Doctoral Dissertation Research: Using Ice-Core Data to Reconstruct Atmospheric Mercury Deposition Over the Past 17,000 Years.

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The objective of this doctoral dissertation project is to reveal the natural and human controls on mercury deposition to northwestern North America. Human emissions of mercury, mostly from mining, smelting, and coal-burning, are currently rising, predominantly from Asia. The transport of mercury from Asia to northwestern North America may pose an emerging ecological and health hazard, contributing to already high levels of mercury in rivers and fish. However, in order to assess the impact of rising mercury pollution on the ecosystem, it is essential to also determine natural mercury levels through time, derived from volcanism, weathering, and forest fires. The Prospector Russell Col (PRCol) ice core, collected from the summit of Mt. Logan in the Yukon Territory of Canada in 2001 and 2002, is ideal for this study because of its location downwind from Asian pollution sources and its well-dated record spanning the past 17,000 years. This study will use clean sampling techniques and state-of-the-art analysis methods to measure mercury concentrations in the PRCol ice core at 1 to 100-year time scales. Mercury concentrations in this ice core will be compared to records of volcanic eruptions, forest fires, dust, and climate to determine the controls on natural changes in mercury levels. The impact of human mercury pollution on this region will be determined by comparing the concentrations of mercury deposited during the 20th century to concentrations deposited during the prior 17,000 years, before large-scale human mercury pollution. The influence of climate patterns such as El Nino on mercury transport and deposition will be investigated by comparing climate parameters and mercury concentrations during the 20th century.Determining the magnitude and trend of recent mercury contamination is a fundamental step in addressing the global issue of mercury pollution in the environment. Results of this research will be disseminated through academic publications and conferences. An undergraduate research assistant will be trained to assist in this research and to complete a related sub-project. The PIs will do outreach at local middle schools about their research, combining it with discussions of careers in the geosciences. International collaboration will be established through close work between the PIs and the Canadian researchers who collected and have already done some analysis of data derived from the ice core. As a Doctoral Dissertation Research Improvement award, this project will provide support to enable a promising graduate student to establish an independent researchcareer.