Analysis of bacterial community structure in leachate-contaminated groundwater using denaturing gradient gel electrophoresis

This research has been performed to clarify the relationship between hydrogeochemistry and bacterial community structure in ground-water contaminated with landfill leachate. We collected and analyzed samples from 5 sites such as leachate (KSG1-12), treated leachate (KSG1-16), two contaminated groundwaters (KSG1-07 and KSG1-08) and non-contaminated groundwater (KSG1-13). pH was 8.83, 8.04, 6.87, 6.87 and 6.53 in order; redox potential (Eh) 108, 202, 47, 200 and 154 mV; electric conductivity (EC) 3710, 894, 1223, 559 and 169.9 μS/cm; suspended solids (SS) 86.45, 13.74, 4.18, 0.24 and 11.91 mg/L. In KSG01-12, the ion concentrations were higher especially in Cl^- and HCO ₃^- than other sites. The concentrations of Fe, Mn and SO₄^2- were higher in KSG1-07 than in KSG1-08, and vise versa in NO₃^2-. In the comparison of DGGE fingerprint patterns, the similarity was highest between KSG1-13 and KSG1-16 (57.2%), probably due to common properties like low or none contaminant concentrations. Otherwise KSG1-08 showed lowest similarities with KSG1-13 (25.8%) and KSG1-12 (27.6%), maybe because of the degree of contamination. The most dominant bacterial species in each site were involved in α-Proteobacteria (55.6%) in KSG1-12, γ-Proteobacteria (50.0%) in KSG1-16, β-Proteobacteria (66.7%) in KSG1-07, α-Proteobacteria (54.5%) in KSG1-08 and β-Proteobacteria (36.4%) in KSG1-13. These results indicate that the microbial community structure might be changed according to the flow of leachate in grounderwater, implying changes in concentrations of pollutants, available electron acceptors and/or other environmental conditions.