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INVESTIGATING OXIDATION MECHANISMS OF HGO IN THE FREE TROPOSPHERE AND ITS INFLUENCE ON LONG RANGE MERCURY TRANSPORT
Citation:
LANDIS, M. S., R. J. STEVENSON, AND G. J. KEELER. INVESTIGATING OXIDATION MECHANISMS OF HGO IN THE FREE TROPOSPHERE AND ITS INFLUENCE ON LONG RANGE MERCURY TRANSPORT. Presented at International Conference on Mercury, Madison, WI, August 06 - 11, 2006.
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:
ORD initiated automated speciated mercury measurements at the NOAA Mauna Loa Observatory (MLO), a high altitude research station (~11,500 feet) in 2001. Mercury monitoring at MLO was supplemented with trace element aerosol, criteria gas, and gas and particulate halide measurements. Observations at MLO are consistent with aircraft results suggesting that there is a significant Hg0 oxidation mechanism at altitude. These observations are not consistent with the contemporary conceptual atmospheric mercury model that estimates the Hg0 atmospheric lifetime to be approximately 1 year.