HIGH-RESOLUTION CHRONOLOGY OF MERCURY AND ITS ASSOCIATION WITH POLYCYCLIC AROMATIC HYDROCARBONS (PAHS) AND LEAD ACCUMULATION IN A VARVED ESTUARINE SEDIMENT CORE

Natural archives such as lake sediments and polar ice sheets have been critically important to the understanding, modeling, and assessment of major biogeochemical cycles, climate variability, and impacts of inorganic and organic contaminants. Here we present a high-resolution chronology of mercury (Hg) accumulation between 1822 and 1996 as determined in a well-studied sediment core from the Pettaquamscutt Estuary in Rhode Island, northeast U.S. These results for Hg in this scrupulously dated, varved repository (1–3 y resolution) provide a quantitative means for assessing the magnitude, timing, and relative source strengths of human-related Hg emissions and deposition over this 174 year period. The significance of these findings will be examined (1) relative to other temporal reconstructions of Hg deposition, especially those obtained using dated lake sediment cores, and (2) to the historical depositional patterns of polycyclic aromatic hydrocarbons (PAHs), and lead (Pb) isotopes that have been determined in the same core. Broadly, Hg accumulation in sediment of the Pettaquamscutt Estuary parallels the temporal patterns of PAHs, which track growth in industrialization and coal use between 1850 and 1950, as well as increased use of oil after 1950. There is no suggestion of a North American Hg signal predicted to be associated with extensive gold and silver mining in the western U.S. between 1850 and 1900. The question of whether Hg accumulating in the estuary is derived primarily from local or more regional sources will be explored given the importance of atmospheric deposition in the environmental cycling of Hg and Pb.