Characteristics Of Residual Distribution,Transport And Transformation Of Lambda-cyhalothrin On Wheat And Cotton

Lambda-cyhalothrin is a pyrethroid insecticide that is highly effective against harmful insects,low-toxic to non-target organisms,and easy to be degraded.Lambda-cyhalothrin is mainly used to control aphids,cotton bollworms and cabbage worms in wide rang of crops such as wheat,cotton,and vegetables.However,frequent and excessive use of lambda-cyhalothrin increases its environmental risk to non-target organisms.Therefore,it is of great importance to reduce such risk and reasonably use the lambda-cyhalothrin,based on the residual distribution,migration and transformation characteristics in crops after application.The objective of this study is to explore residual original deposit,distribution,migration and transformation characteristics of lambda-cyhalothrin applied in cotton and wheat at different doses.The main results are as follows:1.Lambda-cyhalothrin was applied to wheat in Lujiang and Suzhou and cotton in Hefei at 0.6,0.8 and 1.0 times the recommended dose(cotton 30 g ai/ha,wheat 11.25 g ai/ha).The residual original deposits of lambda-cyhalothrin in the different spatial parts of wheat and cotton from two different sites was compared.The amounts of residual original deposits of lambda-cyhalothrin in wheat followed the order of wheat leaf >wheatear > wheat straw at both sites.The amounts of residual original deposits of lambda-cyhalothrin followed the order of tender leaf ≈ old leaf > cotton fruit.2.The spatial distribution of lambda-cyhalothrin on the different parts of wheat and cotton was analyzed by detecting their residues at three application doses.The spatial distribution and migration characteristics of the wheat from the two sites were consistent and followed the order of wheat leaf > wheatear > wheat straw,which had no significant difference between northern and southern districts with different climate conditions.The residual distribution of lambda-cyhalothrin followed the orders of wheat tender leaf > old leaf > cotton and tender leaf ≈ old leaf > cotton fruit after applications for 3 and 5 d,respectively.3.The dissipation half-lives of lambda-cyhalothrin in wheat were 2.65-4.75 d and 1.81-3.73 d in Lujiang and Suzhou,respectively,indicating that the degradation rate in Suzhou was slightly faster than that in Lujiang.The half-lives of lambda-cyhalothrin in the cotton was 3.21-5.54 d,suggesting that degradation rate of lambda-cyhalothrin in was generally slower than that in wheat.4.The metabolites of lambda-cyhalothrin after applications in wheat and cotton were detected using Gas Chromatography-Triple Quadrupole Mass Spectrometry and High Performance Liquid Chromatography.The metabolites 3-phenoxybenzyl alcohol(PBOH),3-phenoxybenzaldehyde(PBCHO)and 3-phenoxybenzoic acid(PBCOOH)was found to be in wheat and cotton after applications of lambda-cyhalothrin.