The potential environmental behavior and risks of TBECH transformation initiated by reactive oxygen species in natural waters and AOPs

1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH), as an emerging pollutant, was often detected in the aquatic environments, but the chemical behavior and potential eco-toxicity of each stereoisomer are poorly understood. Here, the chemical behavior of TBECH stereoisomers under the oxidation of ROS (OH center dot and HO2 center dot) in the aqueous phase was investigated by computational chemistry. Besides, the eco-toxicity effects of TBECH and representative transformation products were obtained by computational toxicology. In the natural environments, TBECH stereoisomers could be transformed under the initiation of ROS, and the key oxidation species is OH center dot rather than HO2 center dot in this process. DOM could indirectly promote the transformation of TBECH stereoisomers, resulting in the half-life (t(1/2)) of TBECH stereoisomers in less than 180 days, thus no longer maintaining environmental persistence. Although TBECH stereoisomers may show environmental persistence in natural waters, AOPs based on OH center dot could bring about their rapid transformation, which predicts the effectiveness of OH-based AOPs for the treatment of TBECH wastewater. The results of the eco-toxicity assessment showed that the transformation of TBECH stereoisomers is beneficial to the reduction of toxicity, but the transformation products are not completely harmless. Thus, it is urgent to clarify the environmental behaviors and risks of these transformation products that remain toxic in the aquatic environments.