Advanced mercury isotope fractionation measurement to study the fate of mercury in the environment

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Mercury contamination poses a significant threat for human health and natural ecosystems at local, regional and global scales. Man-made mercury emissions have not only increased dramatically since pre-industrial times, but industrial activities also occasionally resulted in dramatic pollution at the local or regional scale. This element is a unique contaminant as contemporary anthropogenic emissions only represent a fraction of the entire environmental inventory. A significant proportion of mercury in the global cycle is of natural, geogenic origin. This creates considerable challenges for regulators tasked with managing mercury in the environment, and it would be desirable to distinguish natural from anthropogenic mercury sources. Thus, a detailed understanding of the biogeochemical cycle of mercury is essential, but not always sufficient. The measurement of stable mercury isotope ratios and determination of mercury isotope fractionation can aid to trace mercury from the pollution source to fish.The proposed research will develop new methods for measuring precise isotope ratios in methylmercury and apply the new technology in the field to establish the isotopic relationship between mercury in sediments and mercury in fish. Special focus will be on tracing legacy mercury that was historically discharged in the English-Wabigoon river system. We will establish the isotope fingerprint of mercury released from the chlor-alkali production source and monitor its spread throughout the Wabigoon River system and the community of Grassy Narrows. We will directly determine the mercury fingerprint of methylmercury in sediments, biota and water. Measurement of environmental samples will define a reference for the current mercury isotope ratio signature in sediments and fish of the Wabigoon-English River system. This contemporary baseline will serve as a check point for impending remediation activities that are due to commence in 2018/19. The technology will serve as a monitoring tool to monitor the efficacy of the remediation measures, which are planned to mitigate the currently high levels of mercury in fish.The proposed program will train a minimum of four graduates students, who will break new ground in providing accurate and precise and therefore defensible methods addressing the current challenge for scientists and regulatory agencies, which is to distinguish between geogenic and anthropogenic mercury in the environment. In the Canadian context, this work is particularly important for communities, where legacy mercury pollution has long been recognized, but where serious abatement plans are only now put into place. This research will help shaping policies for the future management of mercury in affected communities and other vulnerable ecosystems in Canada and the world.