Sites with atmospheric mercury concentration data used in this analysis shown as larger white circles with 3-character site abbreviation, described in 2. Mercury Deposition Network (MDN) sites with wet deposition measurements shown as smaller colored symbols, Classification of MDN sites into Great Lakes (GL) or other regional categories was made on simply on a State and Provincial basis, i.e., if site was in State or Province adjacent to one or more GL, it was classified as a GL site. Only MDN sites with essentially complete data for 2005 were used in the analysis.