Abiotic Degradation of lodosulfuron-methyl-ester in Aqueous Solution

摘要

The abiotic degradation of iodosulfuron-methyl-ester was investigated under both alkaline and acidic pH conditions in the dark,and results showed it to be a rather stable molecule in neutral or slightly alkaline environments.Photochemical reactions were studied using a high-pressure mercury arc lamp,and results showed that direct phototransformation is possible under normal environmental conditions(lambda > 290 nm).High-performance liquid chromatography(HPLC-UV and HPLC-MS)analyses were used to identify the degradates and to study the kinetics of photodecomposition and hydrolysis.Five main products of iodosulfuron-methyl-ester degradation were tentatively identified,and one of them(4-methoxy-6-methyl-1,3,5-triazin-2-amine)was confirmed using an authentic standard.Among the phototransformation mechanisms,photosubstitution of the iodide atom by a hydroxyl group,photodissociation of the N-S bond,and photoassisted hydrolysis were observed.The quantum efficiencies(multiwavelength quantum yield)of the photodegradation under different conditions were determined,and values of 0.054(+-)0.02(pH 9.6),0.08(+-)0.02(pH 7),and 0.044(+-)0.008(pH 5.3)were obtained.