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Monitoring Mercury Speciation and Reaction in Utility Emission Plumes

Project Leads and Affiliations:

Mathew Landis and Jeff Ryan, EPA/Office of Research and Development

Key Collaborators:

Winston Luke, National Oceanic and Atmospheric Administration
Praveen Amar, North East States for Coordinated Air Use Management (NESCAUM)

Project Abstract Written: October 2005

Project Timeframe: 2006 - 2008

Project Summary:

When mercury is emitted from a source, its fate and transport depends upon its chemical form or speciation. Divalent reactive gaseous mercury (RGM) and particle bound mercury tends to deposit locally or regionally, while elemental gaseous mercury (Hg0) tends to travel greater distances before being deposited. Recent studies by electric utility companies have suggested that RGM in coal-fired utility boiler emission plumes rapidly converts to Hg0, therefore minimizing the amount of local and regional atmospheric deposition. This hypothesized reaction would potentially have significant implications for how we manage mercury emissions from coal-fired utilities. However, there remains significant scientific uncertainty in methodologies and assumptions that lead to this controversial hypothesis. In addition, recent EPA studies have shown that coal-fired utility boiler emissions do significantly impact local and regional mercury deposition. This proposal seeks to determine the existence of such a reaction in coal-fired utility boiler emissions plumes, and if found quantify the extent of conversion of RGM to Hg0. We propose to achieve these research goals by taking simultaneous speciated mercury measurements in a coal-fired utility boiler stack and in the emission plume using an airborne sampling platform.

The EPA recently finalized the Clean Air Mercury Rule (CAMR) for electric utilities. The uncertainty surrounding potential local scale impacts resulting from the cap and trade approach in CAMR may continue to be a significant issue in the near term. This project will provide critical scientific information to gain a better understanding of this issue. The product of this pilot project will be a report that summarizes the results of the coordinated stack and in-plume measurements campaign. This report will have significant implications for our understanding of the local, regional, and global fate and transport of mercury emitted from coal-fired utility boilers and will provide a stronger scientific-basis for the decisions of policy makers. Results from this pilot project may also be incorporated into mercury fate and transport models that will be used to analyze mercury policy in the future.

Note - Process of selecting a field site for the utility plume monitoring was concluded in 2007; Northern Florida.

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