Isotopic composition of atmospheric mercury

The isotopic composition of species-specific atmospheric mercury (Hg) was investigated in the coastal environment of Grand Bay, Mississippi, USA. Hg0(g), HgII(g) and Hg (p) were concurrently separated and collected, and subsequently analyzed for isotopic composition. Hg0(g) displayed negative mass dependent fractionation (MDF) with a range > 3.5 ‰ (delta 202Hg = -3.88 ‰ to -0.33‰). Hg(p) displayed intermediate MDF (delta202Hg = -1.61‰ to -0.12‰), while HgII(g) displayed positive MDF (delta202Hg = +0.51‰ to +1.61‰). Significant positive mass independent fractionation was observed in Hg(p) (Delta199Hg = +0.36‰ to +1.36‰), while Hg0(g) displayed negative MIF (Delta199Hg = -0.41‰ to -0.03‰) and HgII (g) displayed intermediate MIF (Delta199Hg = -0.28‰ to 0.18‰). Positive MIF of 199Hg and 201Hg measured in Hg(p) points to significant in-aerosol photoreduction. Significant MIF of 200Hg was observed in all Hg species with Hg0(g) displaying negative Delta200Hg values of -0.19‰ to -0.06‰ and Hg(p) and HgII(g) displaying positive Delta200 Hg values of +0.06‰ to +0.28‰.