Environmental monitoring of low-level radioactive waste disposal in electrochemical plant facilities in Zelenogorsk, Russia

The concentrations of radionuclides, especially anions, in water can substantially exceed local background levels in the vicinity of former and currently operating uranium enrichment plants. In this study, we present new data on environmental monitoring near the uranium sludge collector of an electrochemical plant (ECP) in Krasnoyarsk Krai, Russia. We first tracked the complex biogeochemical processes that can affect the fate and transport of U in highly nitrate-polluted ground- and surface water. We described the main mechanisms of U immobilization: (a) biogenic and abiogenic reduction (microbial nitrate reduction caused dramatically Eh decrease), (b) sorption by organic matter in peat and by microbial biofilms on a sandy rock surface, and (c) precipitation with biogenic and abiogenic phases. The intensity of the biogenic and abiogenic factors depended on the dynamics of changes in the oxidation-reduction potential (ORP)-pH conditions as well as organic- and inorganic anion concentrations with distance from the source of pollution. Anammox bacteria were found in areas with high nitrate pollution, and we believe that they played a key role in lithotrophic nitrogen consumption and primary organic production. These data can form the basis for complex groundwater remediations close to U sludge repositories and can be implemented beyond the ECP site itself.