Ecotoxicity Assessment of the Water Extracts from Metal-Contaminated and Hydrocarbon-Contaminated Soils

Soil water extracts could help to quickly assess the potential hazard of contaminants in soil, groundwater, and surrounding receiving water. In this study, the adverse effects of water extracts obtained from soils contaminated by heavy metals (sites A and B) or hydrocarbons (sites C, D and E) were evaluated using wheat, pak choi, and zebrafish. The test results obtained with freeze-dried soil samples showed a good correlation with those obtained from fresh wet soil samples. Phytotoxicity level was found to be greater in samples obtained from the metal-contaminated site B as compared to those from site A, whereas the opposite was observed for the zebrafish embryo acute toxicity. The water-soluble fractions of petroleum hydrocarbons in soils from sites C and D pose ecological risks to the environment, even though the concentrations of total petroleum hydrocarbon were below the established screening value. The results obtained with our battery of biological assays could complement the ecological risk estimation of a complex mixture of contaminants in soils. Site-specific ecological risk assessment using chemical analytical data, screening values, and ecotoxicity testing with soil water extracts could serve as a screening approach to identify the impact of contaminated soils on the freshwater environment.