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ATMOSPHERIC MERCURY RESEARCH
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).
Environmental contamination from mercury has been recognized for decades as a growing problem to humans and wildlife. It is released from a variety of sources, exhibits a complicated chemistry, and proceeds via several different pathways to humans and wildlife. According to the 1997 Mercury Study Report to Congress, mercury deposition has increased by a factor of two to five over preindustrial levels. The most significant releases of mercury in the U.S. are emissions to the atmosphere as a result of human activities (i.e., anthropogenic), particularly the combustion of fuel containing trace amounts of mercury. Other sources of anthropogenic mercury include industrial processes and the disposal of products containing mercury.
While a plausible link has been made between mercury emissions and the presence of mercury in humans, a number of uncertainties related to both the risk assessment and risk management of mercury remains. The EPA ORD has developed a mercury research strategy which identifies seven key scientific questions that need to be addressed. EPA NERL/HEASD is presently focused on improving information on the transport, transformation and fate of mercury in the environment.