二甲四氯胺盐除草剂在稻田环境中的残留及消解动态

在湖南长沙、浙江杭州和贵州贵阳采用田间试验方法,研究了除草剂二甲四氯胺盐在水稻及稻田环境中的残留及消解动态。稻田水、土壤、植株用二氯甲烷和酸溶液混合提取,稻米采用甲醇和水混合提取,经HPLC测定。结果表明,二甲四氯胺盐在稻田水、土壤、鲜植株、糙米样品中的添加回收率均大于80%。在稻田水中二甲四氯胺盐的半衰期为5.75~6.76 d,土壤中二甲四氯胺盐半衰期为6.67~7.38 d,在水稻鲜植株中二甲四氯胺盐半衰期为5.50~6.68 d,降解较快。收获的水稻糙米中二甲四氯胺盐的残留量均未检出。二甲四氯胺盐在糙米中最高残留限量(MRL值)推荐值为0.1 mg/kg。建议75%二甲四氯胺盐水剂的使用剂量为600 g/hm2,施药1次,在正常收获期收获水稻是安全的。

Field Experiments on Residues and Degradation of MCPA Dimethylamine Salt in Paddy Fields

This paper reports the field experiments conducted in paddy fields of Changsha,Hangzhou and Guiyang with the purpose of investigating MCPA dimethylamine salt regarding its residues in the environment including soil,water and plant and its degradation in environment.Sampling and analysis were described with the stress emphasis on chemical analysis involving extraction and determination by use of HPLC.The analytic results showed that in general fortified recoveries of MCPA dimethylamine salt in water,soil and plant(incl.seedling and brown rice) were more than 80% and its residue in brown rice was not detectable.As to its degradation in water,soil and plant,determination of half-life was involved,which indicated that it degraded relatively fast in rice seedling.In addition,the author recommended that the maximum residue limit(MRL) of MCPA dimethylamine salt contained in brown rice be 0.1 mg/kg.To safeguard the residue in the rice under the MRL,it was suggested that the application to paddy field should be only once and in addition,the dose of MCPA dimethylamine salt applied be 600 g/hm2 with an aqueous solution concentration of 75%.