Kolodziej, Edward PZhao, Haoqi Nina2022-01-262022-01-262021Zhao_washington_0250E_23639.pdfhttp://hdl.handle.net/1773/48224Thesis (Ph.D.)--University of Washington, 2021Human society discharges complex chemical mixtures into the aquatic environment that cause various adverse effects to aquatic organisms and humans. Upon discharge, organic chemicals typically form multiple transformation products (TPs) during abiotic and biotic environmental transformations. While many TPs are likely benign and unable to interact with biological pathways, some TPs can contribute significantly to the environmental risks of complex mixtures. There is a pressing need to identify stable and/or toxic TPs, to study their environmental fate and transport, and to evaluate the potential for TP toxicity in comprehensive risk assessments of environmental contaminants. In this thesis, we focused on the environmental transformations of two classes of organic contaminants: steroid hormone pharmaceuticals and industrial antiozonants used in tire rubbers. Specifically, project analytes include the photoproducts of trenbolone (TBOH) and altrenogest (ALT), compounds that occur in agricultural environments, and two synthetic progestins, dienogest (DIE) and drospirenone (DRO), that are contaminants of municipal wastewaters. These analytes represented novel steroid hormone pharmaceuticals that are potent and used widely but are less well characterized in the scientific literature. In addition, we focused on understanding the fate and transformation of 6PPD (N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine) and its structural analogues, which are globally ubiquitous antioxidants used in tire rubber and other consumer products. Our group recently identified 6PPD as a pre-toxicant responsible for the massive coho salmon (Oncorhynchus kisutch) mortality observed in the Pacific Northwest. For the above analytes, laboratory experiments were used to simulate environmentally relevant abiotic (e.g., photolysis, ozonation) and biotic transformation processes to (i) quantitatively analyze known TPs with liquid chromatography-tandem mass spectrometry (LC-MS/MS), (ii) determine the rate and extent of contaminant transformations, (iii) identify unknown TPs with high-resolution mass spectrometry (HRMS) based suspect screening and non-target analysis, and (iv) evaluate TPs bioactivity and environmental occurrence. Chapter 2 discussed a novel and sensitive analytical method for the detection and quantification of metastable TBOH and ALT photoproducts in agricultural receiving waters. The developed method employed solid phase extraction and LC-MS/MS analysis. Because commercial analytical standards are not available, reference standards for photoproducts were generated from TBOH or ALT with a solar simulator. With cold and pH neutral conditions, rapid sample processing, minimal extract storage, and reduction of cationic artifacts, we achieved efficient detection of the metastable photoproducts with method detection limits at the low ng/L ranges. The analytical method was then employed to evaluate the sorption of the steroid photoproducts in batch soil-water systems. We showed that the photoproducts exhibited reduced sorption affinity (logKoc of 1.92-2.57) relative to the more hydrophobic parent structures (logKoc of 2.46-2.76). Therefore, traditional runoff management practices in agroecosystems would be expected to exhibit reduced treatment effectiveness when the photoproducts were considered. Chapter 3 evaluated the biotransformation of ALT and its primary photo-cycloaddition product (ALT-CAP) in agricultural receiving waters and identified the TPs with HRMS. We showed that ALT-CAP (half-life, 1.6 days) demonstrated ~2-fold faster biotransformation than ALT (half-life, 3.5 days). However, the absolute abundance (based on electrospray ionization (ESI) HRMS peak areas) of the major ALT-CAP TPs, including dehydrogenation TPs, hydroxylation TPs, and isomerization TPs, was often an order of magnitude higher than that of ALT TPs. This indicated that biotransformation of ALT seemed to produce less abundant and less stable TPs, while ALT-CAP biotransformation tended to produce larger, and more stable TPs with higher potential for retained steroid structures. Therefore, the exposure risks of ALT are prone to underestimation if the formation and subsequent biotransformation products of ALT-CAP are not considered as part of the environmental fate of these compounds. In Chapter 4, we investigated the biotransformation of DIE and DRO with representative activated sludge batch incubations and identified relevant TPs using HRMS. We showed that DIE exhibited slow biotransformation (16-30 hr half-life), and proceeded through a quantitative aromatic dehydrogenation (molar yields ~55%) to form an aromatic TP ~30% estrogenic as 17β-estradiol. DRO experienced more rapid biotransformation (<0.5 hr half-life), and 1,2-dehydrogenation formed the major product (molar yields ~40%) as an anti-mineralocorticoid drug candidate named spirorenone. Lactone ring hydrolysis was another important biotransformation pathway for DRO (molar yields ~20%) and generated a pharmacologically inactive TP. Other minor pathways for DIE and DRO included hydroxylation, methoxylation, and 3-keto and C4(5) double bond hydrogenation; distinct bioactivities are plausible for such TPs, including anti-gestagenic activity, anti-gonadotropic activity, and pregnancy inhibition effects. These results demonstrated that biotransformation of DIE and DRO formed bioactive TPs in large quantities during wastewater treatment, which should be considered in future risk assessments of synthetic progestins. Chapter 5 focused on the identification and environmental fate of tire rubber-derived chemicals acutely toxic to coho salmon. Firstly, this chapter described the contribution of Nina Zhao to a large collaborative research project, led by Dr. Zhenyu Tian (postdoc scientist of our group), to identify the causal toxicant(s) for the coho salmon mortality from aqueous leachates of tire tread wear particles (TWPs). After initial purification of the TWP leachate by Dr. Tian, Zhao and Tian developed orthogonal HPLC fractionation steps that effectively separated the pure toxicant from ~600 chemicals in the purified TWP leachate. Thereafter, the coho toxicant was identified to be a highly toxic quinone TP of 6PPD formed during ozonation (i.e., 6PPD-quinone). This chapter then expanded this reaction pathway to analogue substituted-PPD antioxidants. Furthermore, this chapter explored the ozonation TPs of 6PPD beyond 6PPD-quinone with HRMS screening. Twenty-one potential TPs were identified, with five confirmed through reference standards and eleven with likely or probable structures proposed based on MS/MS spectra and literature information. The major 6PPD TPs were then retrospectively screened in archived sample extracts of TWP, TWP leachate, roadway runoff, and creek stormwater. We revealed widespread presence of 6PPD TPs in these sample matrices (ΣTPs: TWP methanolic extracts, 110 ± 7 µg/g; TWP leachate (0.25 g TWP/L water), 11 ± 2.7 µg/L; roadway runoff, 40 ± 15 µg/L; creek stormwater, 59 ± 20 µg/L). Overall, the results presented in this thesis confirmed our overall hypothesis that environmental transformations produced TPs that could contribute to residual biological activity in the aquatic environments. These TPs are discharged in large quantities and should be evaluated in future environmental risk assessments of the synthetic steroids and rubber antioxidants. More generally, holistic assessments of the environmental transformation processes are needed for future risk assessment of high potency environmental chemicals, in order to accurately assess the fate and exposure risks of these contaminants of emerging concerns.application/pdfen-USnoneEnvironmental engineeringEnvironmental scienceCivil engineeringThesis