Characterization and control of behavior of microbial community in subsurface soil environment during the in situ bioremediation

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In situ bioremediation has attracted attention as a useful technology for clean up the contaminated soil. For in situ bioremediation, it is essential to understand and control distribution, transportation, and activities of microbial community. However, the behavior of microbial community in subsurface soil has not been well documented. Thus, this study aimed 1)to examine the microbial community structure in subsurface soil several meters below the ground surface, 2)to monitor the changes in microbial community structure during the natural attenuation using a field lysimeter contaminated with petroleum hydrocarbons, and 3)to examine the transport of microbial cells through porous media. This study will provide useful information to the in situ bioremediation1)Microbial community structure in subsurface soilStructures of microbial community were examined for upland yellow soil profile, river sand profile, and seashore profile using respiratory quinone profile. The microbial biomass and … More diversity decreased as the increase in depth. However, there are spots with a high biomass and diversity in subsurface soil where carbon content was high. The community structures in subsurface soil were similar among the soil profiles.2)Changes in microbial community structure during natural attenuation of petroleum hydrocarbonsA field lysimeter under an unsaturated condition was contaminated with petroleum hydrocarbons, and changes in the structure of microbial community in the contaminated soil was monitored using respiratory quinone profiles over 1 year. Petroleum hydrocarbons transported downward in lysimeter by infiltration water. Specific quinone species increased when petroleum hydrocarbon concentration increased to 3000 mg/kg at maximum, indicating propagation of the degrading microorganisms. After petroleum hydrocarbons dissipated, community structure returned to the one before the contamination.3)Microbial transport through porous mediaTransport of microbial cells by infiltration water was examined using a Sho-na-i river soil as a microbial source and glass beads as porous media. A high flow rate of infiltration water resulted in the transport of soil particles, which showed a positive correlation with microbial cells transported, but not in the case of low flow rate. There were differences among the proportions of free and attached bacterial cells between the high and low flow rates of infiltration water. Less