Kinetics and mechanism of •OH-initiated atmospheric oxidation of organophosphorus plasticizers: A computational study on tri-p-cresyl phosphate

Understanding the atmospheric fate of organophosphorus plasticizers is important for their environmental risk assessment. However, limited information is available at present. In this study, density functional theory (DFT) calculations were performed to investigate the transformation mechanism and kinetics of tri-p-cresyl phosphate (TpCP) initiated by (OH)-O-center dot. Results show that the initial reactions are dominated by H-abstraction and (OH)-O-center dot addition to form TpCP-radical, TpCP OH adducts and aryl phosphodiester. The H-abstraction pathways are more favorable than the (OH)-O-center dot addition pathways. The TpCP-radical and TpCP OH adducts can further react with 02 in the atmosphere to finally form benzaldehyde phosphate, hydroxylated TpCP and bicyclic radicals. Based on the transition state theory, the calculated rate constant (K-OH) of TpCP with (OH)-O-center dot at T = 298 K is 1.9 x 10(-12) cm(3) molecule(-1) s(-1) with an atmospheric lifetime of 4.2 days, which demonstrates that gaseous TpCP is atmospherically persistent. This study provides a comprehensive investigation of the,OH-initiated oxidation of TpCP, which is useful for understanding its mechanism of transformation and evaluating the risk in atmospheric environment. (C) 2018 Elsevier Ltd. All rights reserved.