainage canals) are part of a hydrologic system that makes up a complex ecosystem extending from the riparian wetlands of the Sacramento and San Joaquin Rivers through the San Francisco Bay/Delta Estuary to the Pacific Ocean (Fig. 1). Water quality concerns center on elevated selenium (Se) and salt concentrations in irrigation drainage water discharged into the waterways of the relatively arid San Joaquin Valley (SJV), including the San Joaquin River (SJR). These waters are made unique by dissolved Se, weathered from marine sedimentary rocks of the Coast Ranges to the west, being ultimately concentrated to toxic levels in aquatic wildlife in the wetlands of the SJV/SJR trough (Figs. 1 and 2) (Presser and Ohlendorf, 1987; Presser, 1994). Scientific and environmental concerns focus on the bioreactive properties of Se and its partitioning among biota, water, and sediment, and on whether simple dilution models can be applied to an element that bioaccumulates. Because of state and federal commitments to provide water for irrigation, as well as drainage of irriga­ tion wastewater by the year 2000 drainage from over 180,000 ha of seleniferous, salinized farmland within the western SJV will create approximately 387 million cubic meters of potentially toxic drainage water annually (i.e., “problem water,” as defined by the San Joaquin Valley Drainage Program, 1990), thus lending urgency to an understanding of the biogeochemistry of Se in this environment.

California↗
USGS2019

Spatial and temporal variability of fish assemblages in acidified streams: Implications for long-term monitoring

Numerous studies have established strong linkages between acid deposition, soil and surface-water acidification, and toxicity to aquatic biota. Little is known however, about the effects of acidification on fish assemblages in headwater streams because they are highly variable, and pre-acidification data are often lacking. The primary purpose of this study was to describe spatial and interannual (temporal) variability of fish assemblages in headwater streams affected by acidification so that future recovery targets and monitoring strategies can be established. Fish communities and water chemistry were sampled at 48 headwater streams in the Western Adirondack Mountains of New York during the summers of 2014 to 2016 to characterize the present-day condition of water quality and local fish assemblages. Additionally, data from six Adirondack streams that were sampled annually from 2014-16 were combined with data from seven streams in the Catskill Mountain region sampled annually for three or more years for an analysis of temporal variability. Inorganic monomeric aluminum concentrations (Ali, the toxic form of Al) were less than 1.0 µmol L-1, between 1 and 2 µmol L-1, and greater than 2 µmol L-1 in 79%, 13%, and 8% of the 48 Adirondack streams. Richness, abundance, and biomass of fish assemblages were negatively related to Ali concentrations. In streams with Ali concentrations less than 1.0 µmol L-1, species richness, density, and biomass averaged 2.0 species, 444.2 fish/0.1 ha, and 1924.4 g/0.1 ha, respectively, and the density and biomass of Brook Trout populations averaged 280.8 fish/0.1 ha and 1384.0 g/0.1 ha. These values may provide a reasonable approximation of fish community condition prior to anthropogenic acidification and can be used as targets for assessing future recovery of acidified streams. A power analysis that considered 21 fish metrics indicated a strong negative relationship between interannual metric variability and statistical power for detecting change over time. Large differences were identified in the sample size necessary to achieve adequate power (0.8) depending on the metric utilized. In general, greater statistical power was obtained from metrics based on entire fish communities and from metrics standardized by reach length or sampling effort. Given the variability observed in our dataset, most metrics could detect a change of 30% with moderate effort, suggesting this may be an appropriate goal for future monitoring. Together, knowledge of biological recovery targets and the statistical power obtained from various fish metrics can be used to develop the most effective strategies for monitoring and assessing biological recovery in New York streams.

New York↗
USGS2020

Review of studies of composition, toxicology and human health impacts of wastewater from unconventional oil and gas development from shale

Unconventional oil and gas (UOG) extractions has produced large economic benefits. However, prudent management of UOG wastes necessitates a thorough understanding of the complex composition, fate, and potential impacts of wastewater releases. UOG production results in large volumes of wastewater. Despite limited re-use of the wastewater, the majority needs to be disposed of, usually by underground injection. The wastewater contains myriad organic, inorganic, and radioactive substances from hydraulic fracturing and production activities or from the (typically shale) formation. Many substances in this wastewater are either proprietary, or are known or potential toxicants. Limited toxicological studies of these mixtures suggest that some of the components are highly toxic. Thus, any releases of untreated wastewater may represent a threat to environmental integrity and human health.

Book chapter↗
USGS1996

Contaminants in the Gulf of Maine-What's here and should we worry?

The Gulf of Maine is a dynamic environment that has highly variable bottom type and localized depositional and transport processes. It is used and impacted by the people around it who hope to use the marine system for many purposes such as fishing, recreation, housing, sewage and dumped disposal, shipping, recreation, and preservation. In order to identify "pollution", which is defined as detrimental effects in the ecosystem that are attributable to human activity, the spatial and temporal distribution of contaminants in Gulf of Maine sediments are established using data that have been compiled into a Contaminated-Sediment Database for the Gulf of Maine. The potential for high contaminant levels in the sediments to induce toxic effects in the Gulf ecosystem is then assessed. In the Gulf of Maine, we have large urban centers that adversely affect the marine ecosystem well offshore through a variety of human activities. We are also in the fortunate position of still having many relatively pristine marine areas. It is unlikely that we will reach an endpoint of "zero toxic effects" in the ecosystem; however, much of the information needed to move closer to the shared goal of managing a sustainable ecosystem in the Gulf of Maine is currently available. Future success will rely on continued efforts to 1) identify rate-limiting physical and biological processes, 2) provide appropriate data synthesis and 3) involve the public.

Maine, Massachusetts, New Hampshire↗
USGS2020

The response of streams to changes in atmospheric deposition of sulfur and nitrogen in the Adirondack Mountains

Acidic deposition is the result of upwind sulfur (S) and nitrogen (N) emissions into the atmosphere from human activities. Environmental impacts from acidic deposition across forested landscapes include acidification of soil and drainage water, depletion of available soil nutrient bases, and impacts to and changes in forest and aquatic species composition and biodiversity. Acidic deposition can mobilize aluminum (Al) from soil-to-soil solution and subsequently to drainage water in forms that can be toxic to aquatic life. When exposed to decreasing levels of acidic deposition, which has been occurring in New York since the late 1970s, some soils and drainage waters have become gradually less acidic. Remaining questions relate to effects on stream resources, anticipated resource recovery under increasingly lower levels of deposition, and the levels of deposition (target loads, TLs) needed to reach a range of stream ecosystem recovery targets. Environmental scientists commonly estimate thresholds of air pollutant emissions and resulting atmospheric deposition at which adverse ecological effects are manifested. This analysis is often done using critical loads (CL) and/or TLs, using approaches that account for the spatial and temporal aspects of acidification and recovery. Exceedance represents the extent to which current levels of acidic deposition exceed the level expected to cause ecological harm. The research reported here is intended to help address S and N deposition TLs and ecosystem recovery of Adirondack streams, a resource that has been less thoroughly investigated than lakes. The overarching goal of this work is to highlight key considerations that will help inform decision-makers and ecosystem managers who are responsible for environmental policy in New York State and beyond. Salient aspects of stream TL modeling are discussed with an aim of informing not only scientists, but also policymakers, ecosystem managers, and nonscientists who are required to make decisions related to the effects of acidic deposition on natural ecosystems. Analyses reported herein quantify relations among chemical indicators and metrics of fish community health and biodiversity in streams of the Adirondack Park. This information is used to indicate levels of atmospheric deposition necessary to alleviate harmful effects on fish populations. Results of this investigation provide a framework that can be applied to better understand how modeled stream acid neutralizing capacity (ANC) values that are developed to support TL investigations can be adjusted to reflect high-flow ANC values that may be associated with toxic conditions. Since process models are often calibrated to a low-flow or average flow condition, the magnitude and spatial extent of TL exceedances increase substantially when episodic acidification is considered.

New York↗
USGS2020

Micrometer-scale characterization of solid mine waste aids in closure due diligence

Precious- and base-metal mining often occurs in deposits with high acid-generating potential, resulting in mine waste that contains metals in forms of varying bioavailability, and therefore toxicity. The solids that host these metals are often noncrystalline, nanometer to micrometer in size, or undetectable by readily available analytical techniques (e.g., X-ray diffraction). This analytical shortcoming can pose a challenge when attempting to characterize sources and natural attenuation of metals at a given site, which is a best practice to satisfy closure due diligence. Numerous case studies have shown that efforts to characterize mine waste at multiple scales, particularly the micrometer scale, often lead to a better understanding of metal distribution and potential contamination risks. This paper presents a case study that compares the use of both traditional and non-traditional techniques to identify and quantify metal hosts in sediments downstream of the abandoned mine waste piles at the Ely Copper Mine Superfund site in Vermont (USA). The contaminant present in the highest concentration in the sediments is copper, yet not all copper-bearing solids were detected with bulk X-ray diffraction (XRD). At the micrometer scale, a combination of synchrotron-based X-ray absorption spectroscopy (XAS) and an automated mineralogy (AM) system were used to identify the most abundant copper-bearing solids. Bulk XAS and AM also provided semi-quantitative abundances of these solids in the sediment. At the Ely Copper Mine, copper in stream sediments was found to be predominantly hosted in sulphide minerals downstream of a major mine waste pile, whereas upstream copper was predominantly hosted in secondary iron and manganese (oxyhydr)oxides. These copper-bearing hosts were consistent with the expected bioavailability of copper in the sediments based on laboratory toxicity tests with aquatic organisms. When the bulk of copper was present in sulphides, aquatic organisms experienced greater survival than when copper was mostly associated with secondary iron and manganese (oxyhydr)oxides. The information gained from probing the sediments at multiple scales can now be used to prioritize containment and remediation strategies. While synchrotron-based analytical techniques have proven to be invaluable in many studies of mine waste, access to these techniques is limited. In contrast, access to a scanning electron microscope that can perform AM is becoming more common, primarily for the application in mining design and mineral processing operations. More recently, the successful use of AM to characterize mine waste suggests that this technique can be equally as valuable for mine closure plans. The resolution of information obtained may go beyond what is required from a regulatory perspective, but given that the results have the potential to be more conclusive than many traditional techniques, this level of characterization may save time and money in the long run.

Vermont↗
USGS2024

Brodifacoum isomer formulations with potentially lower risk to non-target wildlife

Anticoagulant rodenticides (ARs) have a long history of successful use in controlling vertebrate pest and invasive species. Despite regulatory efforts to mitigate risk, non-target wildlife may be unintentionally exposed to ARs through various trophic pathways, and depending on dose, exposure can result in adverse effects and mortality. Second-generation ARs (SGARs) are mixtures of cis- and trans-diastereoisomers (each including two stereoisomers) that exhibit similar in vitro inhibitory potency for vitamin K epoxide reductase in rodent microsomal assay systems. Some diastereoisomers and hence some individual stereoisomers are preferentially metabolized in vivo, resulting in residue patterns in exposed target rodents that differ from the bait formulations. Use of less persistent but equally potent SGAR stereoisomers in baits results in lower tissue residues in target rodents, which in turn constitutes lower risk when consumed by non-target wildlife. The toxicity of two brodifacoum formulations with stereoisomers having markedly different elimination half-lives in rats (Formulation A containing the two least persistent stereoisomers, and Formulation B containing the most persistent stereoisomer) were tested in a 7-day dietary feeding trial with American kestrels. Based on previous kestrel studies using commercially available brodifacoum, Formulations A and B were each provided at three dietary concentrations (0.05, 0.1 and 0.5 µg/g diet, 4 kestrels/dose level) predicted to cause a range of toxicity. Compared to unexposed controls, all kestrels that ingested 0.5 µg/g diet of the longer-lived Formulation B exhibited extreme coagulopathy. In contrast, the 0.5 µg/g diet of the shorter-lived Formulation A yielded only a modest lengthening of clotting time in just 1 of the 4 exposed kestrels. These findings support the notion that SGAR baits enriched with less persistent stereoisomers may pose lower hazard and ultimately risk to non-target wildlife.

Conference Paper↗
USGS2022

Changes in stream chemistry in the east-central Adirondack region of New York State, 2010–2018

Decreased acidic deposition occurred through the 2010s, extending the long-term decrease begun in the early 1980s. The overall decline has resulted in rates of acidic deposition in the Adirondack region that are similar to those estimated for the early 1900s. This achievement increased attention on the issue of acidic deposition recovery and raised the question of how the low deposition levels of the 2010s were affecting the Adirondack region of New York State, where past acidic deposition effects were among the highest in the United States. This report presents stream resampling results of the East-Central Adirondack Stream Survey (ECASS), the Adirondack high-elevation stream sampling program, and the first five years of stream chemistry measurements in the Boreas River Long-Term Monitoring Watersheds. In addition, a regional comparison of stream chemistry between ECASS and the Western Adirondack Stream Survey (WASS) is presented. The primary objective of these stream resampling programs was to evaluate changes in stream chemistry during the 2010s to evaluate ongoing recovery of acidic deposition within the Adirondack region. Streams in the ECASS region (19,658 km 2 ) were sampled during spring snowmelt in 2011, 2017, and 2018; summer baseflow in 2010 and 2017; and late autumn in 2011 and 2017. ECASS stream sampling results for snowmelt in 2018 are also compared with WASS stream sampling results during snowmelt of the same year to provide a spatial assessment of stream chemistry for the entire Adirondack region. In addition, high-elevation streams were sampled in 2010-2011 and 2017 during spring snowmelt and summer baseflow, and three streams in the Boreas River watershed were sampled biweekly from 2014 through 2019. Streams were selected for sampling from the approximately 200 streams sampled originally in both the ECASS and WASS. The original ECASS and WASS streams were randomly selected from the populations of accessible streams within their respective regions. For the study reported here, subsets of streams were selected from the two original groups using a random stratified design based on the stream chemistry of the original ECASS and WASS. ECASS data are presented only for streams that were sampled in each of the seasonal surveys, which was 59, 48, and 61 streams for spring snowmelt, summer baseflow, and autumn surveys, respectively. WASS data are presented for 60 streams and high-elevation data are presented for 11 streams sampled during summer baseflow and 12 streams sampled during spring snowmelt. Overall, mean values of chemical measurements did not indicate large changes between 2010-2011 and 2017-2018 in the ECASS snowmelt, summer baseflow, or autumn surveys. Minimal acidification was observed in mean values measured in any of the surveys. Mean values of acid-neutralizing capacity (ANC) remained above 80 microequivalents per liter (µeq L -1 ), mean pH remained above 6.37, and inorganic monomeric aluminum (Al i ) remained below 1.0 micromoles per liter (µmol L -1 ), with the exception of the mean value of 1.2 µmol L -1 in the 2017 autumn survey. However, in the 2017 and 2018 snowmelt samplings 15% and 10% of the streams, respectively, had Al i concentrations above 1.0 µmol L 1 , the concentration above which is toxic to fish. Based on the estimated total length of headwater streams in the ECASS region of 11,494 km, the 10% of ECASS streams that experienced harmful Al i concentrations (Al i >1.0 µmol L -1 ) during the 2018 snowmelt survey equated to a total length of 1,091 km of headwater stream length in the region. During both summer baseflow and snowmelt sampling, high-elevation streams were less acidic in 2017 than in 2010-2011. However, in 2017 the mean Al i concentration during snowmelt was 2.6 µmol L -1 , a value that reflected low to moderate toxicity to brook trout. Concentrations of Al i in 9 out of the 12 streams were above 1.5 µmol L -1 , which exceeds the value which impairs fish communities. Greater dilution of calcium (Ca 2+ ) concentrations than sulfate (SO 4 2- ) concentrations during snowmelt was a contributing factor to the more acidic stream water measured during snowmelt than summer baseflow. Comparison of 2018 ECASS and WASS snowmelt chemistry under the current low levels of acidic deposition indicated that the spatial pattern of acidification effects on stream chemistry is largely driven by inherent Ca 2+ availability tied to spatial variations in geologic factors that control acid buffering more effectively in the ECASS region than the WASS region. The higher degree of acidification in the WASS region than the ECASS region is likely to extend into the future as a result of the relatively high dissolved organic carbon (DOC) concentrations in the WASS. Pronounced increasing trends in DOC and similarly pronounced decreasing trends in Ca 2+ and nitrate (NO 3 - ) were observed in the streams of all three Boreas River watersheds. These strong increasing DOC trends occurred in streams during a period with little or no indication of further chemical recovery from acidic deposition. The strong DOC trends in Durgin Brook and Balsam Brook, which are streams that are unlikely to have ever experienced more than minimal acidification, suggest the need for further investigation to expand our understanding of the mechanisms behind the increasing DOC trends.

New York↗
USGS1992

Water quality changes and their relation to fishery resources in the upper Mississippi River

Despite a long history of human manipulation, the most dramatic changes in the upper Mississippi River occurred in the 1930s with construction of a lock and dam system to facilitate the commercial transport of commodities. In 1988, barge traffic through the system ranged from 7,500 tows per year at Lock and Dam 26 (near Alton, Illinois) to 1, 118 at Lock and Dam 1 (in Minneapolis/St. Paul). The tow-teed dam system created a diversity of lentic habitats, but it also changed the stage and sediment transport characteristics of the river. The principal fishery-related water quality issues of this modified system concern the effects of sediments and toxic contaminants from nonpoint sources. Between 42 and 99% of the streams in the five states of the Mississippi River basin fail to fully support their designated uses because of pollution. primarily from nonpoint sources (e.g., 73% in Minnesota, 98% in Wisconsin, 75% in Illinois). Annual sediment inputs into the upper Mississippi River basin range from minimal in the upper reaches to about 210.000 kg/hectare in the lower reaches. This sediment results in significant losses of fishery habitat. Although bnly 5 to 9% of the total open water area of many pools had been lost by 1975, those losses were in highly productive side channel and backwater areas. Under existing conditions, a loss of an additional 22 to 49% of existing lentic habitats is predicted within 50 years. In addition, toxic contaminants transported along with fine sediments have become more available to stream biota. Although significant interagency efforts have been made to evaluate the impacts on biotic communities of the river. present data are inadequate to determine how changes in water quality affect the fisheries. This lack of data undermines our ability to judge the success of programs initiated to control pollution from point and nonpoint sources.

Book chapter↗
USGS1999

Estimation of environmental properties for inorganic compounds using LSER

The Great Lakes Science Center has devised values for inorganic species for use in the environmental property- predictive quantitative structure-activity relationships (QSAR) Linear Solvation Energy Relationship (LSER). Property estimation has been difficult for inorganic species. In this presentation aqueous solubility, bioconcentration and acute aquatic toxicity are estimated for inorganic compounds using existing LSER equations. The best estimations arise from the most accurate description of predominant solution species, many within an order of magnitude. The toxicities also depend on an estimation of the bioactive amount and configuration. A number of anion/cation combinations (salts) still resist accurate property estimation, and the reasons currently are not understood. These new variable values will greatly extend the application and utility of LSER for the estimation of environmental properties.

Conference Paper↗
USGS1995

Baseline risk assessment for aquatic life for the Buffalo River, New York, Area of Concern

The Great Lakes National Program Office of the U.S. Environmental Protection Agency initiated the Assessment and Remediation of Contaminated Sediments (ARCS) program to address concerns of environmental degradation at 43 Areas of Concern in the Great Lakes. In our first report (Passino-Reader et al. 1992), we developed a generic approach for baseline hazard evaluation of aquatic life in the Great Lakes Areas of Concern. In this report, we demonstrate the application of the generic approach to the Buffalo River (New York) Area of Concern. Using available historical data on residues in sediments, water, and biota, we evaluated exposure for 41 contaminants from the Buffalo River for eight taxa of fish and invertebrates representing the major trophic levels in the Buffalo River. By comparing exposure concentrations with reference toxicities, we calculated risk to the eight receptor organisms for typical and worst cases of exposure to the 41 contaminants. For mixtures of the contaminants present at the Buffalo River, primarily metals and polyaromatic hydrocarbons, we compared sediment concentrations with effects range-low (EL-R) values as reference values for toxicity of mixtures to estimate risk to aquatic biota.

Report↗
USGS1994

Waterfowl botulism--a brief summary

Botulism is a food poisoning caused by the ingestion of the toxin produced by the bacterium Clostridium botulinum of any of six strains, designated A through F. The disease, as it occurs in epidemic proportion in wild birds, is most commonly of the C type, although outbreaks caused by type E botulism have been observed on the Great Lakes. C. botulinum is a widely distributed anaerobic bacterium which is capable of existence for many years in spore form. Its vegetative cells grow and synthesize toxin, whenever and wherever the proper conditions exist in their environment. Outbreaks of botulism occur when aquatic birds consume this toxin which has been preformed in their food. Botulism is, therefore, an intoxication rather than an infection and is not a contagious disease. Botulism can be diagnosed conclusively only by demonstration of the toxin in the blood or serum of live affected birds, and a diagnostic laboratory should be contacted to confirm field diagnoses. A conclusive diagnosis cannot be reached by demonstrating the toxin or the organism in dead animals. The 'microenvironment concept' assumes that C. botulinum produces toxin in small, discrete, particulate food items which provide the requirements for growth of the bacteria independent of the surrounding wetland environment and which protect the toxin from dilution or inactivation. Optimum conditions for C. botulinum growth and toxin production include the absence of oxygen, a temperature of 76 deg. to 98 deg. F and suitable organic media, especially those composed of animal protein. Such conditions may be met in decaying invertebrate carcasses even though external conditions are unfavorable for toxin production. Vertebrate carcasses also may provide suitable conditions for the production of toxin, and maggots collected from duck carcasses during botulism outbreaks frequently contain extremely high levels of toxin. In determining the specific source of toxin and recommending control measures in the dynamic, complex, and diverse conditions of specific wetland ecosystem where botulism occurs, one's conclusions must necessarily become more speculative. Possibilities for reducing waterfowl losses due to botulism--Complete elimination of the causative organism, C. botulinum , from the wetland ecosystem is neither practical nor possible. Control methods may sometimes be profitably directed at prevention of toxin production, and the quantity of suitable media can be influenced. Rising water levels may drown terrestrial invertebrates, or flood vegetation thereby releasing nutrients which stimulate the increase in aquatic invertebrate populations to unstable levels which collapse. In other situations decreasing water levels may increase the numbers of invertebrate carcasses by increasing water temperatures or salinity which had been marginal for survival of previously thriving invertebrate populations or by stranding invertebrates on mud flats subject to periodic wind flooding. Therefore, a basic and important step in controlling botulism is stabilization of the wetland ecosystem in order to avoid the accumulation of decaying animal protein, especially during periods when temperatures are favorable for toxin production in these media. This can sometimes be accomplished by water level manipulation. If toxin production cannot be controlled by reducing the quantity of suitable media, another step is to prevent the ingestion of the toxic food items. Birds may be chased or lured from areas of toxin source or areas can be made less attractive by rapid and complete drainage, or draw down to a stable shoreline, where wind flooding does not occur. Removal of vertebrate carcasses, especially those of birds dying during the outbreak, reduces the availability of toxic maggots but carcass removal must be carried out frequently and diligently.Prevention of the effects of the toxin can be accomplished in some instances. Some degree of active immunity can be produced by injections of specific toxoi

Report↗
USGS2024

Predicted potential for aquatic exposure effects of per- and polyfluorinated alkyl substances (PFAS) in Pennsylvania’s statewide network of streams

Per- and polyfluoroalkyl substances (PFAS) are contaminants that can lead to adverse health effects in aquatic organisms, including reproductive toxicity and developmental abnormalities. To assess the ecological health risk of PFAS in Pennsylvania stream surface water, we conducted a comprehensive analysis that included both measured and predicted estimates. The potential combined exposure effects of 14 individual PFAS to aquatic biota were estimated using the sum of exposure-activity ratios ( Σ EARs) in 280 streams. Additionally, machine learning techniques were utilized to predict potential PFAS exposure effects in unmonitored stream reaches, considering factors such as land use, climate, and geology. Leveraging a tailored convolutional neural network (CNN), a validation accuracy of 78% was achieved, directly outperforming traditional methods that were also used, such as logistic regression and gradient boosting (accuracies of ~65%). Feature importance analysis highlighted key variables that contributed to the CNN’s predictive power. The most influential features highlighted the complex interplay of anthropogenic and environmental factors contributing to PFAS contamination in surface waters. Industrial and urban land cover, rainfall intensity, underlying geology, agricultural factors, and their interactions emerged as key determinants. These findings may help to inform biotic sampling strategies, water quality monitoring efforts, and policy decisions aimed to mitigate the ecological impacts of PFAS in surface waters.

Pennsylvania↗
USGS2001

Effect of 2,4-Dichlorophenoxyacetic acid herbicide Escherichia coli growth, chemical, composition, and cellular envelope

2,4-Dichlorophenoxyacetic acid (2,4-D) is a herbicide widely used in the world and mainly excreted by the renal route in exposed humans and animals. Herbicides can affect other nontarget organisms, such as Escherichia coli. We observed that a single exposure to 1 mM 2,4-D diminished growth and total protein content in all E. coli strains tested in vitro. In addition, successive exposures to 0.01 mM 2,4-D had a toxic effect decreasing growth up to early stationary phase. Uropathogenic E. coli adhere to epithelial cells mediated by fimbriae, adhesins, and hydrophobic properties. 2,4-D exposure of uropathogenic E. coli demonstrated altered hydrophobicity and fimbriation. Hydrophobicity index values obtained by partition in p-xylene/water were 300-420% higher in exposed cells than in control ones. Furthermore, values of hemagglutination titer, protein contents in fimbrial crude extract, and electron microscopy demonstrated a significant diminution of fimbriation in treated cells. Other envelope alterations could be detected, such as lipoperoxidation, evidenced by decreased polyunsaturated fatty acids and increased lipid degradation products (malonaldehyde), and motility diminution. These alterations decreased cell adherence to erythrocytes, indicating a diminished pathogenic capacity of the 2,4-D-exposed E. coli. ?? 2001 by John Wiley & Sons, Inc.

Environmental Toxicology↗
USGS2015

Organic contaminant transport and fate in the subsurface: evolution of knowledge and understanding

Toxic organic contaminants may enter the subsurface as slightly soluble and volatile nonaqueous phase liquids (NAPLs) or as dissolved solutes resulting in contaminant plumes emanating from the source zone. A large body of research published in Water Resources Research has been devoted to characterizing and understanding processes controlling the transport and fate of these organic contaminants and the effectiveness of natural attenuation, bioremediation, and other remedial technologies. These contributions include studies of NAPL flow, entrapment, and interphase mass transfer that have advanced from the analysis of simple systems with uniform properties and equilibrium contaminant phase partitioning to complex systems with pore-scale and macroscale heterogeneity and rate-limited interphase mass transfer. Understanding of the fate of dissolved organic plumes has advanced from when biodegradation was thought to require oxygen to recognition of the importance of anaerobic biodegradation, multiple redox zones, microbial enzyme kinetics, and mixing of organic contaminants and electron acceptors at plume fringes. Challenges remain in understanding the impacts of physical, chemical, biological, and hydrogeological heterogeneity, pore-scale interactions, and mixing on the fate of organic contaminants. Further effort is needed to successfully incorporate these processes into field-scale predictions of transport and fate. Regulations have greatly reduced the frequency of new point-source contamination problems; however, remediation at many legacy plumes remains challenging. A number of fields of current relevance are benefiting from research advances from point-source contaminant research. These include geologic carbon sequestration, nonpoint-source contamination, aquifer storage and recovery, the fate of contaminants from oil and gas development, and enhanced bioremediation.

Water Resources Research↗
USGS2010

Tools for assessing contaminated sediments in freshwater, estuarine, and marine ecosystems

Traditionally, concerns about the management of aquatic resources in aquatic ecosystems have focused primarily on water quality. As such, early water resource management efforts were often directed at assuring the potability of surface water or groundwater sources. Subsequently, the scope of these management initiatives expanded to include protection of instream (i.e., fish and aquatic life), agricultural, industrial, and recreational water uses. Although initiatives undertaken in the past 30 years have unquestionably improved water quality conditions, a growing body of evidence indicates that management efforts directed solely at the attainment of surface -water quality criteria may not provide an adequate basis for protecting the designated uses of aquatic ecosystems. In recent years, concerns about the health and vitality of aquatic ecosystems have begun to re -emerge in North America. One of the principal reasons for this is that many toxic and bioaccumulative chemicals, which are found in only trace amounts in water, can accumulate to elevated levels in sediments. Some of these pollutants, such as organochlorine (OC) pesticides and polychlorinated biphenyls (PCBs), were released into the environment long ago. The use of many of these substances has been banned in North America for 30 years or more; nevertheless, these chemicals continue to persist in the environment. Other contaminants enter our waters every day from industrial and municipal discharges, urban and agricultural runoff, and atmospheric deposition from remote sources. Owing to their physical and chemical properties, many of these substances tend to accumulate in sediments. In addition to providing sinks for many chemicals, sediments can also serve as potential sources of pollutants to the water column when conditions change in the receiving water system (for example during periods of anoxia, after severe storms).

Book chapter↗
USGS2017

A pesticide paradox: Fungicides indirectly increase fungal infections

There are many examples where the use of chemicals have had profound unintended consequences, such as fertilizers reducing crop yields (paradox of enrichment) and insecticides increasing insect pests (by reducing natural biocontrol). Recently, the application of agrochemicals, such as agricultural disinfectants and fungicides, has been explored as an approach to curb the pathogenic fungus, Batrachochytrium dendrobatidis ( Bd ), which is associated with worldwide amphibian declines. However, the long-term, net effects of early-life exposure to these chemicals on amphibian disease risk have not been thoroughly investigated. Using a combination of laboratory experiments and analysis of data from the literature, we explored the effects of fungicide exposure on Bd infections in two frog species. Extremely low concentrations of the fungicides azoxystrobin, chlorothalonil, and mancozeb were directly toxic to Bd in culture. However, estimated environmental concentrations of the fungicides did not reduce Bd on Cuban tree frog ( Osteopilus septentrionalis ) tadpoles exposed simultaneously to any of these fungicides and Bd , and fungicide exposure actually increased Bd -induced mortality. Additionally, exposure to any of these fungicides as tadpoles resulted in higher Bd abundance and greater Bd -induced mortality when challenged with Bd post-metamorphosis, an average of 71 d after their last fungicide exposure. Analysis of data from the literature revealed that previous exposure to the fungicide itraconazole, which is commonly used to clear Bd infections, made the critically endangered booroolong frog ( Litoria booroolongensis ) more susceptible to Bd . Finally, a field survey revealed that Bd prevalence was positively associated with concentrations of fungicides in ponds. Although fungicides show promise for controlling Bd , these results suggest that, if fungicides do not completely eliminate Bd or if Bd recolonizes, exposure to fungicides has the potential to do more harm than good. To ensure that fungicide applications have the intended consequence of curbing amphibian declines, researchers must identify which fungicides do not compromise the pathogen resistance mechanisms of amphibians.

Ecological Applications↗