地球物理方法中的地电方法所获取的地下含水层视电阻率如何转换为地下水中污染物的浓度分布是有待解决的问题。本研究探索基于地下水流动与溶质运移数值模型构建映射关系的方法。从构建的多个已知污染物浓度场出发，通过Archie定律建立地电模型并对其进行地球物理正演模拟来代表野外观测到的电阻率数据，而后通过反演获得视电阻率反演数据分布，最后通过分析污染物浓度与视电阻率反演数据的统计特征来建立映射关系。结果显示地下水浓度场和电阻率之间的映射关系可通过不同的统计方法如线性拟合、多项式拟合来建立，但在不同的模型区域映射关系有所差异，表现出空间差异性。相比于直接采用Archie公式将视电阻率转化为浓度场的方法，线性拟合或多项式拟合所建立的映射关系在映射精度方面都具有明显优势。两者在多数情况中的应用效果类似，但在部分区域渗透系数较小（例如：渗透系数k=28m/d）的情况下，多项式拟合的映射关系应用效果优于线性拟合的映射关系。总体而言，本研究所构建的基于地下水模型的映射方式比直接采用Archie公式的方法更为精确，并且能获取更多的场域整体信息，可配合钻孔取样监测在地下水污染调查方面发挥作用。
Geophysical method is an important technique in groundwater contamination investigation. The geoelectrical method is capable of mapping both low and high resistivity and has been commonly used to explore concentration of contamination in groundwater. How to convert apparent resistivity of groundwater into concentration distribution of contamination in groundwater should be first considered carefully. Therefore, it is necessary to establish a relationship between electrical resistivity and contamination concentration for concentration estimation using geoelectrical information. We present a method for establishing this relationship based on groundwater numerical model. In this method, the relationship of electrical information and concentration information is obtained by comparing the contamination data from solute transport model with the electrical resistivity data from geophysical forward and inverse modeling. The results show that there is a clear relationship between the electrical resistivity and contamination concentration, which also has a spatial heterogeneity. The applications of the relationships established using linear fitting and polynomial fitting both are better than that by converting electrical resistivity data to concentration directly using Archie's law. In addition, the relationship established using polynomial fitting is better than that using linear fitting in some cases. The method proposed in this work has great potential for estimating the concentration of groundwater concentration based on geoeletrical data.
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