Source apportionment of mercury to the atmosphere from wildfires and other sources in the western USA

Mercury (Hg) is a toxic trace metal with globally distributed emissions, and the potential to bioaccumulate in terrestrial and aquatic animals. This dissertation characterizes source apportionment of Hg to the atmosphere with the goal of better understanding the global Hg cycle in order to mitigate the bioaccumulation of methylmercury in terrestrial and aquatic ecosystems.; Mercury emissions from wildfires in northwestern Wyoming and central Washington were investigated. Mercury release during wildfires of low to high fire severity were quantified based on comparisons of total soil Hg and foliage at unburned and recently burned forests. At the Rex Creek Fire (central Washington) we compare the results of this method with previous estimates of Hg release based on atmospheric sampling of Hg and CO in smoke. The discrepancy between these estimates suggest that they are measuring different components of Hg release during wildfires. We use the difference between these estimates to suggest that ∼1/2 of the Hg emitted was rapidly deposited locally downwind by scavenging of Hg by coarse particulates and impaction with rugged topography.; Source apportionment of Hg to Camp Davis, Wyoming was investigated. Total gaseous Hg (TGM), particulate Hg, particulate major and trace metals in ambient atmospheric particles, and wet Hg deposition were collected during two intensive summer sampling seasons in 2002 and 2003. Principal components analysis (PCA) of particulate data and back-trajectories of air masses indicate that easily eroded soils and exposed rock formations contribute in addition to a combination of production, wildfires, cement production together account for ∼1/4 of the pHg and TGM concentrations observed. The results of the PCA indicate the presence of a regional Hg source contributed ∼75% of the pHg and TGM in ambient air at Camp Davis.; We present the first high precision stable isotopic measurements of mercury isotopes (by MC-ICP-MS) in a series of soils, peats, and coals. The variety of sample types analyzed during this study have permitted a preliminary Hg mass balance, based on Hg isotopic compositions, and indicate that approach will be useful in identifying the pathways by which Hg is distributed on the Earth's surface.