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模拟紫外光解和太阳光解水相典型苯二氮革类镇静催眠药物地西泮,对其去除效率、转化产物及毒性进行了研究.地西泮可以被紫外光(波长254 nm)有效去除,其紫外光解的光量子产率为(2.32±0.17)×10-3 mol/Einstein.地西泮对模拟太阳光解(波长300～400 nm)具有较强的稳定性,在光照90 min时间内无任何降解.采用高分辨飞行时间质谱监测到65个地西泮紫外光解产物,其中49个紫外光解产物在电喷雾离子化正模式下被检出,16个在负模式下被检出.根据产物鉴定的结果和光解反应的特性,地西泮在紫外光解作用下可能会发生8种途径的转化,反应机制主要包括羟基取代反应、水解反应、脱甲基反应、脱苯基反应、七元杂环开环反应以及环化反应.通过毒理学模型计算预测,生成的主要紫外光解产物对鱼、水蚤和绿藻等水生生物的毒性增加.“,”The photochemical transformation of diazepam,one of the most known benzodiazepines,has been conducted in aqueous solution to investigate the removal rate,identify the reaction products and evaluate their toxicity.Diazepam can be effectively removed by UV light photolysis at 254 nm,with the quantum yield of (2.32±0.17)× 10-3 mol/Einstein.Diazepam has been found to be relatively stable in 90 min simulated sunlight irradiation (300-400 nm).65 products were identified for UV photolysis of diazepam using a high-resolution accurate-mass Triple TOF system.Among them,49 products were identified in positive electrospray ionization mode,and 16 in the negative electrospray ionization mode.On the basis of the products identification and phototranformation behaviour,8 plausible reaction pathways were proposed for degradation of diazepam during UV photolysis process.Structural changes to the diazepam molecule included hydroxylation,hydrolyzation,N-demethylation,loss of phenyl group,benzodiazepine ring rearrangement and contraction.Toxicity evaluation using USEPA EPI SuiteTM software indicated that the toxicity of the main phototransformation products was increased than that of the parent compound diazepam.