• ClO • and BrO • are selective and only react with electron-rich compounds. • The reactivities of AABs to ClO • and BrO • are more pH-sensitive than that to HO • . • Basic pH could enhance the degradation of most AABs in light/chlorine systems. • The CP values of ClO • are much higher at pH 8 than pH 6 for removal of two AABs. • The rising dose of Br - can elevate the CP values of BrO • . The solar/chlorine and UV/chlorine systems as emerging advanced oxidation technologies (AOTs) are used for degrading trace organic contaminants (TrOCs) through generating various radical species. The pH is a vital parameter that significantly affects the degradation efficiency of contaminants. In this study, six aromatic acids and bases (AABs) are selected to investigate the pH-dependent degradation mechanisms and kinetics by two newly-discovered radicals (ClO • and BrO • ). Among the 16 dissociation species, the structures with electron-rich rings possess stronger reactivities to ClO • and BrO • than those with electron-poor rings, which is similar to the result of HO • . However, ClO • and BrO • are considered to be more selective and pH-sensitive reacting with AABs than HO • based on the corresponding second-order rate constants (M −1 s −1 ). Compared with acidic pH, the basic pH could improve the degradation rate of most aromatics in both systems. As pH increases from 6 to 8, the contribution percentages of ClO • in terms of the removal of the aromatics (except for benzoic acid) in solar/chlorine rise more rapidly (from 0.33 ∼ 61.34% to 94.23 ∼ 99.09%) than those in UV/chlorine system (from 19.14 ∼ 99.60% to 96.75 ∼ 99.88%). The pH-dependent contributions of various radical species are attributed to structure-dependent reactivities of compounds and pH-dependent concentrations of radical species. As the dose of Br - increases from 0 to 10 μM, the contributions of BrO • to the removal of aromatics (except for benzoic acid) increase from 0% to 10.28 ∼ 19.32%, thanks to the increased [BrO • ] ss . This work is necessary for enhancing the understanding of the pH-dependent contributions of individual species during the removal of dissociable aromatic contaminants in light/chlorine systems.