My research interests are in analytical and environmental chemistry; more precisely, method development of passive sampling devices, evaluation of factors affecting the bioavailability of contaminants in soils, as well as the extraction and instrumental analysis of contaminants in traditionally difficult matrices. For example, I receive deceased animals, tissue samples, regurgitations, etcetera from around the country and South America for the determination of insecticide poisoning. Mass transport, environmental fate, and trace analysis of contaminants are also of great interest. Most analytical expertise is in the extraction, separation, and quantitation of contaminants from various matrices. Primary instrumentation has been gas and liquid chromatography coupled with numerous detectors, as well as atomic absorption spectroscopy (flame, graphite furnace, and hydride generation).
General Overview of My Research:
Collaborative research, whether amongst students, between faculty and students, or between faculty at other Institutions, is quite effective and can allow for a more thorough analysis of the “question” being evaluated. While working at Clemson University, I had the opportunity to collaborate with a number of researchers, both faculty and students, on a variety of projects. Most projects had a field component coupled with laboratory studies (analytical methods, contaminant fate, toxicity, etc.). Although I did work on the field studies, my primary responsibility usually was in the development of novel methods for the extraction and analysis of various contaminants and their metabolites. For example, a project in collaboration with USGS evaluated the effectiveness agricultural best management practices (till versus no-till) on non-point source pollution in a Tennessee watershed. My role was to develop extraction methods for the insecticide being studied, aldicarb and its oxidative metabolites (aldicarb sulfoxide and aldicarb sulfone), from both soil and water. Others then used these methods to process hundreds of samples and were able to determine that no-till farming caused greater amounts of contaminated run-off. I also worked with faculty, staff, and students on several other projects, among them: pollutant source identification in an urban stream after storm events; development of methods to evaluate pesticide distributions, analytically and biochemically, in Costa Rican banana plantations; evaluation of the distribution of chlorpyrifos between water and an aquatic macrophyte (Elodea densa); evaluation of the sub-lethal effects of chlorpyrifos on the freshwater invertebrate, Daphnia.magna, using pulsed contaminant exposures; and evaluation of mechanisms of organophosphate (OP) toxicity in European starlings using non-lethal methods of detecting and/or monitoring OP exposure to wildlife.
Contaminant Bioavailability and Toxicity Assessment
My laboratory is investigating the development of sampling and analysis techniques and their use in addressing environmental questions. Since my arrival at SlUE, I have maintained a productive research group, and am collaborating with faculty here, Kansas State University, Southern Illinois University Carbondale, Texas Tech University (where I am an adjunct faculty member) and the University of Tennessee at Chattanooga. One of the first collaborative efforts with TTU was a project using raccoons (Procyon lotor) as sentinels for polychlorinated biphenyl and heavy metal exposure and effects at a gaseous diffusion plant. The goal was to determine the extent of raccoon exposure to PCBs and heavy metals at the site and reference areas through residue analysis of target tissues (brains, livers, kidneys, fat, milk, food items, hair); to determine the extent of adverse effects on environmental contamination in raccoons through biomarker endpoints (P-450, porphyrinogenesis, and possibly immunocompetence); and to evaluate the spatial distribution (through radio-telemetry) of contaminant exposure and effects in raccoons as seen through residue analysis and biomarker endpoints. I serve on several committees where I help students validate their analytical techniques to support their research and interpret their results. Today, we are working on potential insecticide exposure to various organisms.
My laboratory is investigating the development of sampling and analysis techniques and their use in addressing environmental questions. My students and I are actively studying the use passive sampling devices to estimate soil contaminant concentrations. Through numerous studies we have investigated several theoretical relationships between sampler levels and soil concentrations, and then validated them in five field studies.
The overall emphasis is to correlate PSD contaminant levels with measured and bioavailable levels. Studies are being conducted to evaluate how contaminant aging and sorption effect PSD uptake. Soil toxicity tests are being conducted to determine contaminant toxicity to earthworms (Eisenia Foetida) as a function of time or aging. Then both PSDs and worms will be evaluated simultaneously to determine correlations in uptake in each with aging. Additionally, the PSD field calibration method is going to be more rigorously tested by multiple comparisons of actual versus predicted soil concentrations, and bioavailability correlations will be evaluated concurrently both in the laboratory and in situ.
The development of a sampling device that reduces costs and uncertainties in site assessments will greatly aid in remedial decisions. It is my intent to develop and evaluate a sampling device that will yield quantitative estimates of both actual and bioavailable contaminant levels with one sample at the site of contamination. This will allow for measured and bioavailable contaminant profiles to be integrated into more focused remedial efforts based on the actual risks of contaminants at sites. In addition, sites can be identified in which bioremediation technologies will be effective. We will be comparing and contrasting both PSD and earthworm uptake in field studies, at our experimental plot on campus, and at contaminated sites in Chattanooga. In addition, we are evaluating the effect of contaminant aging on changes in toxicity as measured by LD50s and critical body residues (CBRs). We are also in the early phases of field evaluations of CBRs.
Other Research Areas:
Ecological Risk Assessment: South Chattanooga, TN
The people living in South Chattanooga are largely minority and impoverished. For decades, they have voiced concern about health effects due to living in South Chattanooga. Their proximity to these dumps and exposure from periodic flooding warrants concern. This concern is further substantiated by the recent detection of PAHs and metals in their yards, community gardens, playgrounds, and school grounds. To address the concerns, our research aims to: measure the potential for exposure to PAHs and metals by quantifying these toxicants in the soil; measure the biological availability of PAHs and metals by quantifying these toxicants in tissues of small mammals; measure exposure by quantifying biological indicators in small mammals; measure the effects of exposure by quantifying PAH-DNA adducts in small mammals; and Quantify the potential for the residents of South Chattanooga to be exposed and affected by PAHs and metals present in area soil by using the data generated in this study in a probabilistic risk assessment.
Non-Point Source Pollution
In preliminary studies that we have conducted (Parker and Johnson, unpublished data), results indicate that under certain vegetative filter strip management practices, over time, the filter strip may lose its effectiveness (i.e. the filter strip has reached its capacity to remove pollutants). As such, there is a need to better understand how differing vegetation types, design and management practices can effect the overall efficacy of vegetative filter strips. One of the initiatives of this area of research is to determine the efficacy of VFSs employing differing vegetation and management practices to remediate point and non-point source contamination. To accomplish this, studies will be conducted that: Determine the effectiveness of the filter strip as a function of the length of the filter strip; Determine the effect of season on the performance of vegetative filter strip system (i.e. the vegetative status in early spring vs. mid-summer vs. late fall); Under worse case scenario (i.e. saturated soil and high water flow), determine the effectiveness of the vegetative filter strip as indicated by an indicator pollutant; Determine the effectiveness of the vegetative filter strip in removing a variety of water contaminants; Determine the effectiveness in nitrate or agrochemical removal (depending on site), in VFSs with two vegetation management practices; and Determine the effectiveness of at least two vegetation types (or mixtures thereof) for the removal of selected contaminants from water.
The goal of these studies is to evaluate the feasibility of using constructed wetland systems for the treatment of urban contaminated runoff. In the initial phase of the study, laboratory simulation experiments will be conducted in a wetland microcosm system (Fraser and Keddy, 1997; Lin et al., 2002). The specific research objectives are: 1) to determine the extent to which the constructed wetland microcosm removes heavy metals and PAHs from urban runoff; 2) to elucidate the pathways and fate of heavy metals and PAHs in the simulated aquatic ecosystem; and 3) to explore the mechanisms that control the remediation efficiency of urban wastewaters by wetlands.
Speciation of Phytovolatilized Organoasrinical Compounds
This study will identify and quantify the dominant chemical forms of volatile arsenic that are produced by soil microbes and plants (for different plant species). The findings from this study are crucial for us to develop and promote a cost-effective and environmentally sound biotechnology (phytoremediation and/or phytovolatilization) for the management of arsenic contaminated soil and water. Additionally, the outcome from these studies should yield a new novel analytical technique, as well as information regarding the speciation of volatile arsenic compounds. To the best of our knowledge (Interagency Phytoremediation Program meeting, 2004), this is the first attempt to characterize volatile arsenic compounds produced by plants and soil microbes.
Wildlife Exposure to Contaminants
Ecotoxicity of Migratory Birds: Organophosphate and Carbamate Insecticide Impacts
In this study exposure of migratory shorebirds to organophosphorus and carbamate pesticides will be monitory. Study sites will include stopover sites in the Central Flyway of the United States and wintering sites in Brazil and Argentina. Within stopover and wintering regions, birds will be sampled in control areas unlikely to have contaminants (internationally or federally protected wildlife areas) and agricultural areas likely to have pesticide use (e.g., rice fields, pastures, sod fields). The study species will include shorebirds associated with both upland and wetland habitats. Organophosphorus and carbamate pesticides are widely used pesticides that have replaced more persistent organochlorines such as DDT. Both classes represent a major threat to nontarget wildlife because they have a range of sub-lethal and lethal effects, primarily through cholinesterase (ChE) inhibition. Cholinesterase activity in body tissues indicates recent exposure (24-48 hours) to OP and CB pesticides. The majority of samples collected will be ethanol footwashes for insecticide analysis and blood samples taken from live birds captured in mistnets, but a few birds will be collected at sites where live capture is difficult or if pesticide mortality incidents should occur. ChE activity and reactivation assays will be used to measure cholinesterase activity in blood plasma and brain tissues. Levels of OP and CB exposure to migratory shorebirds are currently unknown. This research will be used to evaluate habitat quality at important wintering and migration sites, and to develop conservation efforts aimed at reducing the impacts of pesticides on neotropical migrant shorebirds.