Environmental Photochemical Behavior Of Tetrabromobisphenol A/S And Its Analogues In Seawater

Tetrabromobisphenol A/S?TBBPA/S?and its analogues are emerging pollutants that have been frequently detected in the environment.It is of great significance to understand their environmental transformation behavior for the risk assessment of these pollutants.Previous studies showed that photochemical transformation of TBBPA can occur in the aqueous solution,however,these studies mainly focused on fresh water.Ocean is an important sink of pollutants in the environment,and the photodegradation behavior of TBBPA in seawater remains to be further studied.In addition,the structures of TBBPS and TBBPA/S analogues are similar to TBBPA,but their photochemical behavior in aquatic environments has not been reported.Therefore,TBBPA,TBBPS and two analogues were selected as model compounds to investigate the photochemical behavior in seawater.The main research contents and results are as follows:?1?The photodegradation kinetics of TBBPA and TBBPS in pure water,freshwater and seawater were investigated under simulated sunlight irradiation.Results show that the photodegradation rates of TBBPA and TBBPS in seawater are slower than that in pure water and freshwater,water constituents such as dissolved organic matter?DOM?and halogen ions in seawater can inhibit the photodegradation of TBBPA and TBBPS.DOM extracted from the Yellow Sea seawater?H-DOM?and the Suwannee River natural organic matter?SRNOM?were selected to investigate the effects of DOM on the photodegradation of TBBPA and TBBPS.Results indicate that DOM can inhibit the photodegradation via competitive light absorption,and the inhibition of H-DOM is weaker than that of SRNOM.Cl^-inhibits the photodegradation of TBBPA by quenching singlet oxygen?¹O₂?and triplet excited TBBPA,and inhibits the photodegradation of TBBPS by quenching hydroxyl radical?·OH?and triplet excited TBBPS.Br^-and the ionic strength effect of Cl^-have no obvious effects on the photodegradation.Based on the determined parameters,photodegradation rate constants of TBBPA and TBBPS in the Yellow River Delta freshwater,estuarine water and seawater were predicted.The rates of TBBPA and TBBPS in the surface seawater are the slowest;nevertheless the rate constants in seawater become higher than those in the freshwater and estuarine water at a depth of 0.05 m.?2?The photodegradation rates of tetrabromobisphenol A-bis?diallyl ether??TBBPA-BAE?and tetrabromobisphenol S-bis?2,3-dibromopropyl ether??TBBPS-BDBPE?are faster in seawater than that in pure water and freshwater.The photodegradation of TBBPA-BAE and TBBPS-BDBPE could be promoted by SRNOM and H-DOM via generate·OH,¹O₂ and triplet excited DOM,and the promotion of H-DOM is stronger than that of SRNOM.For SRNOM,the effects to promote the photodegradation of TBBPA-BAE and TBBPS-BDBPE are enhanced with increasing the concentration.Cl^-and Br^-also can promote the photodegradation of TBBPA-BAE and TBBPS-BDBPE,but the ionic strength has no obvious effects on the photodegradation.