OPTically‐based In situ Characterization System (OPTICS) to quantify concentrations and mass fluxes of mercury and methylmercury in South River, Virginia, USA

Abstract

AbstractHistorical releases of mercury to the South River (Virginia, USA) and mobilization of mercury from secondary sources (e.g., riverbed and riverbank sediments) is contributing to the redistribution of mercury to the water column. Therefore, in order to effectively remediate the South River, it is necessary to understand specific mechanisms for mercury contamination and transport in the system. An OPTically‐based In situ Characterization System (OPTICS) monitoring study was conducted to quantify concentrations and mass fluxes of mercury and methylmercury and to understand mechanisms of contaminant exchange between sediments and the water column. Storm flow and diel cycling (potentially related to nocturnal bioturbation activities) were identified as important mechanisms of particulate‐phase mercury and methylmercury exchange to the South River water column. It was determined that diel cycling contributed daily average mass transport of 0.01 kg of particulate mercury and 1.9E‐05 kg of particulate methylmercury, representing up to 13% and 16% of total mercury and methylmercury mass transported over the study period. Approximately 85% of the 3.6 and 0.01 kg total mass transport of particulate mercury and methylmercury over the study period was attributed to high storm flow, which likely resulted in resuspension of particle‐bound mercury and methylmercury and/or mobilization of fine‐grained channel margin deposits.