Enhanced formation of bromophenols by anthraquinone-2-sulfonate and benzophenone: implications for photochemical production of organobromine compounds by dissolved organic matter in a marine environment*

Environmental context Organobromine compounds are a potential environmental hazard, but there are many uncertainties about their natural sources. This paper investigated the photochemical generation of bromophenols in the presence of dissolved organic matters (DOMs) and proxies, and demonstrated that DOMs enhance the photobromination reaction. The result indicates that the bromination process induced by sunlit DOMs likely contributes to the natural sources of organobromine compounds in the marine environment. Abstract Organobromine compounds are substantial environmental hazards owing to their high toxicity on organisms. Here we study the photochemical formation of bromophenols from phenol in bromide aqueous solutions (0.8–80 mM) in the presence of anthraquinone-2-sulfonate (AQ2S) and benzophenone (BP), which were adopted as the proxies of dissolved organic matter (DOM) having quinones and aromatic ketones structures. The formation of bromophenols increased with the increase of the concentrations of AQ2S and BP, and the promotion effect was in the order AQ2S > BP. Bromide and chloride ions were found to promote the formation of bromophenols. Moreover, natural DOM from Suwannee River was found to enhance this photobromination reaction at a low concentration (1 mg L−1). These results demonstrate the generation of reactive halogen species from sunlit DOM, and such a process could account for the abiotic source of organobromine compounds in a marine environment, as terrestrial DOM distributes universally in estuaries and coastal seawater and could diffuse to the open sea.