Fate of Organic Contaminants in Aquatic Environments: Contribution from Radio and Stable Isotope Chemistry
Abstract:
Many synthetic organic chemicals we use everyday contaminate our aquatic resources, and threaten the health of humans and ecosystems. Their adverse effects can be partially limited via the natural or artificially enhanced treatment capabilities of the environment.
In this seminar, I will discuss the ability of a constructed wetland and a forest buffer to remove pesticides in an agricultural catchment. I will present the results from a three-year long field study which demonstrated that both systems improved water quality. Such field-scale data do not allow understanding the dominant processes that account for the observed “percent reductions”. As a result, complementary laboratory experiments were conducted using wetland sediments, wetland plants, forest soil, and forest litter sampled on-site. On these substrates, 14C radio-labeled pesticides were used to study epoxiconazole (fungicide) degradation under flooded conditions as well as adsorption and desorption of isoproturon, metazachlor (herbicides) and epoxiconazole. The adsorption and desorption potential varied among the molecules and substrates, and epoxiconazole showed slow but possible degradation under anoxic conditions.
While effective, molecules labeled with radio-isotopes can only be used under highly controlled lab conditions. Stable isotopes are gaining popularity for investigating in situthe occurrence of natural degradation of molecules. I will illustrate this feature through two examples investigating the fate of chlorinated benzenes in a contaminated aquifer and in the sediment layer of a contaminated groundwater – surface water interface.
Short Biography:
Professor Elodie Passeport is cross-appointed in the departments of Civil Engineering, and Chemical Engineering and Applied Chemistry. She did her PhD at AgroParisTech and Irstea in France, and then moved to UC-Berkeley for a first Post Doctoral position in Professor Terry’s lab, and then to the University of Toronto in the Earth Sciences department for a second Post Doctoral position with Professor Sherwood Lollar. Her research group studies the fate and removal of contaminants from water, in natural and engineered environments. Her research is experimental and involves lab and field studies, and the development of analytical methods to determine concentrations and stable isotope signatures of organic contaminants.