基于折减系数的地下水污染风险评价方法探究

Study on groundwater contamination risk assessment method based on reduced coefficient

地下水污染风险评价对地下水污染防治与地下水合理开发利用具有重要意义.目前国内外最常用的是基于DRASTIC模型结合污染荷载的地下水污染风险评价方法.本文对比总结了国内外地下水污染风险评价方法体系,针对目前方法体系的不足,提出基于折减系数的评价体系,通过引进"折减系数"来表征污染物在包气带中的迁移转化过程,最后以石家庄滹沱河冲洪积扇平原区为例进行了地下水污染风险评价.结果表明,研究区污染风险最高的地区多为工业区;其次是滹沱河河道及周边地区地下水污染风险较高,原因主要是该地区包气带基本以砂性土为主,且排污河污染物随河水常年下渗;农业污染源排放量较小,农田区污染风险最低.该方法体系实现了污染物由地表到达地下的衰减过程量化,且简便易操作.此外,该方法把污染物毒性与污染物到达地下水面的量放在同一层次,使得地下水污染风险评价的结果更具说服力.

Groundwater contamination risk assessment plays an important role in its pollution control and rational utilization. At present the most commonly used assessment method is to combine the DRASTIC-based intrinsic vulnerability assessment with the contamination load. In this paper, several groundwater contamination risk assessment systems were compared and summarized. In order to characterize the transport and transformation of contaminants in vadose zone, reduced coefficient was introduced in the current assessment system. A case study by using this method has been carried out in Shijiazhuang Plain of alluvial-proluvial fan of Hutuo River. The assessment results indicate that the regions with the highest contamination risk are mostly industrial districts. The Hutuo River and its surrounding area show relatively high risk, because most of the soil layers in unsaturated zone of the study area are sandy soil and pollutants in the polluted river infiltrate with the river water throughout the year. Farmland area has the lowest contamination risk because of the low agricultural pollution emission. The system has realized the goal of quantifying the process of contaminants going through the vadose zone in an effective and operational way. In addition, the toxicity of a pollutant and the quantity when it reaches groundwater were considered in a same level, which makes the results of risk assessment more persuasive.