Impact of climate change on mercury concentrations and deposition in the eastern United States

Abstract

The global–regional climate–air pollution modeling system (GRE-CAPS) was applied over the eastern United States to study the impact of climate change on the concentration and deposition of atmospheric mercury. Summer and winter periods (300days for each) were simulated, and the present-day model predictions (2000s) were compared to the future ones (2050s) assuming constant emissions. Climate change affects Hg2+ concentrations in both periods. On average, atmospheric Hg2+ levels are predicted to increase in the future by 3% in summer and 5% in winter respectively due to enhanced oxidation of Hg0 under higher temperatures. The predicted concentration change of Hg2+ was found to vary significantly in space due to regional-scale changes in precipitation, ranging from −30% to 30% during summer and −20% to 40% during winter. Particulate mercury, Hg(p) has a similar spatial response to climate change as Hg2+, while Hg0 levels are not predicted to change significantly. In both periods, the response of mercury deposition to climate change varies spatially with an average predicted increase of 6% during summer and 4% during winter. During summer, deposition increases are predicted mostly in the western parts of the domain while mercury deposition is predicted to decrease in the Northeast and also in many areas in the Midwest and Southeast. During winter mercury deposition is predicted to change from −30% to 50% mainly due to the changes in rainfall and the corresponding changes in wet deposition.