Summary of Accomplishments:

• Implementation of a combined numerical solution for gas-phase and aqueous-phase chemistry, including gas-aqueous interactions on short (<1 second) time scales, in the Community Model for Air Quality
• Addition of aqueous reactions for sulfates, nitrates, ozone, hydrogen peroxide, OH and related radicals, chlorine and mercury, along with reactions from a relatively complete mechanism for gas-phase chemistry. This also included Br and Cl chemical reactions in the full gas and aqueous phase chemical scheme.
• Application of the Hg model to a test case simulation for a model domain that included the eastern half of the U.S. and western half of the Atlantic Ocean (from 55 to 105 longitude).

As part of the project, a modified version of CMAQ has been developed that includes a numerical solution for combined aqueous and gas-phase chemistry. This combined solution accounts for the rapid exchange between gas-phase and aqueous-phase that take place within clouds, and has been tested in an inter-comparison of solutions for gas- and aqueous-phase chemistry (Barth et al., 2003).

Objective(s) of the Research Project

The project seeks to develop a 3-d Eulerian model for transport and photochemistry of mercury, including fully integrated gas-phase, aqueous and aerosol chemistry. An important goal is to develop detailed comparisons between model results and measurements from two field campaigns: a field campaign in south Florida which had aircraft measurements of Hg and an ongoing campaign being performed in the Great Lakes Region.

The project also seeks to use model results to investigate several research questions related to mercury: the impact of local emissions relative to transport from distant sources, the impact of photochemical processes, and the relative importance of cloud chemistry on the transformation, transport and deposition of mercury. A major objective will be to identify measurements that might provide evidence on these issues.

Publications/Presentations

Sillman, S., Marsik, F., Al-Wali, K.I., Keeler, G. J. and Landis, M. Models for the formation and transport of reactive mercury: Results for Florida, the northeastern U.S. and the Atlantic Ocean. To be presented at the Air Quality V: Mercury, Trace Elements, SO 4 and Particulate Matter Conference, Sept. 19-21, 2005.

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