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THE EFFECTS OF THE COASTAL ENVIRONMENT ON THE ATMOSPHERIC MERCURY CYCLE
Citation:
Malcolm, E. G., G. J. Keeler, AND M S. Landis. THE EFFECTS OF THE COASTAL ENVIRONMENT ON THE ATMOSPHERIC MERCURY CYCLE. JOURNAL OF GEOPHYSICAL RESEARCH 108(D12):ACH4-1 to ACH4-9, (2003).
Impact/Purpose:
The overall research objective of this task is to improve our understanding of the emission, transport, transformation, and deposition of atmospheric mercury. Information garnered from this research is used to improve and evaluate EPA deterministic models that are used to investigate the (i) relative impact to local, regional, and global sources to atmospheric mercury deposition, and (ii) benefits of various emission reduction scenarios.
Specifically, individual research project objectives are listed below:
(1) Evaluate the ability of speciated mercury (Hg0, Hg2+, HgP) measurements to aid source apportionment models in identifying anthropogenic source contributions to atmospheric mercury deposition
(2) Elucidate the contribution of coal combustion sources to observed mercury wet deposition in the Ohio River Valley
(3) Obtain atmospheric profiles (200 - 12,000 ft) of speciated ambient mercury off the south Florida Coast
- Evaluate the role of long range transport of RGM to Florida in the marine free troposphere.
- Identify any vertical mercury gradients that might indicate the presence of rapid mercury chemistry in air or in cloud water.
(4) Conduct research at Mauna Loa Observatory to elucidate elemental mercury oxidation in the remote marine free troposphere.
(5) Conduct laboratory kinetics experiments to determine the rate constants of elemental mercury oxidation to gaseous inorganic divalent mercury species from atmospheric halide species (e.g. BrO, ClO).
Description:
Atmospheric mercury (Hg) species were investigated on the East Coast of Florida during June 2000. The site was impacted by air mass transport from the Atlantic Ocean and Southern Florida. Periods with atmospheric transport from the Atlantic were characterized by low concentrations of elemental gaseous Hg and inorganic divalent reactive gaseous Hg (RGM), demonstrating that the marine boundary layer was not a significant source of RGM to this coastal site as previous researchers have hypothesized. When anthropogenic impacts were observed at the site, indicated by elevated concentrations of gases including HNO3 and SO2, RGM concentrations had higher daytime maximums. Particulate phase Hg concentrations were higher than can be explained by sea spray alone, as determined by chemical analysis of the seawater, suggesting that gaseous Hg is diffusing to the sea salt aerosol. Although atmospheric Hg concentrations were not elevated, the observed scavenging of Hg gases by sea salt aerosols indicates that Hg may be rapidly cycled at the atmosphere-ocean interface between gaseous, aerosol and oceanic forms. Deposition of aerosol enriched in Hg via this process may constitute a significant global mercury flux to the oceans.
This work has been funded wholly or in part by the U.S. Environmental Protection Agency Office of Research and Development. It has been subjected to Agency review and approved for publication. Mention of trade names or commercial products does not constitute an endorsement or recommendation for use.