Ecotoxicity monitoring of hydrocarbon-contaminated soil during bioremediation: a case study

The ecotoxicity of hydrocarbon-contaminated soil originating from a brownfield site was evaluated during a 17-month biodegradation pilot test. The initial concentration of total petroleum hydrocarbons (TPHs) in the soil was 6380 microg/g dry weight. An amount of 200 kg soil was inoculated with 1.5 L of the bacterial preparation GEM-100 containing Pseudomonas sp. and Acinetobacter sp. strains (5.3 x 10(10) CFU.mL(-1)) adapted to diesel fuel. The concentration of TPHs in the soil decreased by 65.5% after bioremediation. Different organisms such as the bacterium Vibrio fischeri, terrestrial plants Sinapis alba, Lactuca sativa, and Hordeum vulgare, the water plant Lemna minor, the earthworm Eisenia fetida, and the crustacean Heterocypris incongruens were used for ecotoxicity evaluation. The highest toxicity was detected in the first period of bioremediation. However, certain toxic effects were detectable during the whole bioremediation process. The contact tests with plants, earthworms, and crustaceans were the most sensitive of all of the bioassays. Therefore, the contact tests performed directly on soil samples were shown to be a better tool for ecotoxicity evaluation of hydrocarbon-contaminated soil than the tests performed on soil elutriates. The ecotoxicity measured by the responses of the tests did not always correlate with the decrease in TPH concentrations in the soil during bioremediation.