YASUHARA Akio National Institute for Environmental Studies, Environmental Chemistry Division,, 化学環境部, 室長 (00101048)
NAKASUGI Osami National Institute for Environmental Studies, Regional Environment Division, Chi, 地域環境研究グループ, 上席研究官 (50109899)
|Budget Amount *help
¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1993 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1992 : ¥1,200,000 (Direct Cost : ¥1,200,000)
The remediation operation for subsurface environment is so costly, therefore, the success of the remediation totally depends on picking up the suitable techniques to repair the subsurface pollution, corresponding to contaminant existing form in subsurface environment. In this context, soil-gas survey as an option of remote geochemical exploration to identify the pollutant source to determine the sites for making boreholes was developed.
The remediation technologies employed in the pollution sites in Japan so far are the soil venting, groundwater extraction and soil excavation to physically remove the contaminants. All of them were applied to the study sites to evaluate the effectiveness and the application limit to the pollution scale. The result shows that the soil venting is so unique and useful to remove the volatile organochlorine from vadose zone. In the study sites, the groundwater extraction was also utilized. The comparison of both removal rates for trichloroethylene revealed th
at the removal rate by soil venting is one order as high as the groundwater extraction, and both removal rates are going down with operation time. The removal rates by soil venting is reducing more quickly than groundwater extraction, therefore, both removal rates are going to meet each other. After the crossing time, groundwater extraction will overcome the soil venting. In another pollution site, the polluted soil of up to 1,000m^3 under the building was excavated. After the operation, the groundwater extraction has continued to repair th aquifer and leads to uptake about twenty tons of trichloroethylene, reducing the groundwater concentration to near the drinkable limit. The organochlorines are basically little soluble in water so that the groundwater extraction needs fairly long time to repair the polluted aquifer. However, the groundwater extraction holds a possibility to remove much more contaminants, compared to the soil venting and soil excavation. The results obtained in this research mention that the groundwater extraction is inevitable technology for cleaning up the polluted aquifer.