Filters: Tags: contaminants (X)
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I conduct research focused on understanding the role of microorganisms on both contaminated and pristine ecosystems. I carry out this work using a polyphasic approach that combines microbiology, molecular biology, and biogeochemistry to understand microbial processes. My work specifically aims to (1) assess the impact of microorganisms on the fate of organic and inorganic contaminants; (2) to investigate the microbial role in metal cycling, e.g., iron, uranium, and manganese cycling; (3) evaluate the potential of microbial populations to contribute to energy resources, either through coal bed methane production or mitigating contaminants due to nuclear energy production or unconventional oil and gas production;...
Categories: Project;
Tags: Biogeochemistry,
Contaminants,
Ecology,
Metals,
Microbiology (Activity and Transport)
My research is concerned broadly with the use of stable isotopes, primarily hydrogen, carbon and oxygen, to examine the dynamics of hydrological systems and associated geochemical problems. I perform studies in the identification and quantification of ground-water recharge, discharge, surface-water/ground-water interaction, redox processes in contaminated aquifers, as well as source identification of stray methane gas in drinking water wells. I develop new sample- preparation techniques in the laboratory including inlet systems for continuous- flow isotope- ratio analytical techniques , such as EA, TC/EA, GPI, Gasbench, GCC, TC/GCC, and TIC/TOC and publish Sandard Operating Procedures in the U.S. Geological Survey...
Evaluate the hydrologic and geochemical processes that control nitrate fluxes in agricultural settings. Important questions remain about the overall regional and global importance of groundwater nitrogen fluxes, denitrification (microbial reduction of NO 3 − to N 2), and the sources of electron donors contributing to this microbial reaction. Studies are needed that apply robust methods for measuring nitrogen fluxes and denitrification among multiple sites to evaluate important factors affecting N fluxes. These results, in combination with novel methods for efficient estimation of fluxes in groundwater, facilitate estimates of N fluxes in across large regions such as the Corn Belt. Quantify the effects of complex...
Categories: Project;
Tags: Contaminants,
Groundwater Flow and Transport,
Groundwater-Surface Water Interactions,
Nitrogen Cycling,
Nutrients
Robin Stewart's research is focused on identifying and understanding processes influencing the fate and bioavailability of selenium and mercury in food webs across a range of aquatic environments including estuaries, rivers, lakes and reservoirs.
Categories: Project;
Tags: Bioaccumulation,
Bioavailability,
Biogeochemistry,
Contaminants,
Ecology,
Humic substances are the predominant form of natural organic matter (NOM) in soil and water and comprise the major pools of biologically refractory organic carbon and nitrogen in the biosphere. Humic substances play a role in almost all geochemical processes affecting soil and water. Knowledge of the formation and mineralization pathways of soil and aquatic humic substances is therefore critical to an understanding of the biogeochemical cycles of carbon and nitrogen, and climate change. Humic substances act as electron donor-acceptor systems and thus participate in oxidation –reduction processes with transition metal ions and biological systems in soil and water environments. Chlorination and chloramination of...
Direct and indirect ecological effects of the widely used insecticide bifenthrin on stream ecosystems are largely unknown. To investigate such effects, a manipulative experiment was conducted in stream mesocosms that were colonized by aquatic insect communities and exposed to bifenthrin-contaminated sediment; implications for natural streams were interpreted through comparison of mesocosm results to a survey of 100 Midwestern streams, USA. In the mesocosm experiment, direct effects of bifenthrin exposure included reduced larval macroinvertebrate abundance, richness, and biomass at concentrations (EC50s ranged 197.6 – 233.5 ng bifenthrin/ g organic carbon) previously thought safe for aquatic life. Indirect effects...
Direct and indirect ecological effects of the widely used insecticide bifenthrin on stream ecosystems are largely unknown. To investigate such effects, a manipulative experiment was conducted in stream mesocosms that were colonized by aquatic insect communities and exposed to bifenthrin-contaminated sediment; implications for natural streams were interpreted through comparison of mesocosm results to a survey of 100 Midwestern streams, USA. In the mesocosm experiment, direct effects of bifenthrin exposure included reduced larval macroinvertebrate abundance, richness, and biomass at concentrations (EC50s ranged 197.6 – 233.5 ng bifenthrin/ g organic carbon) previously thought safe for aquatic life. Indirect effects...
“Under section 303(d) of the 1972 Clean Water Act, states, territories, and authorized tribes are required to develop lists of impaired waters. These impaired waters do not meet water quality standards that states, territories, and authorized tribes have set for them, even after point sources of pollution have installed the minimum required levels of pollution control technology. The law requires that these jurisdictions establish priority rankings for waters on the lists and develop TMDLs for these waters” (U.S. Environmental Protection Agency, 2011). Waterways represented in this data set are a subset of these EPA 303 (d) listed streams that were classified as nutrient impaired. Nutrient impaired streams include...
This dataset summarizes impairment status for HUC12 watersheds at the CONUS scale using the EPA publicly available Assessment, Total Maximum Daily Load (TMDL) Tracking and Implementation System (ATTAINS) geospatial package and the USGS Watershed Boundary Dataset (WBD). ATTAINS is an online system maintained by the EPA containing information about the condition of the Nation’s surface waters, as reported by individual states. These data were downloaded in October 2023 and primarily reflect 2022 stream conditions. Because of the varying data types that exist in the database, an independent methodology was developed for summarizing impairment status for HUC12 watersheds using the USGS WBD as detailed in this metadata...
Key Findings Tree swallows were sampled at 6 locations in the Maumee River watershed, as part of a collaborative four-agency study on ecosystem effects of contaminants of emerging concern (CECs) on biota. This study involved samples of sediment, benthic invertebrates, and an insectivorous bird, the tree swallow. Endpoints include assessment of changes in both the tree swallow metabolome and transcriptome to determine whether perturbations can be traced from ToxCaste, an in vitro water sample assessment through mussels/clams, fish, and birds. Avian tissues and food will be analyzed for CECs with an emphasis on agricultural pesticides. Other Great Lakes’ landscape types will be sampled in future years. Products...
The diversion of freshwater from the Mississippi River is intended to mitigate saltwater intrusion from the Gulf of Mexico and to lessen the concomitant loss of wetland areas. Though effective, freshwater diversion can affect wildlife and habitat; therefore, prediversion and postdiversion data collections are necessary to identify effects. The Davis Pond freshwater diversion area is located between the Mississippi River and Bayou Lafourche and extends to Barataria Bay Basin, Louisiana. Results and interpretations from the prediversion biomonitoring done in 2001- which included data on fish, eagles, and bivalves - are presented in the U.S. Geological Survey (USGS) Scientific Investigations Report 2008-5067, "Davis...
The diversion of freshwater from the Mississippi River is intended to mitigate saltwater intrusion from the Gulf of Mexico and to lessen the concomitant loss of wetland areas. Though effective, freshwater diversion can affect wildlife and habitat; therefore, prediversion and postdiversion data collections are necessary to identify effects. The Davis Pond freshwater diversion area is located between the Mississippi River and Bayou Lafourche and extends to Barataria Bay Basin, Louisiana. Results and interpretations from the prediversion biomonitoring done in 2001- which included data on fish, eagles, and bivalves - are presented in the U.S. Geological Survey (USGS) Scientific Investigations Report 2008-5067, "Davis...
To elucidate and quantitatively explain the behavior of hydrogeologic systems typically characterized by hydrogeologic and physics-based complexity and data scarcity, for purposes of developing theory when needed, and with a focus on practical management (use and preservation) of water-resource systems to benefit humankind.
Categories: Project;
Tags: Contaminants,
Groundwater Flow and Transport,
Groundwater Hydraulics,
Hydrogeology
Research goals are (1) to develop reaction-transport models with varying levels of complexity and data requirements, providing guidelines for the appropriate application of these models given field conditions and limited resources; (2) to incorporate the effects of surface-chemistry phenomena into reaction-transport modeling; (3) to develop methods to identify and quantify important chemical and biological reactions affecting transport of inorganic and organic substances; and (4) to compile estimates of reaction rates and reaction-rate laws for chemical and biological reactions. In addition to model development, the project undertakes field, laboratory, and theoretical studies to investigate field-scale chemical...
Improve understanding of physical and biogeochemical processes affecting water quality of groundwater and surface water. Research focus includes multidisciplinary field and laboratory studies to determine factors affecting sources, movement, and fate of nutrients and reactive inorganic contaminants in the hydrologic cycle. Improve the usefulness of stable isotopes and other environmental tracers in hydrology and biogeochemistry by developing new techniques and approaches. Research topics include analytical techniques for stable isotopes in compounds separated from groundwater and surface water, stable isotope forensics, enriched isotope tracer experiments to quantify transport and reaction rates, field and...
Categories: Project;
Tags: Biogeochemistry,
Contaminants,
Groundwater Flow and Transport,
Isotopic Tracers,
Nutrients,
Uranium mill tailings and related forms of low-level radioactive waste contain elevated contents of naturally occurring radionuclides that have been brought to the surface, processed for the recovery of uranium and/or other components and then disposed of in near-surface impoundments. The long-term fate of the tailings and their constituents will be determined by surficial earth processes. Project objectives are to study the chemical form in which radionuclides and selected stable elements are retained in surficial earth materials, particularly uranium mill tailings, and to identify processes operating in natural aqueous and terrestrial systems that may influence the transport of these constituents from these earth...
Human activities from climate change to waste discharges to water management are modifying ecosystems across the earth, often in ways that are not well understood. This project addresses the problem of better understanding changes in aquatic ecosystems as driven by human disturbances interacting with natural processes. More specifically, the project studies a) the mechanisms of biological and ecological response to stressors such as metal contamination, nutrient enrichment, physical habitat alteration, climate change, and introduced species, and b) the influence of species, communities, and ecosystem processes on the distribution, transport, and fate of chemical contaminants (e.g., metals, nutrients). Most studies...
Categories: Project;
Tags: Aquatic Habitat,
Contaminants,
Ecology,
Estuaries and Near-Shore Environments,
Metals,
As part of the continuing effort to collect baseline information on the environmental occurrence of pharmaceuticals, and other organic wastewater contaminants (OWCs) in the Nation's water resources, water samples were collected from a network of 47 groundwater sites across 18 states in 2000. All samples collected were analyzed for 65 OWCs representing a wide variety of uses and origins. Site selection focused on areas suspected to be susceptible to contamination from either animal or human wastewaters (i.e. down gradient of a landfill, unsewered residential development, or animal feedlot). Thus, sites sampled were not necessarily used as a source of drinking water but provide a variety of geohydrologic environments...
This is a multi-disciplinary community of scientists who study the effects of wildfire disturbance on the built and natural environment. The mission is to understand natural processes such as infiltration, rainfall-runoff, erosion, sediment and chemical transport, and water quality effects. The focus is on obtaining field-based measurements that can be used to improve or develop models for use by emergency, land and water supply managers as tools for decision making.
Direct and indirect ecological effects of the widely used insecticide bifenthrin on stream ecosystems are largely unknown. To investigate such effects, a manipulative experiment was conducted in stream mesocosms that were colonized by aquatic insect communities and exposed to bifenthrin-contaminated sediment; implications for natural streams were interpreted through comparison of mesocosm results to a survey of 100 Midwestern streams, USA. In the mesocosm experiment, direct effects of bifenthrin exposure included reduced larval macroinvertebrate abundance, richness, and biomass at concentrations (EC50s ranged 197.6 – 233.5 ng bifenthrin/ g organic carbon) previously thought safe for aquatic life. Indirect effects...
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