地下水污染风险评价中污染源荷载量化方法的对比分析

地下水污染风险评价是地下水资源保护和地下水污染防治区划的重要基础,其评价体系通常由污染源荷载、地下水脆弱性和地下水价值3个要素构成.由于污染源荷载量化方法的差异,必然存在对污染源基础信息的需求差异,以及对最终评价结果的影响未知等问题.为探讨污染源荷载量化方法对地下水污染风险评价的影响,本文选择具有代表性的评分指数法和定量指数法,以滹沱河冲洪积扇中尺度研究区为例,分别进行污染源荷载量化,耦合叠加相同的地下水脆弱性、地下水价值要素,进行地下水污染风险评价,并作对比分析.结果表明,两种方法得出的污染源荷载量化结果存在较大差异,风险评价的最终结果在风险数值特征及风险级别的空间分布上差异也比较显著,说明污染源荷载量化方法的选择对风险评价结果有重要影响;评分指数法适用于基础信息精度较低的大尺度评价区,方法简单,评价结果可靠性程度略低,定量指数法适用于基础信息精度高的中小尺度评价区,方法略复杂,但评价结果可靠性更高,反映出评价区的尺度效应对方法的选择有重要影响.

Comparison and Analysis of the Quantitative Methods for Pollutant Sources Load in Groundwater Contamination Risk Assessment

Groundwater contamination risk assessment is an important basis for the protection of groundwater resources and the prevention and control of groundwater pollution. Its evaluation system is usually composed of three elements, which is vulnerability, pollutant source load and groundwater value. The pollutant source load plays an important role in risk assessment. Because of the difference among methods for pollutant sources load quantification, there will inevitably be different demand for the basic information survey on pollutant sources, as well as unknown impact on the final assessment results. In order to explore the impact of quantitative methods for pollutant sources load on groundwater contamination risk assessment, a case study was conducted in the mesoscale region of alluvial fan in Hutuo River, China. The two representative methods of grading index and quantitative index assessment systems were applied to quantify the pollutant sources load, in combination with the same vulnerability and groundwater value. The results constructed from different risk assessment systems were compared. The results showed that there were great differences between the two methods of quantification for pollutant sources load, and the result of contamination risk assessment also revealed significant differences in the feature of risk valve and the spatial distribution of the risk levels. The results of contamination risk assessment were strongly influenced by the choice of quantification for pollutant sources load methods. The grading index method was suitable for large scale region with lower precision of basic information and was simple, and the results of assessment had relatively lower reliability. The quantitative index method was suitable for the mesoscale and micro-scale region with higher precision of basic information and was relatively complicated, and the results of assessment had relatively higher reliability. It was shown that the scale effect of evaluation region had an important influence on the choice of methods.