喹硫磷在茶叶中的残留降解

在杭州和长沙两地两年用不同剂量、不同施药方法进行的研究表明,喹硫磷在茶树鲜叶上降解速度中等,1天后的降解率平均7.15％,降解速度低于辛硫磷、马拉硫磷、敌敌畏等农药。用25％乳剂800倍液喷施后5天鲜叶中残留量低于10ppm,10天后低于1ppm,降解速率常数(K)0.47±0.06天,半衰期1.37±0.02天。降雨对喹硫磷在茶树上的降解有一定影响,尤其在施药后的近期。对成茶中在喷后不同间隔天数的残留量、含喹硫磷残留的鲜叶在加工过程中的降解率、成茶中喹硫磷残留量在泡茶时的浸出率,均进行了测定,并讨论了喷后不同间隔期鲜叶上的残留量和茶尺蠖幼虫致死剂量间的关系。建议喹硫磷在成茶中允许残留标准暂订为0.2ppm,茶叶喷施25％乳油800倍液后的安全间隔期为8—10天。

DEGRADATIVE DYNAMICS OF QUINALPHOS ON TEA SHOOTS

Results from laboratory and field experiments carried out in Zhejiang and Hunan provinces from 1981-1983 showed that quinalphos was degraded moderately on tea shoots and about 71.5% was degraded one day after application, being slower than the degradative rate of phoxim, malathion, finitrothion, dichlorvos and dimethoate. When used at 38.6-61.7g. a. i. per mu (25% EC 800-1000 dilutions), the quinalphos residue in fresh tea leaves was less than 10 ppm in the 5th day after application, and less than 1 ppm in the 10th day after application. The degradative rate constant (K) was 0.478±0.06 day^-1, the halflife (HL₅₀) was 1.37±0.02 days. Rainfall played a certain degree of influences on the degradation, especially within few days after application. The residue of quinalphos in the processed tea was generally less than 5 ppm in the 5th day after application, and less than 0.2 ppm in the 8-10th day after application. The oxygen analog of quinalphos was detected only in the fresh leaves and processed tea sampled in the 0-3 days after application (0.06-2.10 ppm), and was not detected afterwards. The degradative rate of quinalphos residue in the fresh tea leaves during the manufacturing process was averaged 65%.The quinalphos residue extracted from the processed tea with infusion procedure was averaged 12.4%.Based on the degradative studies and the determination of toxicity on insects, the relationship between the residual level on the fresh tea leaves in the different days after application and the lethal dose for the tea looper (Ectropis obliqua Warren) larvae was discussed. Besides, the authors proposed the maximum residue limit of quinalphos in processed tea to be 0.2 ppm,and the safety interval should be 8-10days after the use of 1:800-1000 dilutions of 25% EC quinalphos.