HR: 0830h
AN: B21D-0750    [PDF]
TI: Exacerbation of Atmospheric Mercury Emissions From Substrates by Atmospheric Oxidants
AU: * Engle, M A
EM: mark.engle@ttemi.com
AF: Env. and Res. Sci., Univ. of Nevada, Mail Stop 370, Reno, NV 89557 United States
AU: Gustin, M S
EM: msg@nevada.unr.edu
AF: Env. and Res. Sci., Univ. of Nevada, Mail Stop 370, Reno, NV 89557 United States
AU: Lindberg, S E
EM: LindbergSE@ornl.gov
AF: Env. Sci. Div., Oak Ridge National Lab., Oak Ridge, TN 37831 United States
AU: Gertler, A W
EM: alang@dri.edu
AF: Atmos. Sci. Div., Desert Research Institute, Reno, NV 89512 United States
AB: Previous studies have identified a variety of meteorological parameters such as incident radiation and temperature, which appear to control the temporal variations and magnitude of Hg emissions from natural substrates. New datasets show variations in Hg emissions over time which differ significantly from meteorological changes suggesting that other mechanisms control Hg emissions. This study investigated the potential control of atmospheric oxidants on Hg emission from substrates. In this laboratory-based study, emissions of elemental Hg (Hg$^{o}$) and reactive gaseous Hg (RGM) were measured from 5 substrates in Hg and oxidant free air (zero air), O$_{3}$ enriched (50 ppb) zero air, and ambient air. The experiments were conducted in a temperature-controlled environment with no light. Results showed a 2-4 order of magnitude increase in both Hg$^{o}$ emissions and RGM concentrations in ambient air and O$_{3}$ enriched zero air relative to emissions in zero air for all 5 substrate samples. Significant relationships (p$<$0.05) between ambient O$_{3}$ concentrations and Hgo emissions were also observed. This suggests that atmospheric oxidants, and possibly some other components in ambient air, facilitate Hg emission from soil. The proposed mechanism for this reaction is the physical displacement of Hgo from the substrate surface by O$_{3}$. Experiments using only Hg$^{o}$$_{(g)}$ and O$_{3}$ demonstrated that the increased RGM concentrations associated with experiments employing soils were not an effect of homogenous gas-phase oxidation of Hg. The increased RGM concentrations are therefore due to 1) physical displacement of the RGM by O$_{3}$ or; 2) heterogenous oxidation of Hg$^{o}$ on the soil surface. An important implication of this work is that increasing concentrations of O$_{3}$ and other atmospheric oxidants since the industrial revolution may have triggered an increase of atmospheric Hg emissions and re-emissions from natural substrates during the same time period.
DE: 0400 Biogeosciences
DE: 1030 Geochemical cycles (0330)
DE: 1045 Low-temperature geochemistry
DE: 1610 Atmosphere (0315, 0325)
SC: Biogeosciences [B]
MN: 2003 Fall Meeting