Study On Degradation Dynamics And Residue Of Cyhalothrin In Yali Pear Fruit

The use of pesticides provides unquestionable benefits in increasing agricultural production. However, it has the drawback of pesticide residues which remain in fruit and vegetable constituting a potential risk to consumers.The problems of pesticide residue beyond criterion, not only restrict our fruit's export,but also threaten our health. Therefore, analyzing pesticide residue is very significant to reasonable using of pesticide, to people's health and to "non-public hazards fruit".In this paper,we researched the degradation dynamics of cyhalothrin in yali pear in different period,and the influence to pesticide residue by spraying different times,and the mainly residual position of pesticide in yali pear.As follows the main results:1 Studies on residual degradation dynamics of 2.5% cyhalothrin in yali pear fruit, sprayed in three different periods as the last ten days of April, the last ten days of May and the last ten days of August, were according to spraying once, sampling time after time. In three different periods, degradation equations of cyhalothrin were:the last ten days of April: C=0.1049e^-0.0549t(r=-0. 9747) , the half-life:T_1/2=12.62d;the last ten days of May: C=0.069e^-0.0644t(r=-0.9588) , the half-life T_1/2=10.76d;the last ten days of August: C=0.2191e^-0.3626t(r=-0.9929) , the half-life T_1/2=7.32d;Residual degradation dynamics of these three periods all accorded with C=C_oe^-kt, and all had high relativity, and in normal conditions, degradation was very fast. Cyhalothrin was easily degraded in environment.2 The residual degradation dynamics of 2.5% cyhalothrin in peel and pulp of yali pear, sprayed in the last ten days of May and the last ten days of August were:the peel of the last ten days of May: C=0.0933e^-0.0671t(r=-0.9500) , the half-life: T_1/2=10.33d;the peel of the last ten days of August: C=0.1507e^-0.1245t(r=-0.9675) , the half-life: T_1/2=5.57d;the pulp of the last ten days of May: C=0.0496e^-0.0643t(r=-0.9533) , the half-life: T_1/2=10.78d;the pulp of the last ten days of August:C=0.0686e^-0.1111t(r=-0.9928) , the half- life: T_1/2=6.24d;Residual degradation dynamics of these three periods all accorded with C=C_oe^-kt, and all had high relativity. At the first day of spraying pesticide,cyhalothrin had the highest residue and decreased later.3 After spraying pesticide, the residue order of cyhalothrin in different positions of yali pear was: peel >total fruit>pulp,and the residue in peel position was far over than pulp, pesticide mainly remained in peel position of yali pear, the pulp position remained relatively low. So after spraying cyhalothrin in yali pear, residue of peel position was the key factor which could accord with or not accord with maximum residual limit standard.4 The residue of 2.5% cyhalothrin sprayed one, two and three times in yali pear fruit were 0.004 00mg/kg,0.006 38mg/kg,00987mg/kg.The result showed that: the final residue in yali pear fruit was influenced by different spraying times of cyhalothrin. But whatever sprayed one,two or three times, the final residue in yali pear fruit was not higher than MRL.5 The final residue of cyhalothrin sprayed one, two and three times in yali pear fruit in the non-bagged yali pear were: 0.00400～0.02053mg/kg.The residue of cyhalothrin in the bagged yali pear was lower than the LOD. The result showed that it could reduce the final residue of cyhalothrin in yali pear fruit by bagging when the fruit was growing.