Acute Toxicity of Twenty-Two Commonly Used Herbicides to Earthworm (Eisenia fetida)
22种常用除草剂对蚯蚓(Eisenia fetida)的急性毒性

To evaluate the effects of pesticides on soil invertebrates,acute toxicities of twenty-two currently-used herbicides to the earthworm(Eisenia fetida) were determined by using filter paper contact test and artificial soil test.Results of 48-h filter paper contact test indicated that terbutryn,pretilachlor,S-metolachlor,acetochlor and anilofos were moderately toxic to E.fetida with LC50 values ranging from 10.32(8.310-12.23) to 34.69(29.16-43.99) μg·cm-2.Atrazine,tribenuron-methyl,dicamba and paraquat were low toxic with LC50 values ranging from 102.5(66.57-138.7) to 235.0(199.4-279.5) μg·cm-2.2,4-D sodium salt,glufosinate-ammonium,glyphosate and cyhalofop-butyl were also low toxic with even higher LC50 values ranging from 422.7(344.7-577.3) to 601.4(451.3-957.4) μg·cm-2.The other tested herbicides including fenoxaprop-p-ethyl,terbuthylazine,metsulfuron-methyl,sulfometuron-methyl,rimsulfuron,bensulfuron-methyl,fluoroglycofen-ethyl,pyraflufen-ethyl and trifluralin were relatively nontoxic to E.fetida with LC50 values > 1 258 μg·cm-2.In contrast,results of 14-d artificial soil test showed that terbuthylazine was the most toxic to E.fetida and its LC50 value was 74.15(49.35-92.28) mg·kg-1.Dicamba,paraquat,fluoroglycofen-ethyl,pyraflufen-ethyl and trifluralin exhibited the least toxicities to E.fetida with LC50 values > 800 mg·kg-1.The other sixteen herbicides exhibited the relatively low toxicities to E.fetida with LC50 values ranging from 106.6(83.90-123.0) to 516.2(367.4-1 015) mg·kg-1.According to the guidelines of environmental safety evaluation for chemical pesticides,22 herbicides tested using artificial soil test could be classified as low toxic grade to E.fetida under laboratory conditions.Results demonstrated that different classes of herbicides varied widely in their toxicities,and the different herbicides within the same chemical class also had different toxicities against E.fetida.Toxicities of herbicides to earthworms varied depending on the chemical structure of herbicides and the bioassay procedures.Diphenylethers and dinitroanilines were the least toxic among all tested herbicides in both bioassay systems.