某四氯化碳污染场地自然恢复的地球化学特征

Geochemical Characteristics of Natural Attenuation in a Carbon Tetrachloride Contaminated Site

为了给某四氯化碳污染场地修复设计提供理论基础,在场地监测采样的基础上结合地球化学还原脱氯作用的反应过程,筛选了硫酸盐、二价铁、氯化物、三氯甲烷、碳酸氢盐作为标志性组分,开展了场地自然恢复的地球化学特征分析,划分对比了污染羽中部内外两区域各指标的质量浓度差异,结果显示:污染羽中部范围内标志性组分间具有明显的空间相关性,即反应物硫酸盐质量浓度明显降低,伴随了生成物二价铁所占比例的明显升高和降解产物氯离子与三氯甲烷质量浓度的升高,且显示了碳酸氢盐质量浓度的减少;上述指标之间的关系说明了四氯化碳脱氯作用的发生。本次地球化学特征分析显示出该污染场地具有较强的自然恢复潜势。

In order to provide a theoretical basis for the treatment design of a carbon tetrachloride(CT)contaminated site in the northern China,based on the sampling work and the geochemical reductive dechlorination process,we selected sulfate,ferrous iron,chloridion,trichloromethane,and bicarbonate as the target components,and compared the differences of the mass concentration between the selected components in the central and the outer part of the CT plume to analyze the geochemical characteristics of natural restoration of the site.The results show that there is a clear spatial correlation among the aforementioned components in the central part of the pollution plume.That is,the mass concentration of the reactant sulfate decreased obviously with the significant increases of the proportion of the product's divalent iron and the concentration of the degradation product chloride ion and chloroform correspondingly.Chloridion and trichloromethane,as dechlorination products,rise considerably with the decrease of bicarbonate.The relationship described above indicates the occurrence of the degradation of CT.The analysis of geochemical characteristics demonstrates that the site has an appreciable natural attenuation potential.