Over the last decade, significant progress has been made characterizing and quantifying anthropogenic and natural source atmospheric mercury (Hg) emissions. Primarily through the development and operation of the Mercury Deposition Network (MDN), spatial interpolation of wet Hg deposition has been generated for the U.S. and southern Canada. Comparison between locations of significant atmospheric mercury sources (e.g., coal-fired power plants, chlor-alkali plants, gold mining, etc.) and areas of high wet Hg deposition provide poor overlap. This talk discusses potential reasons for this spatial disconnect including, previously unquantified sources, mechanisms that produce elevated deposition in specific areas, and atmospheric chemical reactions which may prevent removal of Hg via wet deposition. The study will focus on findings from recent USGS research at warm, coastal sites in Alabama, South Carolina, and Puerto Rico. [Mark’s email address = engle@usgs.gov]