Mercury contamination in the riparian zones along the East Fork Poplar Creek at Oak Ridge

Oak Ridge (Tennessee, USA) has a history of mercury (Hg) contamination in its aquatic and soil environment associated with past nuclear-weapons production activities at its Department of Energy (DOE) sites. Three different riparian zones along the Lower East Fork Poplar Creek were investigated in order to study Hg distribution and transformation in surface soils. The surface soil samples collected from these areas showed higher total Hg on an average (129.08 mg/kg) and higher total organic carbon (5.50%) in the upstream soils compared to the other two downstream locations that contained only 31.78 and 19.98 mg/kg total Hg and 2.88% and 1.65% of TOC on average, respectively. Further, methyl Hg concentrations were also comparatively higher in case of the upstream soils (30.10 μg/kg) than that of the downstream sites (5.69 and 4.05 μg/kg). The study showed a plume-like dispersion of Hg in the terrestrial environment along the creek, with decreasing Hg concentrations with distance from the Hg source zone. Also, the transformation of Hg in the soils was found to have been influenced by the soil TOC contents.