Responses of Different Test Objects to Experimental Soil Contamination with Crude Oil

Responses to contamination of several soil types with crude oil were comparatively analyzed in organisms of different trophic groups. Samples of soddy podzolic, light gray, soddy calcareous, dark gray, and floodplain soils were supplemented with oil in concentration ranges of 1-5 and 100-300 g/kg and tested in the laboratory for the effect on heterotrophic soil bacteria and higher plants (Lepidium sativum, Triticum aestivum, Picea obovata, and Pinus sylvestris). In addition, water extracts from oil-contaminated soils were tested for the effect on Chlorella vulgaris and Daphnia magna. It was found that agricultural plants Lepidium sativum and Triticum aestivum were more tolerant of low-dose oil contamination (1-5 g/kg soil), compared to seedlings of the taiga tree species Picea obovata. The abundance of heterotrophic bacteria increased in soils treated with low oil concentrations (up to 5 g/kg) and decreased when oil concentration reached 100-300 g/kg soil. The entire range of tested oil concentrations caused reduction in the morphological diversity of heterotrophic soil bacteria. Experiments with water extracts from oil-contaminated soils showed that toxicity test with Daphnia magna was insufficiently sensitive and that the response of Chlorella vulgaris microalgae to soil contamination with oil was ambiguous. The floodplain soil proved to be most tolerant to oil contamination, while soddy calcareous and light gray soils were most vulnerable.