Geochemical and microbial characteristics of seepage water and mineral precipitates in a radwaste disposal facility impacted by seawater intrusion and high alkalinity

Baknoon Ham, Jang Soon Kwon, Maxim I. Boyanov, Edward J. O'Loughlin, Kenneth M. Kemner, Man Jae Kwon

Research output: Contribution to journalArticlepeer-review

Abstract

The construction of an underground facility can dramatically change the quality, flow direction, and level of groundwater. It may also impact subsurface microbial composition and activity. Groundwater quality was monitored over eight years in two observational wells near an underground disposal facility on the east coast of South Korea. The results showed dramatic increases in dissolved ions such as O2, Na, Ca, Mg, and SO4 during facility construction. Seepage water samples downgradient from the silos and tunnels, and precipitates deposited along the seepage water flow path were collected to determine the impact inside the disposal facility. X-ray analysis (powder X-ray diffraction (pXRD) and X-ray absorption fine structure (XAFS)) were used to characterize the mineral precipitates. Microbial community composition was determined by 16S rRNA gene sequencing. The seepage water composition was of two types: Ca–Cl and Ca–Na–HCO3. The ratio of Cl and δ18O showed that the Ca–Cl type seepage water was influenced by groundwater mixed with seawater ranging from 2.7% to 15.1%. Various sulfate-reducing bacteria were identified in the Ca–Cl type seepage water, exhibiting relatively high sulfate content from seawater intrusion. Samples from the Ca–Na–HCO3 type seepage water had an extremely high pH (>10) and abundance of Hydrogenophaga. The precipitates observed along the flow path of the seepage water included calcite, ferrihydrite, green rust, and siderite, depending on seepage water chemistry and microbial activity. This study suggests that the construction of underground structures creates distinct, localized geochemical conditions (e.g., high alkalinity, high salinity, and oxic conditions), which may impact microbial communities. These biogeochemical changes may have undesirable large-scale impacts such as water pump clogging. An understanding of the process and long-term monitoring are essential to assess the safety of underground facilities.

Original languageEnglish
Article number112087
JournalJournal of Environmental Management
Volume285
DOIs
Publication statusPublished - 2021 May 1

Keywords

  • Microbial community compositions
  • Mineral precipitates
  • Radwaste disposal site
  • Seepage water
  • Underground silo disposal facility

ASJC Scopus subject areas

  • Environmental Engineering
  • Waste Management and Disposal
  • Management, Monitoring, Policy and Law

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