Global and Local Sources of Mercury Deposition in Coastal New England Reconstructed from a Multiproxy, High-Resolution, Estuarine Sediment Record

Historical reconstruction of mercury (Hg) accumulation in natural archives, especially lake sediments, has been essential to understanding human perturbation of the global Hg cycle. Here we present a high-resolution chronology of Hg accumulation between 1727 and 1996 in a varved sediment core from the Pettaquamscutt River Estuary (PRE), Rhode Island. Mercury accumulation is examined relative to (1) historic deposition of polycyclic aromatic hydrocarbons (PAHs) and lead (Pb) and its isotopes (Pb-206/Pb-207) in the same core, and (2) other reconstructions of Hg deposition in urban and remote settings. Mercury deposition in PRE parallels the temporal patterns of PAHs, and both track industrialization and regional coal use between 1850 and 1950 as well as rising petroleum use after 1950. There is little indication of increased Hg deposition from late 19th-century silver and gold mining in the western U.S. A broad maximum of Hg deposition during 1930-1980, and not found in remote sites, is consistent with the predicted influence of additional industrial sources and commercial products. Our results imply that a significant portion of global anthropogenic Hg emissions during the 20th century was deposited locally, near urban and industrial centers of Hg use and release.