The Ecotoxicity Of Pyrethroids On Earthworm(eisenia Fetida)in Soil

Eight pyrethoid residues in the greenhouse vegetable soils of four vegetable bases around Shenyang were analyzed with the method of the ultrasonic-assisted extraction,silicagel column purification and gas chromatography detection. As the same time, the toxicity of three typical pyrethroid pesticides(cyfluthrin, deltamethrin and bifenthrin)was discussed through their effects of acute toxicity, reproductive toxicity and molecular ecotoxicity on the earthworm Eisenia fetida. According these ecotoxicity test results, the most suitable index was filtrated for the early diagnosis of pyrethroidcontaminated soil.The study of pyrethoid residues of four vegetable bases in Shenyang indicated that the detection rate of the pesticide was high and multiple pesticides were detected. The average level of deltamethrin was the highest with 23.5 μg·kg-1 in soil by dry weight. In total, the residual level of total pyrethoid pesticides in soil of the vegetable bases was low, which belongs to the low residue level. Compared with the open fields, the detection rate and the residual concentration of pyrethoid pesticides in soils were relatively higher in the greenhouse vegetable field. The pesticide residues were found mainly in the 0-20 cm soil layer, and there were no significant differences in the different soil layer from 20 cm to 100 cm. Soil physico-chemical properties including pH, organic matter content, TN and TP had no significant effects on the residual pyrethroid concentrations(p>0.05).Acute toxicity test indicated that the toxicity of the three pyrethroid being in an order of cyfluthrin > deltamethrin > bifenthrin in filter paper test and soil test. The acute response text showed that 48hLC50 of cyfluthrin, deltamethrin and bifenthrin by the filter paper contacting method were 16.17 μg·cm-2、3637.84 μg·cm-2 and 485.78 μg·cm-2, respectively, and the 14dLC50 of cyfluthrin, deltamethrin and bifenthrin by the soil incubation method were 134.7 mg·kg-1、196.6 mg·kg-1and 3440.9 mg·kg-1, respectively.The study of growth and reproduction toxicity of pyrethroid on earthworms indicated that cyfluthrin inhibited the growth of earthworms, and deltamethrin and bifenthrin induced the growth of the earthworm but this effect was slow. In the whole experiment, cyfluthrin induced cocoon production in short-term and inhibited cocoon production in long-term, but restrained the incubation of juveniles. Low dose deltamethrin induced while high dose restrained the cocoon production. Deltamethrin showed double effects to the incubation of juveniles, that was, short-term induction and long-term inhibition, and low-concentration(0.5-10 mg·kg-1) induction and highconcentration(25-50 mg·kg-1) inhibition. Bifenthrin induced the cocoon production and incubation of juveniles. The toxicity of the three pyrethroid showed the decreasing order of cyfluthrin > deltamethrin > bifenthrin.The significant inverse U type dose-response relationship was observed between the CYP3A4 activity and the concentrations of pyrethroid. This experiment demonstrated that CYP3A4 can be used as a potential biomarker to assess the ecological risk of pyrethroid pollution in soil. The induced concentration of the three pyrethroids on CYP3A4 in the short-term demonstrated that the toxicity sequence was cyfluthrin >deltamethrin > bifenthrin.The low toxicity of pyrethroids on the earthworm were revealed by the LC50,growth rate and cocoon production rate, with the sensitivity being in an order of enzyme activity toxicity > growth and reproduction toxicity > acute toxicity.