Evolution of Fluid Electrical Conductivity Profiles Associated with a Saline Contaminant Plume in a Horizontal Single-Plane Fractured-Rock Aquifer System

Abstract

Fluid electrical conductivity (FEC) profiling is a simple and efficient technique used to identify groundwater flow zones intersected by a borehole. These zones can be targeted for groundwater sampling, conducting tracer tests, and determining hydraulic properties of aquifers. While the method has been used for decades and will probably continue to be used, its application has not yet been studied in a controlled aquifer environment in order to understand the typical FEC profile responses in aquifers of different structures and groundwater qualities. This information would assist in the interpretation of borehole FEC profiles in different hydrogeological and hydrogeochemical conditions. The primary aim of this study is to investigate the behavior of FEC profile responses associated with a saline contaminant plume in a horizontal single-plane fractured-rock aquifer system. Laboratory and field tests were utilized to achieve this aim. Two distinct FEC profiles were observed; these are described and conceptualized as the background FEC profile associated with natural water quality flow conditions and the plume-peak FEC profile associated with a saline contaminant plume. These conceptual FEC profiles can be used as basis for assessing the evolution of saline contaminants in aquifers of similar conditions and as guide for collecting groundwater samples and understanding the meaning of the data derived from such samples. Furthermore, the findings of this study provide new insight into the nature of FEC profile characteristics associated with a saline contaminant plume in a horizontal single-plane fractured-rock aquifer system.