Detection of three-dimensional transport processes in porous aquifers using geoelectrical process quotient tomography

摘要

The increase in activities in hydrogeology offers a promising field for the application of geoelectrical methods to investigate contamination plumes and groundwater migration. This paper presents a monitoring technology for salt tracer injection into shallow aquifers using geoelectrical measurements. A new approximate inverse mapping algorithm called Process Quotient Tomography technique (PQT) is being used to interpret the relative change between pre-injection and post-injection resistivity values in one inversion procedure. The properties and quality of this new three-dimensional imaging procedure are demonstrated by a salt tracer injection experiment in conjunction with surface resistivity measurements. Two essential effects are observed, a fast tracer flow and a slow diffusion of brine remains. A three-dimensional reconstruction of the salt water plume shows a flow-dependent horizontal and a density-related downward movement. The PQT results allow the estimation of direction and velocity of groundwater flow. Additionally, a diffusion effect generated by disturbances in the injection well environment is seen. The advantage of the PQT technique is the requirement of only one access point to the aquifer and the relatively inexpensive realization of data processing.