Mercury isotope signatures in contaminated sediments as a tracer for local industrial pollution sources.

Mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) may cause characteristic isotope signatures of different mercury (Hg) sources and help understand transformation processes at contaminated sites. Here, we present Hg isotope data of sediments collected near industrial pollution sources in Sweden contaminated with elemental liquid Hg (mainly chlor-alkali industry) or phenyl-Hg (paper industry). The sediments exhibited a wide range of total Hg concentrations from 0.86 to 99 μg g–1, consisting dominantly of organically-bound Hg and smaller amounts of sulfide-bound Hg. The three phenyl-Hg sites showed very similar Hg isotope signatures (MDF δ202Hg: −0.2‰ to −0.5‰; MIF Δ199Hg: −0.05‰ to −0.10‰). In contrast, the four sites contaminated with elemental Hg displayed much greater variations (δ202Hg: −2.1‰ to 0.6‰; Δ199Hg: −0.19‰ to 0.03‰) but with distinct ranges for the different sites. Sequential extractions revealed that sulfide-bound Hg was in some samples up to 1‰ heavier in δ202Hg th...