Degradation And Migration Dynamics Of Three Fungicides During Storage In Pear Fruit

The paper sampling from Dangshan and Hefei used for investigate the residualdistribution regularity of thiophanate-methyl、carbendazim and their metabolites 2-a minobenzimidazole、benzimidazole in pear fruit.Selecting systemic pesticides thiopha nate-methyl、carbendazim and protective pesticide chlorothalonil as the research objects,studied the effect of pesticide residue and degragation in Dangshan crisppear by different storage temperature、soaking concentration、adjuvants during storage period,and the pesticides removal efficiency in Dangshan crisp pear by different washing methods.The main results of the research are summarized as follows:(1)The maximum residue of thiophanate-methyl、carbendazim、2-aminobenzimi dazole in total pear were 7.267 mg/kg、2.731 mg/kg、0.088 mg/kg on November 2013,0.417 mg/kg、4.964 mg/kg、0.255 mg/kg on May 2014;The detection rate of thiophanate-methyl、carbendazim、2-aminobenzimidazole in total pear were 59%、83%、18% on November 2013,15%、85%、70% on May 2014.The pear sample are divide into pulp、total fruit、pericarp to determinate on May 2014.The result sho wed that the average residue and detection rate of thiophanate-methyl、carbendazim、2-aminobenzimidazole were meet: pulp<total fruit<pericarp.The content in pulp is significantly lower than the pericarp,thiophanate-methyl、carbendazim、2-aminobenz imidazole were mostly exsisted in pericarp.The samples have not found benzimidazole in two different period.(2)Under different storage temperature,the residue of thiophanate-methyl(sho wed by carbendazim)、carbendazim、2-aminobenzimidazole in pear pulp were ND~0.590 mg/kg、ND~1.646 mg/kg、ND~0.842 mg/kg,the pesticide residue has no o bvious regularity with sampling time and soaking concentration.The residue of thio phanate-methyl(showed by carbendazim)、carbendazim、2-aminobenzimidazole in pear pericarp were 5.476~25.370 mg/kg、5.135~35.078 mg/kg、2.485~24.516 mg/kg,the pesticide residue and soaking concentration emerge positive correlation regularity,the higher soaking concentration,the greater pesticide residue,in course of time pesticides gradually degrade.Compared ambient temperature storage with low temperature storage,the fomer was degradated faseter.During ambient temperature and low temperature storage,the metabolite 2-aminobenzimidazole has found in pear pericarp,the residues were 0.169~0.859mg/kg、0.182~0.847 mg/kg,has no obvious regularity with sampling time and soaking concentration;the metabolite 2-aminobenzimi dazole has no found in pear pulp;the metabolites benzimidazole and chlorothalonil-4-hydroxy have not found in pear both pulp and pericarp.(3)At different storage conditions,the residues and degragation of thiophanatemethyl(showed by carbendazim)、carbendazim and chlorothalonil in total fruit were in accorded with the first order kinetics.8 hours after soaking test,the residues of six thiophanate-methyl(showed by carbendazim)experimental groups were 2.465~6.135 mg/kg.By the condition of ambient temperature storage,the degradation of half-life were 30.39~46.82 d and 55d after soaking test degradation rate were 58.17%~77.25%.By the condition of low temperature storage,the degradation of half-life were 72.95~96.25 d and 145 d after soaking test degradation rate were 67.57%~81.28%.8 hours after soaking test,the residues of six carbendazim experimental groups were 3.251~7.093 mg/kg.By the condition of ambient temperature stor age,the degradation of half-life were 36.47~45.29 d and 55 d after soaking test degradation rate were 43.19%~59.90%.By the condition of low temperature storag e,the degradation of half-life were 74.52~99.00 d and 145 d after soaking test degradation rate were 70.34%~75.98%.8 hours after soaking test,the residues of three chlorothalonil experimental groups were 0.262~5.200 mg/kg.By the condition of ambient temperature storage,the degradation of half-life were 35.00~48.12 d a nd 55 d after soaking test degradation rate were 57.70%~84.69%.By the condition of low temperature storage,the degradation of half-life were 78.75~87.72 d and145 d after soaking test degradation rate were 69.45%~76.19%.The results indica ted that the residue and soaking concentration of thiophanatemethyl(showed by car bendazim)、carbendazim and chlorothalonil in total fruit emerge positive correlation regularity,the higher soaking concentration,the greater pesticide residue,in course of time pesticides gradually degrade.Compared ambient temperature with low temp erature storage,former residue degragation speed were faster.(4)During ambient temperature and low temperature storage,choose diluted 900times、diluted 750 times、diluted 1920 times experimental groups put in synerdist from thiophanate-methyl、carbendazim and chlorothalonil experimental groups.After put in synerdist,the residues of thiophanate-methyl(showed by carbendazim)、carbendazim and chlorothalonil significantly increased in pear pericarp and total fruit,were 1.5~3.7 times the original experimental groups.The increase of pesticides residue in pear pulp were not obvious.The metabolite 2-aminobenzimidazole has found in pear pericarp,compared with original experimental groups the difference of residues was not significant;The metabolite 2-aminobenzimidazole has no found in pear pulp.The metabolites benzimidazole and chlorothalonil-4-hydroxy have not found in pear both pulp and pericarp.The residues and degragation of thiophanate-methyl、carbendazim and chlorothalonil in total fruit were in accorded with the first order kinetics,the degradation of half-life and velocity compared with original experimental groups the difference of residues was not significant.(5)Recorded the rotting rate and dehydration rate of all thiophanate-methyl、car bendazim and chlorothalonil experimental groups during storage period.The results showed that the rotting rate and dehydration rate gradually increase in course of time.Compared ambient temperature with low temperature storage,former rotting rate and dehydration rate were significantly higher.(6)Select thiophanate-methyl diluted 150 times and diluted 900 times with synerdist experimental groups、carbendazim diluted 100 times and diluted 750 times with synerdist experimental groups 、chlorothalonil diluted 480 times and diluted 1920 times with synerdist experimental groups to do washing test.The results indicated t hat the residues of thiophanate-methyl(showed by carbendazim)、carbendazim、 chlorothalonil in Dangshan crisp Pear could be reduce by rinsing and detergent soaking washing,and residue removal rate were meet: thiophanate-methyl(showed by carbendazim)<carbendazim<chlorothalonil.The removal efficiency detergent soaking washing was better than rinsing soaking washing,and in addition to synerdist three pesticides were no obvious difference.