Isotopic composition of species-specific atmospheric Hg in a coastal environment

The isotopic composition of species-specific atmospheric mercury (Hg) was investigated in the coastal environment of Grand Bay, Mississippi, USA. Atmospheric mercury species (Hg-(g)(0), Hg-(g)(II) and Hg-(p)) were collected individually, and analyzed for isotopic composition. Gaseous elemental Hg (Hg-(g)(0)) displayed delta Hg-202 ranging from -3.88 parts per thousand to -0.33 parts per thousand. Aerosol Hg (Hg-(p)) displayed intermediate delta Hg-202 ranging from -1.61 parts per thousand to -0.12 parts per thousand, while reactive gaseous Hg (Hg-(g)(II)) displayed positive delta Hg-202 ranging from +0.51 parts per thousand to +1.61 parts per thousand. Significant positive mass-independent fractionation (MIF) was observed in Hg-(p) (Delta Hg-199=+0.36 parts per thousand to +1.36 parts per thousand), while Hg-(g)(0) displayed negative MIF (Delta Hg-199=-0.41 parts per thousand to -0.03 parts per thousand) and He-(g)(II) displayed intermediate MIF (Delta Hg-199= -0.28 parts per thousand to 0.18 parts per thousand). Positive MIF of Hg-199 and Hg-201 measured in Hg-(p) is consistent with significant in-aerosol photoreduction. Significant MIF of Hg-200 was observed in all Hg species with Hg-(g)(0) displaying negative Delta Hg-200 values of -0.19 parts per thousand to -0.06 parts per thousand while Hg-(g)(II) and Hg-(p) displayed positive Delta Hg-200 values of +0.06 parts per thousand to +0.28 parts per thousand, which are similar to Delta Hg-200 values reported by Gratz et al. (2010). These results suggest that isotope tracing of each atmospheric Hg species may be feasible during important atmospheric processes such as wet and dry deposition. (C) 2012 Elsevier B.V. All rights reserved.