ORIGINAL ARTICLE Geophysical investigation using resistivity and GPR methods: a case study of a lubricant oil waste disposal area in the city of Ribeira ˜o Preto, Sa ˜o Paulo, Brazil Alexandre Lisboa Lago Vagner Roberto Elis Welitom Rodrigues Borges Giovanni Chaves Penner Received: 4 June 2008 / Accepted: 5 August 2008 / Published online: 26 August 2008 Ó Springer-Verlag 2008 Abstract Geophysics has been shown to be effective in identifying areas contaminated by waste disposal, contrib- uting to the greater efficiency of soundings programs and the installation of monitoring wells. In the study area, four trenches were constructed with a total volume of about 25,000 m 3 . They were almost totally filled with re-refined lubricating oil waste for approximately 25 years. No pro- tection liners were used in the bottoms and laterals of the disposal trenches. The purpose of this work is to evaluate the potential of the resistivity and ground penetrating radar (GPR) methods in characterizing the contamination of this lubricant oil waste disposal area in Ribeira ˜o Preto, SP, sit- uated on the geological domain of the basalt spills of the Serra Geral Formation and the sandstones of the Botucatu Formation. Geophysical results were shown in 2D profiles. The geophysical methods used enabled the identification of geophysical anomalies, which characterized the contami- nation produced by the trenches filled with lubricant oil waste. Conductive anomalies (smaller than 185 Xm) immediately below the trenches suggest the action of bac- teria in the hydrocarbons, as has been observed in several sites contaminated by hydrocarbons in previously reported cases in the literature. It was also possible to define the geometry of the trenches, as evidenced by the GPR method. Direct sampling (chemical analysis of the soil and the water in the monitoring well) confirmed the contamination. In the soil analysis, low concentrations of several polycyclic aromatic hydrocarbons (PAHs) were found, mainly naph- thalene and phenanthrene. In the water samples, an analysis verified contamination of the groundwater by lead (Pb). The geophysical methods used in the investigation provided an excellent tool for environmental characterization in this study of a lubricant oil waste disposal area, and could be applied in the study of similar areas. Keywords Applied geophysics Á Electrical methods Á GPR Á Lubricant oil Introduction In Brazil, until the 1970s, industrial and urban waste was directly disposed of in the soil, as it was believed that the soil was an unlimited receptor for disposable and noxious substances (CETESB 2001—Companhia de Tecnologia de Saneamento Ambiental). However, this capability was overestimated, causing irreparable damage to the environment. Ground contamination is of great concern because this is where most of the food required for human survival is A. L. Lago (&) CPRM, Servic ¸o Geolo ´gico do Brasil, Avenida Pasteur, 404/1114, Urca, Rio de Janeiro 22290-240, Brazil e-mail: alago@rj.cprm.gov.br V. R. Elis Instituto de Astronomia, Geofı ´sica e Cie ˆncias Atmosfe ´ricas da Universidade de Sa ˜o Paulo (IAG/USP), Rua do Mata ˜o, 1226, Cidade Universita ´ria, Sa ˜o Paulo 05508-090, Brazil e-mail: vagnelis@iag.usp.br W. R. Borges SIGEO, Soluc ¸o ˜es Integradas em Geotecnologias, Rua Engenheiro Jose ´ Amadei, 450, Sa ˜o Paulo 05565-060, Brazil e-mail: welitom@sigeo.srv.br G. C. Penner Instituto de Ensino Superior Cole ´gio Oswaldo Cruz (COC), Rua Abraa ˜o Issa Halack, 980, Ribeira ˆnia, Ribeira ˜o Preto, 13566-590, Brazil e-mail: giovannipenner@yahoocom.br 123 Environ Geol (2009) 58:407–417 DOI 10.1007/s00254-008-1511-x