Mercury isotope variations in surface soils in different contaminated areas in Guizhou Province, China

Guizhou Province is known as a heavily Hg-polluted area in China due to its special geochemical background and complicated Hg emission sources. In this study, we investigated the Hg isotope compositions of surface soil samples in the Hg mining area, zinc smelting area, coal combustion area, which are known to be the typical pollution regions of Hg in this province. We also compared the Hg isotopic fingerprints of primary Hg sources, such as hydrothermal Hg-bearing ores, coals and atmospheric Hg samples. According to our study, Hg stored in surface soils in different pollution regions in Guizhou Province displays a wide range of both mass dependent fractionation (MDF, δ²⁰²Hg) and mass independent fractionation (MIF, Δ¹⁹⁹Hg). δ²⁰²Hg varies by 2.0‰ and Δ¹⁹⁹Hg varies by 0.25‰ in the investigated surface soils. This study demonstrated that using a “MDF-MIF” two dimensional Hg isotope system could be particularly useful in discriminating Hg sources in soils.