Abstract: 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.

Key words: groundwater contamination, concentration, electrical resistivity, groundwater numerical simulation