Collaborative Research: The Direct and Indirect Photolytic Fate of Persistent Organic Pollutants in Arctic Surface Waters

点击翻译按钮获取中文摘要

Abstract:Persistent organic pollutants (POPs) are capable of being transported to the Arctic by long-range processes (i.e., global distillation), and from locally contaminated areas by sea ice and runoff. The effect of these persistent pollutants on arctic ecosystems is poorly understood, but evidence shows that bioaccumulation occurs for some contaminants, and in particular may pose a threat to organisms at the highest trophic levels and indigenous people. Dissolved organic matter (DOM) is ubiquitous to all surface waters in the Arctic, and may play an important role in the fate of POPs. DOM is capable of acting as a "quasi-sorbent" thereby altering the speciation of POPs in the water column. DOM is also highly photoreactive and is able of forming chemical transients that can transform POPs to other substances. Given the high degree of photon flux that occurs during the boreal summer, photolytic processes may play an important role in POP fate in arctic surface waters. This research is exploring processes that control the fate of POPs in the presence of DOM from surface waters at a freshwater (Toolik Lake) and a marine site (Barter Island) in the Arctic. Specific objectives include:1. identify and quantify the level of POP contamination in the surface waters at the two sites;2. collect, isolate, and elucidate the structural and photolytic properties of DOM at these two sites;3. measure the degree to which direct and indirect photolysis occurs for POPs using solar simulators in the lab and at the Toolik Lake field site;4. identify and quantify the types and amounts of transient species formed by the photolysis of DOM; and5. study the reaction kinetics and mechanisms for the direct and indirect photolysis of POPs and their daughter products.The project is a collaborative effort between investigators at Ohio State University/BPRC (Chin) and the University of Colorado/INSTAAR (McKnight). Heptachlor, hexachlorobenzene, cis-chlordane, lindane, and two PCB congeners have been selected for study because they represent contaminants commonly detected in arctic surface waters, fauna, and the aboriginal people, and because they possess a wide range of physicochemical and photochemical properties. State-of-the-art methods for isolating and quantifying photosensitizers will be used. These include tangential-flow ultrafiltration unit and reverse-phase columns for concentrating DOM from the two sites. DOM isolates present at environmentally realistic levels will be used in both lab and outdoor photolysis experiments to determine the efficacy of these photosensitizers at transforming POPs. The reactions will be followed closely to quantify changes in both the parent compound and their photoderivatives. Other aspects of the project will attempt to "trap" phototransients using "probes" in an effort to elucidate important photolytic pathways. The proposed project will provide the basis for future research into the processes that control POP fate in the Arctic. Finally, information accrued will aid those parties responsible for the stewardship of these ecosystems.