Browsing by Author "Damian Shea, Committee Member"

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Bioaccumulation of Platinum Group Metals in the Freshwater Mussel Elliptio Complanata
(2009-04-15) Mays, Jason Warren; W. Gregory Cope, Committee Co-Chair; Thomas J. Kwak, Committee Co-Chair; Damian Shea, Committee Member
ABSTRACT MAYS, JASON WARREN. Bioaccumulation of Platinum Group Metals in the Freshwater Mussel Elliptio complanata. (Under the direction of Thomas J. Kwak and W. Gregory Cope). The use of catalytic converters for automobile exhaust purification has led to emission and environmental contamination by the platinum group metals (PGM) platinum (Pt), palladium (Pd), and rhodium (Rh). In this study, a total of 37 sites were sampled throughout central North Carolina and were chosen based on availability of the freshwater mussel Elliptio complanata, varied geographic distribution, land use patterns, and vehicle traffic density. At each site, a sample of sediment and three adult E. complanata were collected from within 50-150 m both upstream and downstream of the road crossing. Mussel tissue and sediment samples were analyzed for concentrations of Pt, cadmium (Cd) and mercury (Hg). Related stream and local variables investigated included sediment total organic carbon, water chemistry, and estimated vehicle traffic density at the bridge. Landscape variables included human population density, land use, and density of transportation infrastructure. Pt concentrations in mussel tissue ranged 0.09-1.98 ng/g dry weight and 0.06-1.86 ng/g dry weight in sediment among sites. A biota sediment accumulation factor for Pt, calculated as the mean [tissue]/[soil], was 3.2, compared to 87 and 88 for Hg and Cd, respectively. Pt contamination of mussels and sediment at highway crossing sites were not significantly correlated with the amount of traffic crossing the specific structure. Rather, multiple regression modeling indicated a significant relation between Pt concentration in mussels at a site and the human population of the watershed. A 28-d laboratory test was conducted with waterborne Pt and Pd to determine toxicity, bioaccumulation, and to assess several potential biomarkers of exposure to Pt and Pd. Test mussels were exposed to five concentrations of an equal mixture of Pt and Pd salts, ranging from 0.05 to 500 ÃŽÂ¼g/L of each metal, in a static renewal test. The 500 Ã‚Âµg/L concentration resulted in high mortality (4 of 9 dead by day 12) of test mussels; all individuals in each of the other test concentrations survived to the end of the test. There were nine replicate mussels per treatment concentration, allowing three mussels from each treatment to be sampled on days 7, 14 and 28. Tissue and hemolymph were assessed for concentrations of Pt, Pd, sodium (Na+), calcium (Ca2+), potassium (K+), and chloride (Cl-) concentrations. Na+,K+-ATPase activity was assessed in gill tissue as a potential biomarker of exposure. Tissue concentrations of Pt ranged from 0.10 ng/g dry weight in controls to 34,486 ng/g dry weight in the 500 Ã‚Âµg/L treatment, and Pd ranged from 0.06 ng/g dry weight in controls to 34,404 ng/g dry weight in the 500 Ã‚Âµg/L treatment. Concentrations of Pt in hemolymph ranged from 0.08 ng/mL in controls to 50.1 ng/mL in the 500 Ã‚Âµg/L treatment, and Pd ranged from 0.06 ng/mL in controls to 12.2 ng/mL in the 500 Ã‚Âµg/L treatment. On day 28, Na+,K+-ATPase activity displayed a logarithmic trend (y=0.489ln(x)+2.054; R2=0.73) of increasing activity with increasing PGM exposure concentration; however, activity was only significantly increased (P<0.05) at 5.0 Ã‚Âµg/L and 50 Ã‚Âµg/L concentrations. High variation and weak correlation of Na+,K+-ATPase activity with Pt and Pd exposure concentration indicate that it may not be a suitable biomarker of PGM exposure. Hemolymph Ca2+ concentrations were increased on day 7 at the 50 Ã‚Âµg/L concentration. Hemolymph Na+ levels were decreased on day 28 at the 5.0 Ã‚Âµg/L and 50 Ã‚Âµg/L concentrations. Cl- and K+ levels were decreased at the 50 Ã‚Âµg/L concentration. Tissue Pt and Pd concentrations in mussels exposed to the lowest test concentration (0.05 Ã‚Âµg/L) displayed tissue concentrations of Pt that were approximately six times greater than the maximum tissue concentrations measured in stream-sampled mussels. Hemolymph ion measurement does not appear to be sensitive enough to serve as a biomarker of PGM exposure at environmentally relevant exposure concentrations. Results from this study will provide resource managers with information on this emerging group of contaminants needed to perform risk assessments for transportation impacts to natural systems and to develop conservation, protection, and mitigation plans for this critically imperiled faunal group.
Delineating Sources and Estimating Cadmium Bioaccumulation and Susceptibility Differences among Aquatic Insects.
(2007-10-29) Martin, Caitrin Anne; David Buchwalter, Committee Chair; Gerald LeBlanc, Committee Member; Damian Shea, Committee Member
Human activities such as mining and smelting have altered the distribution of trace metals in the environment, resulting in trace metal pollution of aquatic ecosystems worldwide. Trace metal contamination has been shown to adversely affect benthic macroinvertebrate community structure by influencing species diversity, density and abundance. Aquatic macroinvertebrates play integral roles in stream ecosystem function and are widely used in biomonitoring programs as indicators of stream integrity. Relative to marine and other lentic invertebrates, lotic insects are grossly underrepresented in ecotoxicological studies. A major challenge in ecotoxicology lies in generating data under experimental conditions that are relevant to understanding contaminant effects in nature. Biodynamic modeling is one laboratory-based approach for understanding trace metal bioaccumulation in a number of aquatic invertebrates. This approach combines species-specific physiological traits associated with metal bioaccumulation from both aqueous and dietary sources to make predictions of metal- and species-specific bioaccumulation that compare well relative to field-based measurements. This thesis represents the first application of biodynamic modeling to stoneflies, a dominant insect group in North American streams. A second goal of these comparative studies was to determine how much variability, or conversely, predictability there is in some of the physiological processes related to bioaccumulation. Because insects as a group are so species rich, a comprehensive testing regime is unfeasible. These comparative studies were designed to determine if closely related taxa share physiological characteristics such as cadmium uptake rate from solution, elimination rate, and subcellular compartmentalization of accumulated metal. Biodynamic models were generated 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 Cd concentrations. It has become increasingly evident that diet plays a major role in the accumulation of metals in aquatic invertebrates and the importance of diet is consistent in stoneflies. Diet was the predominant source of accumulated Cd in five of the seven species and averaged 53.2 ± 9.6 % and 90.2 ± 3.7% of the total Cd accumulated in perlids and perlodids, respectively. These results are relevant to water quality criteria that are often based on toxicity tests involving aqueous exposures only. Differences in Cd bioaccumulation between the two families were largely driven by differences in dissolved uptake rates, which were considerably slower in perlodids than in perlids. Cadmium uptake rates also varied within families, suggesting that family level generalizations about metal accumulation may be erroneous. We further examined the subcellular compartmentalization of cadmium accumulated from dissolved and dietary exposures. Predicted steady state concentrations were modified to only consider Cd accumulated in potentially susceptible subcellular compartments. These values ranged 5.3 fold. This variability is discussed within a phylogenetic context as well as its implications for bioassessment.
In Vitro Cardiotoxicity of Residual Oil Fly Ash.
(2006-07-18) Knuckles, Travis; Kenneth Adler, Committee Chair; Philip Sannes, Committee Member; Damian Shea, Committee Member; Kevin Dreher, Committee Member
Epidemiological studies have shown an association between air pollution particulate matter (PM) and adverse cardiovascular effects. Although numerous mechanisms have been proposed, the actual mechanism(s) as well as emission sources and associated causal properties by which PM affects the cardiovascular system remain elusive. At least some adverse PM health effects can be attributed to bioavailable constituents, most notably, the transition metal content of the particles. Toxicological studies in rats using residual oil fly ash (ROFA) combustion source particles show extrapulmonary effects ranging from thermo-regulatory alterations, myocardial necrotic lesions, to fatal cardiac arrhythmias. Exposure of rats to ROFA via intratracheal instillation shows a rapid and transient increase in plasma metal content as early as 15mins post-exposure, suggesting that PM constituents are bioavailable to both the systemic circulation and perfused organs. However, the impact of this systemic exposure on extrapulmonary organs at the cellular and molecular levels is unknown. In this study, cardiomyocytes derived from 1-day-old rat pups were exposed to determine the direct effects of a particle free residual oil fly ash leachate (ROFA-L). Using concentration of leachate relevant to amount that were found in the plasma of rats following pulmonary deposition, I have shown that ROFA bioavailable constituents cytotoxicity in cardiomyocyte cultures and alter cardiomyocyte gene expression and transcription factor activation profiles consistent with alteration in cardiomyocyte growth and function.
Pesticide Residues in Surface Waters of North Carolina Rural and Urban Watersheds: Studies to Determine and Reduce Residues in Drinking Water.
(2004-09-03) Jones, Samantha Jane; Damian Shea, Committee Member; Ross B. Leidy, Committee Chair; Robert E. Holman, Committee Member; David Danehower, Committee Member
The practice of using pesticides on agriculture, commercial landscapes, residential lawns, highway rights-of-way, and recreational areas such as golf courses has resulted in non-point source contamination of surface waters via runoff. Assessment of human health implications of non-point sources within watersheds involved residues of selected pesticides monitored from 1999 to 2001 in surface waters that serve as drinking water sources of five rural and urban watersheds in North Carolina. Approximately 1500 samples from 90 sites were screened with Enzyme-Linked Immunosorbent Assay (ELISA) for atrazine, alachlor, simazine, chlorpyrifos, chlorothalonil, metolachlor, and 2,4-D. The residue concentrations exceeding 1.0 μg/L were extracted with C18 Empore™ Disks and analyzed by gas chromatography/nitrogen phosphorous detection (GC/NPD) for confirmation. The seven compounds showed similar pesticide concentrations in both rural and urban watersheds. The rural watersheds most often exhibited residues of atrazine, simazine, and 2,4-D while metolachlor and 2,4-D were chiefly found in urban areas. Pesticides intermittently exceeded established maximum contaminant levels (MCL) and led to further monitoring of raw and finished waters of treatment plants within the watersheds. Atrazine, simazine, metolachlor, 2,4-D residues were found in pre- and post-treated water at comparable levels, indicating little change in pesticide concentrations following standard treatment procedures. Remediation efforts focused on prevention of non-point sources of atrazine in a rural watershed. Atrazine residue levels were lowered as a result of source prevention implementation with the cooperation of municipalities, farming community, and county agricultural extension agents. The prevention measures involved alternatives to atrazine applications and utilizing either less-persistent pesticides or genetically modified seed. Additional remediation efforts involved the adsorbent ability of powdered activated carbon (PAC) as a treatment method for reducing pesticide residues in drinking water supplies. Studies with PAC combined with water fortified with a pesticide mixture of atrazine, chlorpyrifos, simazine, and metolachlor exhibited declines in residues from 25 to 100% of initial concentrations with 10 mg/L of carbon. Aluminum sulfate (alum) was combined with PAC in studies with atrazine and metolachlor to determine effects of contact time on the adsorption of the pesticide residues. Carbon alone adsorbed 5 to 30% more pesticide residues than carbon and alum combined and alum alone had minimal effects on residues of atrazine and metolachlor. Further carbon studies simulated treatment plant procedures to determine effective points of PAC addition within the treatment train of a model drinking water treatment plant. A carbon concentration of 20 mg/L was most efficient in reducing pesticides residues and carbon added prior to or after alum resulted in adsorption of atrazine, metolachlor, simazine, and alachlor residues that was more effective than simultaneous addition of the two chemicals.