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ATMOSPHERIC MERCURY DEPOSITION TO LAKE MICHIGAN DURING THE LAKE MICHIGAN MASS BALANCE STUDY
Citation:
Landis, M S. AND G. J. Keeler. ATMOSPHERIC MERCURY DEPOSITION TO LAKE MICHIGAN DURING THE LAKE MICHIGAN MASS BALANCE STUDY. ENVIRONMENTAL SCIENCE & TECHNOLOGY 36(21):4518-4524, (2002).
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:
Wet and dry mercury (Hg) deposition were calculated to Lake Michigan using a hybrid receptor modeling framework. The model utilized mercury monitoring data collected during the Lake Michigan Mass Balance Study and the Atmospheric Exchange Over Lakes and Oceans Study together with high-resolution over-water meteorological data provided by the National Oceanic and Atmospheric Administration (July, 1994 - October, 1995). Atmospheric deposition was determined to be the primary pathway for mercury input to Lake Michigan, contributing approximately 84% of the estimated 1403 kg total annual input (atmospheric deposition + tributary input). Wet (10.6 ug m-2) and dry deposition (9.7 ug m-2) contributed almost equally to the annual atmospheric Hg deposition of 20.3 ug m-2 (1173 kg). Reemission of dissolved gaseous Hg from the lake was also significant (7.8 ug m-2), reducing the net atmospheric deposition to 12.5 ug m-2 (720 kg). A strong urban influence was observed in the over-water mercury deposition estimates in the southern portion of the lake. The Chicago/Gary urban area was estimated to contribute approximately 20% (127 kg) of the annual atmospheric mercury deposition to Lake Michigan. The magnitude of local anthropogenic mercury sources in the Chicago/Gary urban area suggests that emission reductions could significantly reduce atmospheric mercury deposition into Lake Michigan.
The U.S. Environmental Protection Agency through its Great Lakes National Program Office (Grants GL985742-01-1 and GL 985430-01-2) funded the research described here under to the University of Michigan Air Quality Laboratory (UMAQL). 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.