Mercury (Hg) consumption through contaminated fish is one of the major pathways of human exposure to Hg. In this context, characterization of atmospheric Hg and understanding of processes that govern atmospheric concentration and deposition is important. Observations for the 2005-2009 time period from three Southeastern Aerosol Research and Characterization (SEARCH) air quality monitoring sites are examined for diurnal and seasonal variation in concentrations of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particle bound mercury (HgP < 2.5 mm). Three different sites are considered: 1) a suburban-coastal location near Pensacola, Florida (OLF), 2) an urban location in Birmingham, Alabama (BHM), and 3) a rural location west-northwest of Atlanta, Georgia (YRK). Analysis of diurnal and seasonal variation of speciated Hg concentrations for these sites will be discussed, especially the role of boundary layer processes in explaining the differences in temporal variation of surface Hg concentrations at these sites.
Recent studies of Holmes et al. (2008, 2010) found that Hg deposition associated with thunderstorm events to be higher compared to other types of precipitation events and that the enhanced wet deposition of Hg in the southeast United States (SEUS) is related to higher frequency of occurrence of thunderstorm in this region. Whereas Holmes et al. (2008, 2010) found enhancement in Hg deposition associated with thunderstorms in both SEUS and northeast United States (NEUS), the magnitude of enhancement was higher for the events in the southeastern region. In this context, the variability in thunderstorm morphology may be important of explaining the observed variability in Hg deposition in thunderstorm events. Impact of thunderstorm morphology on Hg deposition is examined using a conceptual framework that allows for systematic analysis of thunderstorm dynamics and microphysics as a function of environmental parameters that characterize thunderstorm evolution. Role of thunderstorm dynamics in determining Hg budget within cloud and rain water will be examined using analysis of idealized numerical simulation of thunderstorm evolution for environmental conditions characteristic of SEUS and NEUS regions.
