中文摘要：

设计天然细砂模拟实验,利用乳化植物油作为电子供体,研究生物地球化学作用对Cr（Ⅵ）的还原过程和机理.结果表明,乳化油可以使地下水呈弱酸性,反应体系p H值最终为6.59;并长期维持还原环境,Eh最终降低至-158.6m V.乳化油可显著促进土著微生物的异化铁还原作用,将细砂介质中的Fe（ⅡI）还原成Fe（Ⅱ）并耦合去除Cr（Ⅵ）.当反应进行到14d时,Cr（Ⅵ）全部被去除,反应第28d总铬完全被去除.Fe（Ⅱ）的累积对反应体系中的氧化还原环境有重要影响.当实验结束时,Fe（Ⅱ）浓度为44.40mg/L,乳化油消耗了48.9%.XPS和XRD表征分析反应后的细砂,结果表明生成的Cr（ⅡI）最终以Fe-Cr无定型态沉淀存在.

英文摘要：

Natural fine sands was used as simulated aquifer media and emulsified vegetable oil as electron donor in the experiments to investigate the process and mechanisms of the biogeochemical reduction of hexavalent chromium. The experimental results showed that the emulsified vegetable oil caused a slightly pH drop, and the final pH reached 6.59; a reductive condition could be maintained for a long term, and the final Eh declined to -158.6mV. Emulsified vegetable oil could accelerate the dissimilatory iron reduction process of intrinsic microorganism; the ferric in fine sand would be reduced to ferrous and hexavalent chromium removal coupled. The hexavalent chromium and total chromium was removed absolutely within 14 and 28 days, respectively. The accumulation of Fe （II） exert profound influence on the redox condition of the reaction system. The final Fe （II） concentration was up to 44.40mg/L, and 48.9% of emulsified vegetable oil was consumed at the end of experiment. Structural characteristics analysis of sands was studied by X-ray diffractometer （XRD） and X-ray photoelectron spectra （XPS）; the results showed that the trivalent chromium existed as the amorphous formation of Fe-Cr coprecipitation.