Use of membranes and detailed Hysplit analyses to understand particulate, gaseous oxidized, and reactive mercury chemistry

Abstract

The atmosphere is the primary pathway by which Hg enters ecosystems. Despite the importance of atmospheric deposition, concentrations and chemistry of gaseous oxidized (GOM) and particulate (PBM) Hg are poorly characterized. Here the use of 3 membranes in tandem (cation exchange (CEM), nylon, and polytetrafluoroethylene (PTFE) membranes) was used as means for quantification of concentrations and identification of the chemistry of GOM and PBM. Detailed Hysplit analyses was done to determine sources of oxidants forming RM. Despite the coarse resolution of sampling (1-to-2 weeks) a gradient in chemistry was observed with halogenated compounds dominating over the Pacific Ocean and continued influence from the marine boundary layer in Nevada and Utah, and a periodic occurrence in Maryland. Oxide based RM compounds arrived at continental locations via long range transport. Nitrogen, sulfur, and organic RM compounds were due to regional and local air masses. Concentrations were highest over the ocean and decreased moving from west to east across the United States. Comparing concentrations on membranes with and without PTFE in front demonstrated CEM provide a quantitative measure of RM concentrations. This method is viable for understanding the chemistry of GOM and PBM compounds.