Soil ecotoxicology and mesofauna at the site of an attested oil spill in Ipanema National Forest

A disused electrical substation was the site of the spill of 40,000 L of Ascarel oil. However, none of the expected prin­cipal contaminants were chemically detected above established guidelines. Since the analysis of other possible contaminants is extremely expensive and impractical, the objective of this study was to indirectly evaluate possible contamination by determining the influence of physico-chemical parameters on the variation in soil mesofauna data and ecotoxicological testing. The tested substation is located in Ipanema National Forest in São Paulo State, Brazil. The area surrounding this site has several different soil uses and vegetation cover types. The square 200 m × 200 m collection area was defined by a grid comprised of 6 equally spaced lines along each axis. Soil samples were taken at each intersection save for 2, for a total of 34. Ecotoxicological testing was completed using Enchytraeus crypticus. The mesofauna was affected by multiple soil attributes that together accounted for 75.5 and 84.8% of the variability in samples taken from secondary forest and wooded pasture, respectively. However, variability in the E. crypticus testing was not strongly correlated to these physico-chemical attributes, possibly due to the tolerance of the tes­ted species to the variations observed in this study. This provides strong evidence that no contaminants are affecting local biota. However, additional studies are needed to analyze more complex abiotic factors that might account for the observed variability.