title: Dynamics of pesticide residues in the autumn Chinese cabbage (Brassica chinensis L.) grown in open fields.
abstract: Residues of the pesticides chlorpyrifos, dimethoate, cyhalothrin, cypermethrin, fenvalerate, deltamethrin and chlorothalonil in the autumn Chinese cabbage (Brassica chinensis L.) were studied using gas chromatography. The results indicated that the residues were dependent on the frequency and rate of pesticide application and on the weather conditions immediately following spraying. When the Chinese cabbages were treated once at normal rates, the half-lives of the seven pesticides in the vegetable were 4.7, 5.3, 2.9, 3.5, 5.4, 4.3 and 4.0 days respectively. Thus, based on the recommended preharvest intervals, the residual levels of all pesticides were within the national standards. When the Chinese cabbages were treated four times at maximal rates at 5 day intervals, the half-lives of chlorpyrifos, cypermethrin and chlorothalonil in the vegetable were 3.6, 2.9 and 5.9 days respectively, so that, based on the recommended preharvest intervals, the residual levels of chlorpyrifos and chlorothalonil exceeded the national standards for pollution-free vegetables, but the residual level of cypermethrin was within the national standard. Effects of rain on pesticide final residues in plants treated four times were more significant than in those treated once.
authors.affiliation: Department of Entomology, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
authors.forename: Zhi-Yong
authors.initials: ZY
authors.lastname: Zhang
authors.forename: Cun-Zheng
authors.initials: CZ
authors.lastname: Zhang
authors.forename: Xian-Jin
authors.initials: XJ
authors.lastname: Liu
authors.forename: Xiao-Yue
authors.initials: XY
authors.lastname: Hong
mesh_terms: D000383:Agriculture; D001937:Brassica / Q000469:parasitology; D002681:China; D009570:Nitriles / Q000032:analysis*; D009946:Organothiophosphorus Compounds / Q000032:analysis*; D010573:Pesticide Residues / Q000032:analysis*; D011722:Pyrethrins / Q000032:analysis*; D012015:Reference Standards
chemical_list: D009570:Nitriles; D009946:Organothiophosphorus Compounds; D010573:Pesticide Residues; D011722:Pyrethrins; C005806:tetrachloroisophthalonitrile