Temporal changes of geochemistry and microbial community in low and intermediate level waste (LILW) repository, South Korea

Abstract

Microbes play a major role in affecting the radioactive wastes disposed of in underground wastes repositories. In particular, low- and intermediate-level waste (LILW) contains biodegradable constituents that can affect stability and mobility of radionuclides by the changes of geochemical conditions due to microbial activity. Despite these potential impacts, the bacterial communities in underground repository remain largely unexplored and previous studies have focused on the traditional culture-dependent methods. We examined the bacterial community in a large-scale in situ container packed with simulated waste in LILW underground repository of South Korea using 454 pyrosequencing. Taxonomic analysis showed the presence of Curvibacter, Azonexus, Pseudomonas, Novosphingobium, Acidovorax, and Victivallis as the dominant bacterial genera. Based on the thermodynamic and geochemical results, the precipitation of calcite was estimated to occur in the presence of genus Curvibacter. Although the flow rate of groundwater input had an impact on the bacterial communities, the community structure was resilient to the change of groundwater’s velocity. In addition, total Fe concentration, [Fetotal] was positively correlated to [Cl−] in this system. The temporal changes of geochemical parameters and bacterial communities provide insight for understanding of the microbial activity inside the large scale container and additional biogeochemical information for long-term risk assessment of disposal facility.