[Soil-based eco-toxicity of petroleum to terrestrial higher plant after phytoremediation].

ABSTRACT

Petroleum-contaminated soil after five-year phytoremediation was taken as tested soil initially spiked with a serial diesel concentration of 5 000, 15 000 and 30 000 mg/kg (dry weight). Residual concentrations of mineral oil by chemical analysis of gravimetry, as well as the soil-based eco-toxicity to wheat (Triticum aestivum L.), the terrestrial higher plant by several ecotoxicological bioassays including seed germination and root elongation test, early seedling growth test, contents of cytochrome P450 monooxygenases, activities of antioxidant enzymes (superoxide dismutase, SOD, and peroxidase, POD), and lipid peroxide (malondialdehyde, MDA content in wheat seedling leaves, etc. were evaluated. Results showed that mineral oil was well removed in each treatment by chemical analysis, with residual concentrations ranging from 199 to 877 mg/kg (dry weight) and with total removal rates between 90.1% and 97.2%. The evaluating results by eco-toxicological assays differed to some extent from those by chemical analysis, meanwhile, eco-toxicity of each treatment differed depending on endpoints by different bioassays. Among the ecotoxicological indexes, root length (48 h), root fresh weight (7 d), contents of P450, activities of SOD, and contents of MDA, etc. exhibited better indication to the soil toxicity. The general evaluation by combining the two analyses chemical and eco-toxicological indicated that the ecological risk was higher in most intermediately- and heavily-contaminated treatments (initially spiked with diesel concentration of 15,000 mg/kg and 30,000 mg/kg).