In-situ Remediation of Contaminated Soil with Chlorinated Organic Compounds using Natural Activity

本研究的目的是开发一种有效的利用天然矿物和微生物脱氯反应的有机氯污染土壤修复系统。主要研究成果如下：1. TCE与黄铁矿的脱氯反应在好氧条件下比在厌氧条件下进行得更好。三氯乙烯通过有机酸转化为二氧化碳和氯离子。黄铁矿被氧化并转化为硫酸根和铁离子。该反应的反应速率依赖于氧气浓度.硫化亚铁、黄铜矿等硫化物矿物对三氯乙烯的脱氯反应在厌氧条件下进行。实验中黄铁矿的反应速率最大.从硫酸盐还原环境中获得的厌氧微生物菌群可将三氯乙烯完全脱氯为乙烷。研究发现，对产甲烷菌的控制是该菌群降解三氯乙烯的重要因素.收集和分析了几个污染场地地下水中氯代有机化合物衰减的长期数据。通过分析，揭示了影响衰减的主要因素.采用土壤颗粒吸附、地下水扩散、微生物和矿物反应分解的迁移模型预测了TCE等氯代有机物在污染场地中的行为.初步设计了氯代有机物污染土壤的修复工艺。该组合工艺包括黄铁矿与污染土壤的混合和微生物群落中降解菌的活化.在好氧和厌氧条件下，黄铁矿对氯苯等氯代芳香族化合物也有一定的降解作用。这些结果表明，在水溶液中黄铁矿对二恶英及其衍生物有分解作用。

The purpose of this study was to develop remediation system for contaminated soils with chlorinated organic compounds using effectively with dechlorination reactions with natural minerals and microorganisms. Main research results are as follows.1. Dechlorination reaction of TCE with pyrite progressed well in aerobic condition rather than in anaerobic condition. TCE was converted to carbon dioxide and chlorine ion via organic acids. Pyrite was oxidized and converted to sulfate and iron ion. Reaction rate of this reaction depended on the oxygen concentration.2. TCE dechlorination with sulfide minerals such as iron sulfide, chalcopyrite and so on progressed in anaerobic condition. Pyrite gave maximum reaction rate in the experiment.3. TCE was completely dechlorinated to ethane by anaerobic microbial consortium obtained from sulfate reducing environment. It was found that control of methane producing bacteria was important factor for the TCE decomposition by this consortium.4. Long-term data for the attenuation of chlorinated organic compounds in groundwater in several contaminated sites were collected and analyzed. Main factor of the attenuation was revealed by the analysis.5. Behavior of chlorinated organic compounds such as TCE in the contaminated site was predicted using transport model containing adsorption to soil particles, diffusion in groundwater and decomposition with microbial and mineralogical reaction of the compounds.6. From these results, soil remediation process contaminated with chlorinated organic compounds was basically designed. The combined process consists of mixing of pyrite with the contaminated soil and activation of degrading bacteria in the microbial community.7. Chlorinated aromatic compounds such as chlorobenzenes were also decomposed by pyrite in aerobic and anaerobic systems. These results indicate the possibility of decomposition of dioxins and their derivatives by pyrite in aqueous system.