Integration of geoelectrical methods in the diagnostic of a diesel contaminated site in Santa Ernestina (SP)

Abstract

Hydrocarbons meet more than 50% of world wide demand for industries and main transportation means. Unfortunately, the use of this energetic matrix in large scale is the frequent cause of contamination of soil and groundwater, scenarios that present risks to human health and limit the use of natural resources. Geophysical methods constitute an important tool for the evaluation of these cases, as they offer important information in an indirect and comprehensive manner, with low relative cost, guiding remediation efforts in contaminated areas. In this work a geophysical study was performed in Electro DC Resistivity and Induced Polarization in a sandy tropical soil contaminated by a 58.000L diesel spillin a railway accident, and aimed to diagnose the contamination scenario after more than seven years from the incident. 11 lines of electrical imaging were performed with generation of resistivity and charge ability models integrated in 3D view blocks. The results indicated the punctual occurrence of shallow zones of low resistivity close to the place of contaminants infiltration, associated to the action of natural attenuation processes. The model presented zones of high chargeability associated to the probable presence of metallic minerals formed during and after the action of biodegradation processes. The results set pointed to a general scenario of an advanced stage of decontamination in the area, with effective natural attenuation processes.