1. Mercury Concentrations, Precipitation, and Mercury Wet Deposition in the Great Lakes Region, 2001 - 2008 by Martin Risch 1, David Gay 2, Kathleen Fowler 1, Gerard Keeler 3, Pierrette Blanchard 4, and Sean Backus 4 1 U.S.Geological Survey 2 University of Illinois 3 University of Michigan 4 Environment Canada

2. OBJECTIVE Prepare a summary of annual atmospheric mercury concentrations and wet deposition in the Great Lakes region by integrating data from monitoring programs in US states and Canada for 2001-2008.

3. PURPOSES Quantify baseline conditions for comparison with future mercury reductions from emissions- control regulations. Display spatial patterns of annual atmospheric mercury concentrations and wet deposition through a time series of regional maps.

4. METHODS Great Lakes Region: 9 states in USA, 2 provinces in Canada Hg concentration data from 37 sites: 31 MDN, 4 UMAQL, 2 CAMNET Precipitation data from 1,757 sites in National Weather Service and Canadian Weather Service cooperative observer programs GIS map-grid technique for isopleth maps 75 percent complete annual record required

7. METHODS contd Mercury wet deposition typically more related to precipitation amount than to mercury concentration. More sites with precipitation data than sites with mercury data. Grid-map isopleth of annual concentrations + points with annual precipitation = points with annual wet deposition  deposition isopleth.

8. Preliminary Data for Discussion Only July 2010

9. Annual Precipitation-Volume- Weighted Mercury Concentrations in Samples, nanograms per liter

10. Preliminary Data for Discussion Only July 2010

13. Annual Precipitation, in centimeters per year

14. Preliminary Data for Discussion Only July 2010

17. Annual Mercury Wet Deposition in micrograms per square meter per year

18. Preliminary Data for Discussion Only July 2010

21. PLANS FOR DISCUSSION Changes in concentration, deposition, and precipitation, 2001-2008. Influences on areas of high deposition: - Precipitation vs. concentration; - Trends in precipitation and concentration; - Emissions sources and source controls. Direct deposition to Great Lakes waters.