Atmospheric Transformation Mechanism And Kinetics Of Alternatives Of Polybrominated Diphenyl Ethers Initiated By OH Radical

Emerging brominated flame retardants and organophosphorus flame retardants as the alternatives of polybrominated diphenyl ethers(PBDEs)have been frequently detected in the atmosphere.Especially in the polar region,their detected concentration was even higher than that of widely concerned PBDEs.Now,the alternatives of PBDEs have become the pollutants with potential environmental risk.According to the general knowledge on transformation of organic pollutants in the atmosphere and the structural feature of the alternatives of PBDEs,the reactions of the alternatives of PBDEs with ?OH should be their important removal way.Therefore,in the view of the environmental risk evaluation on the pollutants,it is essential to reveal the atmospheric chemistry of alternatives of polybrominated diphenyl ethers initiated by ?OH.In this study,a combined quantum chemical method with kinetics modeling were used to investigate atmospheric transformation mechanism and kinetics of AFRs initiated by ?OH in the presence of O2/NOx(x=1,2),taking triphenyl phosphate(TPhP)and 1,2-Bis(2,4,6-tribromophenoxy)ethane(BTBPE)as cases.Results show that the pathway involving initial ?OH addition to phenyl of TPhP to form TPhP-OH adduct is the most favorable;as for BTBPE + ?OH,hydrogen abstraction from-CH2-CH2-group of BTBPE,different from ?OH addition mechanism of PBDEs,is found to be favorable in the initial reactions.Subsequently,we probed the mechanism,kinetics and product distribution of the reaction of the active intermediates formed in the initiatal reaction and O2/NOx.According to calculated overall reaction rate constants,we evaluated the atmospheric lifetime of these two AFRs at 298 K.The lifetime of TPhP and BTBPE is 7.6 and 11.8 days,respectively,clarifying that gaseous TPhP and BTBPE have atmospheric persistence for the first time.Furthermore,H2 O molecule and ice surface(H2O-48),as cases of ubiquitous water in the atmosphere,were chosen to invesgate the influence on mechanism of TPhP/BTBPE + ?OH.It was found that atmospheric ice surface has little effect on the kinetics of the rate-determining step in the reaction of TPhP/BTBPE + ?OH.H2 O molecule has little effect on the additon reaction of phenyl for TPh P,however,it will catalyze the transformation of BTBPE via hydrogen-bond interaction.As stated above,in this thesis,we investigated the reaction mechanism and kinetics of the representative AFRs(TPhP/BTBPE)with ?OH and predicted their atmospheric lifetime and product distribution;explored the influence of atmospheric water on the reactions.The results are significant for the environmental risk evaluation about the alternatives of PBDEs,and enrich the knowledge about the effect of water on the transformation of organic pollutants in the atmosphere.