| Cantharidin (C10H12O4, hexahydro-3α,7α-dimethyl-4β,7β-epoxyisobenzofuran-1, 3-dionc),consisted in meloid insects, is an important natural active ingredient.It has been widely applicated in medicine, and also been developed as a new type of biopesticide because of its high insecticidal activity. Based on the former research,1.0% cantharidin EC was developed by the Institution of Entomology, Northwest A&F University. This dissertation focused particularly on the studies of environmental safety evaluation of cantharidin and 1.0% cantharidin EC.1.The toxicity of cantharidin and 1.0% cantharidin EC against some of non-target organisms were determined according to "Experimental Guideline for Environmental Safety Evaluation of Chemical Pesticides".The result shows that the acute toxicity LD50 of 1.0% cantharidin EC against quails was 12.096 mg/Kg, and its toxic accumulation was low. The LC50 for contact toxicity and stomach poisoning activity against ladybugs were 114.724 mg/L and 48.007 mg/L respectively. The inhibition rate to breathe of soil microbes was lower than 50% when pure cantharidin or cantharidin EC were at a level of 100mg/Kg, and its power of cantharidin to the ammoniation and nitrification of soil microbes was not appearent. However, cantharidin of high concentration effects on the nitrogen fixition of soil microbes to some extent. The acute toxicity LC50 of cantharidin against fish were 7.992,4.790,3.401 and 2.440 mg/L at 24h,48h,72h and 96h after the treatments respectively. It was indicated that the cantharidin and 1.0% cantharidin EC had low toxicity against quails,ladybugs and soil microorganisms,but had a moderate toxicity against fish.2.The method for determining residues of cantharidin in water and soil by chromatography gas (GC) was established.The recovered rate of cntharidin in water and soil by GC were 81.72%～105.64% and 75.97%～88.34% respectively, which are both higher than 75% than the limitation of residue analysis(>75%).3.Adsorption of soils to cantharidin by oscillation balance method was tested. Cantharidin was mainly adsorbed by soil when the water-soil system was in balance.It was found that adsorption processes of cantharidin in three kinds of soil all fitted to Freundlich(R2>0.956)and with L-type adsorption isotherm.4.The degradation of cantharidin in different soil was studied.The result shows that the degradation rate of cantharidin was fast in both non-sterilized soil and sterilized soil,but which was faster in the later. The degradation half-life in non-sterilized black soil from Northeast china, Henan soil and Jiangxi soil were 0.722d,0.830d and 0.755d respectively, but 1.158d,1.751d and 1.444d in sterilized soil aforementioned respectively. According to the pesticide residues in soil classification of the two standards of Metealf and Environmental Protection Agency of People's Republic of China, cantharidin is one kind of low residua pesticide.5.Abiotic hydrolysis of cantharidin in sterile buffer solutions was studied. The half-lives of cantharidin in neutral (pH 7) and acidic (pH 5)water were 5.73d and 8.00d respectively, the half-life was 2.77d in pH 9 solutions.In conclusion,1.0% cantharidin EC had low toxicity against quails,ladybugs and soil microorganisms,but had a moderate toxicity against fish; Cantharidin is one type of weak motility pesticide, and it was mainly absorbed by soil in the soil-water system in balance and doesn't pollute the environment; Cantharidin degrades fast in soil and water, and it is lower persistent in environmental media. |
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