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

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).