某城市工业区浅层地下水CAHs污染特征

2000—2002年采用气相色谱法对某市工业区浅层地下水中氯代脂肪烃(CAHs)含量进行了分析,在综合分析CAH污染的原因和途径的基础上,着重探讨了CAH在地下水系统中的迁移转化规律。结果表明,地下水中CAH检出率48 15%~85 19%,检出值质量浓度为0 1~71 89μg/L,与美国“EPA”标准5μg/L 相比,三氯乙烯、四氯乙烯超标率分别为59 26%和25 93%,超标倍数分别可达14 38 和9 128;三氯乙烯(TCE)和四氯乙烯(PCE)是主要污染物,重现性好;CAH对地下水的污染与其本身的物理性质、包气带的结构和地下水动力条件等因素有关,防污性能差的工业区CAH容易污染地下水;CAH在砂土中的迟后因子R值很小,很容易在地下环境中迁移;地下水流场是决定CAH分布的一个重要因素,沿着地下水流向,CAH浓度呈逐渐降低的趋势;地下水动态变化是引起CAH呈现季节性变化的主要原因。

Characteristics of chlorinated aliphatic hydrocarbons transported to shallow groundwater in the industrial area of a city

The content of chlorinated aliphatic hydrocarbons (CAHs) in shallow groundwater collected in the industrial area of a city has been studied by gas chromatography from 2000 to 2002. Moreover, the synthetic analysis and the study of groundwater contamination from CAHs and the characteristics of CAHs movement in shallow groundwater system are discussed. The results show that the CAHs content in shallow groundwater ranges from 0.1 μg/L to 71.89 μg/L, and the frequency of occurrence ranges between 48.15% and 85.19%. The CAHs that threaten the groundwater quality are primarily the TCE and PCE, and their content is 14.38 times and 9.128 times higher than that of the EPA standard of the USA (5 μg/L), respectively. The ratio of the number of samples exceeding the standard to the number of total samples is 59.26% and 25.9%, respectively. Groundwater contaminated by CAHs is relevant to the physical property of CAHs, the construction of vadose zone, the hydraulic condition, etc. The vulnerability of the contamination of groundwater in the industrial area is high. The groundwater is easily contaminated by CAHs. Since the lag factor R of CAHs is very small, the CAHS can move very easily in the underground environment. The groundwater flow field is a determinant factor for the distribution of CAHs in groundwater. The content of CAHs in groundwater changes from high to low in the direction of flow. The change in the CAHs content has seasonal characteristics owing to the fluctuation of groundwater.