湘南地区烟叶中高效氯氟氰菊酯和氯氰菊酯的降解动态研究

Degradation Dynamic of λ-Cyhalothrin and Cypermethrin in Tobacco Leaves in Southern Hunan

高效氯氟氰菊酯和氯氰菊酯是近年湘南地区烟叶中容易超标的拟除虫菊酯类杀虫剂。为了确保烟叶中高效氯氟氰菊酯和氯氰菊酯残留量不超过中国烟草总公司企业标准YQ 50—2014的限量值(1 mg/kg),试验考察了不同施药量条件下田间生长的鲜烟叶、烘烤时烟叶和室温储存的烤后烟叶的农药降解规律。结果表明:高效氯氟氰菊酯和氯氰菊酯在田间鲜烟叶中的降解动态与一级动力学方程匹配度较高,半衰期分别为8.1~9.2 d和8.7~11.1 d;烟叶烘烤时的加工因子分别为0.77~0.88和0.67~0.89;室温储存的烤后烟叶的高效氯氟氰菊酯和氯氰菊酯的降解速度较慢,其半衰期在102~377 d。综合考虑烤后烟叶农药残留量和加工因子,建议:高效氯氟氰菊酯的施药量不宜超过1倍推荐用药量,采摘间隔期为23 d,氯氰菊酯的施药量不宜超过2倍推荐用药量,采摘间隔期为11 d。

Residues of cypermethrin and λ-cyhalothrin (pyrethroid insecticide) in tobacco are easy to exceed the standard in Southern Hunan in recent years.To ensure the pesticide residues in tobacco leaves not exceed the limited value (1 mg/kg) of the enterprise standard YQ 50—2014 of China National Tobacco Corporation,the degradation of pesticides in fresh tobacco leaves,tobacco leaves during curing and cured tobacco leaves stored at room temperature was investigated.The results showed that the degradation dynamics of λ-cyhalothrin and cypermethrin in field fresh tobacco leaves matched well with the first-order kinetic equation,with half-lives of 8.1-9.2 d and 8.7-11.1 d,respectively.The processing factors during tobacco curing were 0.77-0.88 and 0.67-0.89,respectively.The degradation rate of λ-cyhalothrin and cypermethrin in cured tobacco leaves stored at room temperature was slow,and their half-lives ranged from 102 d to 377 d.Considering the pesticide residues and processing factors of cured tobacco leaves,it is suggested that the dosage of λ-cyhalothrin should not exceed 1 times the recommended dosage,and T value of picking interval was 23 d,while the dosage of cypermethrin should not exceed 2 times the recommended dosage,and T value of picking interval was 11 d.