Natural Attenuation Pattern of Chlorinated Solvent at Yamagata Site in Japan

Y. Kawabe, E. Watanabe, M. Takeuchi, Y. Sakamoto, J. Hara, T. Komai, and T. Ooiwa (Japan)


Natural attenuation, Tetrachloroethylene (PCE), Tri chloroethylene (TCE); cis1,2dichloroethylene (cDCE), Heavy metal


The degradation behavior of chlorinated solvents were difference between each sites and classified in three types; (A) degradation with by-products, (B) degradation without by products, (C) non-degradation. The chemical components in the groundwater of the degradation type (A) showed lower redox potential (ORP), dissolved oxygen (DO) and higher heavy metals such as iron and manganese. These anaerobic reducing ambient is suitable for the bacteria concerned with the reductive dechlorination. Further, there is a possibility that chlorinated solvents are dechlorinated by catalysis, for example pyrite, containing within the soil. The chemical components in groundwater showed higher ORP, DO (degradation type (B)). Since the contaminant at the site YO was PCE which was not degraded by aerobic microorganisms, the reason for the natural attenuation might be dispersion or dilution. Although the higher ORP, DO were detected at degradation type (C), the VOC (TCE) was not attenuated at the site HK. This suggest that the dense non-aqueous phase liquids (DNAPLs) exist in the soil or groundwater, or the biochemical activity is low in this condition due to lower temperature.

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