Isotope investigation of mercury sources in a creek impacted by multiple anthropogenic activities

To investigate mercury (Hg) sources responsible for contamination at Gumu Creek in South Korea, Hg concentration (THg) and Hg isotope ratios were measured in the soil and sediment of Gumu Creek and the samples from a hazardous waste landfill (HWL). The THg ranged between 0.29-327 mg kg^-1 and 9.5-414 mg kg^-1 in the soil and sediment, respectively, reflecting heterogeneous distribution and elevated levels across the entire Gumu Creek. Without the soil with the lowest THg (0.30 ± 0.01 mg kg^-1, n = 3), the δ²⁰²Hg (-0.83 to -0.18‰) and Δ¹⁹⁹Hg (-0.24 to 0.01‰) of the sediment and soil of Gumu Creek were within the ranges of the HWL samples (δ²⁰²Hg; -1.29 to -0.38‰, Δ¹⁹⁹Hg; -0.31 to 0.01‰). The comparison with the literature reporting sediment Hg isotope ratios impacted by various anthropogenic Hg sources revealed a presence of diverse Hg sources at Gumu Creek, including commercial liquid Hg, phenyl-Hg, and fly ash, consistent with the types of waste deposited within the HWL. Using commercial liquid Hg, fly ash, and the soil with the lowest THg as end-members, the ternary mixing model yielded 25-88% and 12-57% contributions from commercial liquid Hg and fly ash to the Gumu Creek sediment, respectively. The results of our study suggest that Hg isotope ratios are an effective tool for screening potential Hg sources at sites where the distribution of Hg is heterogeneous and multiple anthropogenic activities exist.