新型溴代苯酚类消毒副产物的氯化降解机制

New Bromated Phenolic Disinfection Byproducts:Mechanism of Their Decomposition During Chlorination

最近,13种新型极性卤代苯酚类消毒副产物在氯化消毒后的饮用水中被发现,它们按结构被分成4组,分别是二卤-4-羟基苯甲醛、二卤-4-羟基苯甲酸、二卤水杨酸和三卤苯酚.为研究它们在氯化消毒过程中的降解机制,选取了其中的4种全溴代种类,即3,5-二溴-4-羟基苯甲醛、3,5-二溴-4-羟基苯甲酸、3,5-二溴水杨酸以及2,4,6-三溴苯酚,利用UPLC/ESI-tq MS中的前体离子扫描,多反应监测和子离子扫描,鉴定了这几种消毒副产物在氯化消毒过程中的中间产物以及终产物,并根据这些中间产物和终产物与消毒时间的关系推测了其降解路径.结果表明,除了3,5-二溴水杨酸相对较稳定外,其余3种消毒副产物在氯化消毒过程中不稳定,通过取代、水解以及氧化等过程最终降解为卤乙酸等脂肪族小分子消毒副产物.在降解过程中有许多中间产物被检测并鉴定出来,其中包含一组具有五元环结构的新型消毒副产物(三卤代-羟基环戊烯二酮).

Recently,13 new phenolic halogenated disinfection by-products（ DBPs） have been reported in chlorinated drinking water and have been classified into four groups： dihalo-4-hydroxybenzaldehydes,dihalo-4-hydroxybenzoic acid,dihalo-salicylic acids,and trihalo-phenols. In this work,the four fully brominated species（ 3,5-dibromo-4-hydroxybenzoic acid,3,5-dibromosalicylic acid,2,4,6-tribromophenol,and 3,5-dibromo-4-hydroxybenzaldehyde） were selected as representatives,and the decomposition mechanism of these new DBPs during chlorination was studied with the aid of ultra performance liquid chromatography/electrospray ionization triple-quadrupole mass spectrometry（ precursor ion scan,multiple reaction monitoring,and product ion scan）. Except for 3,5-dibromosalicylic acid,the new DBPs were not stable and could be finally decomposed to haloacetic acids through multistep substitution,hydrolysis,and oxidation. Various decomposition intermediate DBPs were detected,including a new group of halogenated DBPs with cyclic structures（ trihalo-hydroxyl-cyclopetene-diones）.