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A SYNTHESIS OF PROGRESS AND UNCERTAINTIES IN ATTRIBUTING THE SOURCES OF MERCURY IN DEPOSITION
Citation:
LINDBERG, S., R. BULLOCK, R. EBINGHAUS, D. ENGSTROM, X. FENG, W. F. FITZGERALD, N. PIRONNE, E. PRESTBO, AND C. SEIGNEUR. A SYNTHESIS OF PROGRESS AND UNCERTAINTIES IN ATTRIBUTING THE SOURCES OF MERCURY IN DEPOSITION. AMBIO. Royal Swedish Academy of Sciences, Stockholm, Sweden, 36(1):19-32, (2007).
Impact/Purpose:
The objectives of this task are to continue development and improvement of EPA's mesoscale (regional through urban scale) air quality modeling systems, such as the Community Multiscale Air Quality (CMAQ) model, as air quality management and NAAQS implementation tools. This task focuses on needed research and development of air quality models targeted for a major CMAQ model release in FY08. Model development for a broad scope of application is envisioned. For example, CMAQ will need to be able to simulate air quality feedbacks to meteorology and climate as well as intercontinental transport. The 2008 release of CMAQ is timed to coincide with EPA/OAR's and the states' needs for an improved model for assessments of progress (mid-course corrections) in the post-SIP submittal timeframe.
Description:
A panel of international experts was convened in Madison, Wisconsin, in 2005 as part of the 8th International Conference on Mercury as a Global Pollutant. Our charge was to address the state of science pertinent to source attribution; specifically our key question was "For a given location, can we ascertain with confidence the relative contributions of local, regional and global sources, and of natural versus anthropogenic emissions, to mercury deposition?" The panel synthesized new research pertinent to this question published over the past decade, with emphasis on four major research topics: Long-term Anthropogenic Change, Current Emission and Deposition Trends, Chemical Transformations and Cycling, and Modeling and Uncertainty. The panel drew a series of conclusions within each topic which are presented in this paper. These conclusions led us to concur that the answer to our question is a "qualified yes," with the qualification being dependent upon the level of uncertainty one is willing to accept. We agreed that the uncertainty is strongly dependent upon scale and that our question as stated is answerable with greater confidence both very near and very far from major point sources, assuming that the "global pool" is a recognizable "source". Many regions of interest from an ecosystem-exposure standpoint lie in between, where source attribution carries the greatest degree of uncertainty.