Mercury Isotope Investigations of Pre-and Post-Industrial Atmospheric Deposition

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ABSTRACTReports from widely separated areas of the Earth have revealed a hemispherical, if not global, accumulation of mercury in the environment. While it is clear that atmospheric deposition plays a major role, and that perhaps as much as half of the annual release of mercury into the atmosphere is anthropogenic in origin, important details of the mercury cycle and fluxes are uncertain.There are six naturally occurring isotopes of mercury. Certain physical, chemical and biochemical processes produce slight separations (fractionation) of these isotopes. As a consequence, the isotopic composition of environmental mercury can potentially provide key constraints to models of mercury cycling and fluxes. Since the degree of isotope fractionation during a process like condensation of atmospheric mercury is temperature dependent, the isotopic composition of mercury recorded in well-dated material such as peat cores might also provide information on paleoclimate.Recent developments make it possible to make very precise measurement of mercury isotope ratios and these measurements have revealed differences in the isotopic composition of mercury ores and industrially processed mercury. This project is designed to test the feasibility of applying mercury isotope systematics to environmental mercury and to develop routine techniques (by improving existing techniques) for high-precision, isotope-ratio measurements at environmental levels. In order to be able to demonstrate the feasibility, a peat core that archives a well-studied record of atmospheric mercury deposition is selected as sample material.