Degradation of carbamazepine in ice with bromate and nitrite: Role of reactive nitrogen species.

ABSTRACT

Seasonal freezing of waters occurs during winter in cold regions. Bromate ( [Formula see text] ) is a disinfection by-product generated during water treatment, its interaction with emerging contaminants may be affected by freezing. Nitrite ( [Formula see text] ) is widely distributed in the environment, whereas its effect on the interaction of emerging contaminants and [Formula see text] in ice may have been overlooked. Herein carbamazepine (CBZ) was selected as a model emerging contaminant to elucidate the role of reactive nitrogen species (RNS) in contaminant transformation during the reduction of [Formula see text] by [Formula see text] in ice. Results indicated that freezing significantly enhanced CBZ degradation by [Formula see text] . The CBZ degradation by [Formula see text] and [Formula see text] in ice was 25.4 %-27.8 % higher than that by [Formula see text] . Contributions of hydroxyl radical (•OH), bromine radical (•Br), and RNS to CBZ degradation in freezing/dark or sunlight systems were 8.1 % or 15.9 %, 25.4 % or 7.2 %, and 66.5 % or 76.9 %, respectively. Most CBZ was degraded by RNS generated during the reduction of [Formula see text] by [Formula see text] in ice, resulting in 16.4 % of transformation products being nitro-containing byproducts. Hybrid toxicity of CBZ/ [Formula see text] / [Formula see text] system was reduced effectively after the freezing-sunlight process. This study can provide new insights into the environmental fate of emerging contaminants, [Formula see text] , and [Formula see text] in cold regions.