Dong-Chan Koh

Application of cluster analysis for the hydrogeochemical factors of saline groundwater in Kimje, Korea

The main hydrogeochemical characteristics of shallow groundwater in the coastal area at Kimje city, Korea, have been identified in the present study. From cluster analysis, the groundwater in the study area is classified into four groups (A, B, C, and D). Groundwaters in B, C, and D groups are strongly affected by the present seawater and the trapped old seawater because the area including B, C, and D groups contacts the Yellow Sea and contains the reclaimed land. They also are governed by reduction processes. On the other hand, groundwater in group A has been largely affected by chemical fertilizers because its land has been used for the agricultural activities for a long time. As groundwater flows from group A to group D according to its path, the governing factor of the groundwater quality gradually tends to change from chemical fertilizers into reduction processes and seawater intrusion.

Molecular analysis of spatial variation of iron-reducing bacteria in riverine alluvial aquifers of the Mankyeong River.

Alluvial aquifers are one of the mainwater resources in many countries. Iron reduction in alluvial aquifers is often a major anaerobic process involved in bioremediation or causing problems, including the release of As trapped in Fe(III) oxide. We investigated the distribution of potential iron-reducing bacteria (IRB) in riverine alluvial aquifers (B1, B3, and B6 sites) at the Mankyeong River, Republic of Korea. Inactive iron reduction zones, the diversity and abundance of IRB can be examined using a clone library and quantitative PCR analysis of 16S rRNA genes. Geobacter spp. are potential IRB in the iron-reducing zone at the B6 (9 m) site, where high Fe(II) and arsenic (As) concentrations were observed. At the B3 (16 m) site, where low iron reduction activity was predicted, a dominant clone (10.6%) was 99% identical in 16S rRNA gene sequence with Rhodoferax ferrireducens. Although a major clone belonging to Clostridium spp. was found, possible IRB candidates could not be unambiguously determined at the B1 (18 m) site. Acanonical correspondence analysis demonstrated that, among potential IRB, only the Geobacteraceae were well correlated with Fe(II) and As concentrations. Our results indicate high environmental heterogeneity, and thus high spatial variability, in thedistribution of potential IRB in the riverine alluvial aquifersnear the Mankyeong River.