Natural attenuation of diesel-oil contamination in a subantarctic soil (Crozet Island)

An accidental contamination occurred in subantarctic Crozet Island between July and November 1997 near the "Alfred Faure" scientific station (51°51'E-46°25'S). More than 20,000 l of diesel fuel was spilled in the soil in the vicinity of the power station. In order to evaluate the efficiency of the expected bioattenuation process, the contaminated area was sampled in December 1999 for bacterial and chemical analysis. All samples were analysed for total bacteria, heterotrophic viable assemblages and hydrocarbon-utilising microflora. The results of this first analytical survey clearly show a significant response of subantarctic microbial soil communities to the hydrocarbon contamination. Significant increases of total, heterotrophic and hydrocarbon-utilising micro-organisms occurred in the more contaminated zone (from less than 5᎒⁴ MPN g^-1 wet soil to more than 10⁸ MPN g^-1 wet soil for hydrocarbon-degrading micro-organisms). The very high numbers of hydrocarbon-degrading micro-organisms present in the more contaminated zone are clearly linked to early bioattenuation activities. Chemical results provided some clear indications that spilled fuel was still well preserved from chemical and biological weathering 1 year after the spill, as light aliphatics and aromatics were present in all oiled samples and little differences were usually observed between samples.