Environmental Characterization of an Industrially Contaminated Area by Tetrachloroethylene Using the Resistive-Capacitive Method.

Abstract

Investigation of soil and groundwater contamination is essential for assessing environmental risks and monitoring remediation processes. Geophysical methods effectively map and characterize subsurface properties without requiring direct excavations. These methods provide data on geological structure, lithological changes, groundwater level, contaminant identification, and remediation process monitoring. Being non-invasive, they offer an advantage over drilling operations by avoiding the need for soil excavation. This reduces the risk of contaminant migration during investigation activities. The study area in São Paulo corresponds to a former industrial galvanization site where contamination by chlorinated solvents, especially tetrachloroethylene, occurred. Remediation measures such as pumping and treatment, multiphase extraction, soil/waste removal, and chemical oxidation were implemented in the area. The contaminant and remediation processes alter the geophysical signatures of the environment, enabling the use of the electrical resistivity method. However, applying this method can be challenging in urban areas due to pavement and urban interferences. The resistive-capacitive method was employed, allowing continuous data acquisition over large areas without the need to insert electrodes into the soil. Additionally, traditional electrical profiling and induced polarization were used to gather data at greater depths. The integration of geophysical methods with soil sample descriptions in liners provided an analysis of subsurface characteristics and affected areas. Although challenges exist in applying it to urban areas due to pavement and interferences, the electrical resistivity method can contribute to the Conceptual Site Model by filling data gaps between wells and delineating the contaminant's influence area and the chemical oxidation remediation process.