Date of Award
Doctor of Philosophy (PhD)
Peter van den Hurk, Committee Chair
The goal of this study was to develop a means of assessing and monitoring the potential impacts of complex mixtures in surface waters by utilizing environmentally representative mixtures collected using passive sampling devices and whole organism bioassays, which equally represent the complex biological systems they are acting on. Chemical monitoring across three watersheds and comprising seven sampling locations was conducted across Georgia and South Carolina using passive sampling devices (PSDs). Earlier research conducted in the lab showed differing, and significant responses from fish sampled at many of these sites using the ethoxyresorufin-O-deethylase (EROD) and glutathione S-transferase (GST) bioassays. The polar organic compound integrated sampler (POCIS) devices and low-density polyethylene (LDPE) strips were used to analyze for estrogens, pharmaceuticals and personal care products (PPCPs), PAHs, and PCBs. POCIS extracts were analyzed for four estrogenic compounds and seven PPCPs using Ultra-Performance Liquid Chromatography Mass Spectrometry tandem Mass Spectrometry (UPLC-MS/MS). Concentrations along the Savannah River were estimated to be at ng/L to sub-ng/L concentrations with seasonal trends identified for certain pharmaceuticals. PAH analysis was performed for the EPA Priority 16 using Gas Chromatography Electron Impact Mass Spectrometry (GC-EI/MS). PCB analysis was conducted for 128 congeners using GC-ECD. Total surface water concentrations (Cw) of PAHs ranged between 30-250 ppb and PCB concentration ranged between 5-12 ng PCBTOT/g PSD. Combined PSD extracts were used in small volume bioassays. The yeast estrogen screening (YES) assay was used to assess the overall estrogenicity of the surface water at the sampling sites, with estradiol equivalency quotients ranging between 2-10 ng/L. The zebrafish embryo developmental toxicity assay (ZEDTA) was utilized to link the measured chemical pollutants with observed biological effects. Biomarkers of exposure were favored to biomarkers of toxicity or other whole organism bioassays as a means of assessing organismal response to pollutant exposure. Epigenetic endpoints were chosen to identify exposure to endocrine disrupting compounds within mixtures. The methods optimized for this study assessed both whole-genome and region-specific CpG-island associated methylation levels of daphnia, whole body zebrafish embryos, and tissue-specific samples from adult zebrafish. Significant differences in methylation of CpG islands associated with endocrine related genes (ERÎ± and vtg1) were observed in response to EE2 and passive sampling extract exposures providing initial evidence for its application in assessing complex environmental mixtures.
Wyker, David C., "Pairing Passive Sampling with Epigenetic Biomarkers of Exposure to Monitor Potential Toxic Impact of Environmental Complex Mixtures" (2019). All Dissertations. 2467.