Mercury distribution in poplar creek, Oak Ridge, Tennessee, USA

Abstract

AbstractAs a result of the lithium‐isotope separation process used in the production of thermonuclear fusion weapons during the mid‐1950s and early 1960s, 150 t of mercury were released into Poplar Creek (via East Fork Poplar Creek) in Oak Ridge, Tennessee, USA. This project was performed as part of a Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) remedial investigation to define the nature and extent of mercury contamination in Poplar Creek. Ultraclean sampling techniques and ultrasensitive analytical methods were used to determine methylmercury and inorganic mercury concentrations in surface water, sediment, and pore water from Poplar Creek. Total methylmercury and inorganic mercury concentrations (0.08–0.7 ng/L and 0.4–560 ng/L, respectively) in surface water from reaches downstream from the East Fork Poplar Creek confluence were significantly higher (p < 0.05) than the upstream reference reach (0.05–0.3 ng/L and 0.1–27 ng/L, respectively). Concentrations in surface water increased with distance downstream from the source (East Fork Poplar Creek), which was opposite of expected results. Sediment methylmercury and inorganic mercury concentrations also increased with the distance downstream from the source and were highest near the mouth of Poplar Creek (1.0–12 ng/g and 630–140,000 ng/g, respectively). High concentrations in surface water and sediment near the mouth of Poplar Creek appear to be a result of sediment deposition and resuspension, apparently caused by the stronger Clinch River current acting as a barrier and its backflow into Poplar Creek as a result of hydropower operations.