Isotopic composition of atmospheric mercury

Abstract

The isotopic composition of species-specific atmospheric mercury (Hg) was investigated in the coastal environment of Grand Bay, Mississippi, USA. Hg⁰_(g), Hg^II_(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 ‰ (δ ²⁰²Hg = −3.88 ‰ to −0.33‰). Hg_(p) displayed intermediate MDF (δ²⁰²Hg = −1.61‰ to −0.12‰), while Hg^II_(g) displayed positive MDF (δ²⁰²Hg = +0.51‰ to +1.61‰). Significant positive mass independent fractionation was observed in Hg_(p) (Δ¹⁹⁹Hg = +0.36‰ to +1.36‰), while Hg0_(g) displayed negative MIF (Δ¹⁹⁹Hg = −0.41‰ to −0.03‰) and Hg^II _(g) displayed intermediate MIF (Δ¹⁹⁹Hg = −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 Δ²⁰⁰Hg values of −0.19‰ to −0.06‰ and Hg_(p) and Hg^II_(g) displaying positive Δ²⁰⁰ Hg values of +0.06‰ to +0.28‰.