| Chlorine radicals（·Cl）have a high oxidation ability toward organic pollutants.The new findings of·Cl in mid-continental areas increase the importance of·Cl in transforming atmospheric organic pollutants.In addition,the reaction mechanism of atmospheric organic pollutants initiated by·Cl is not always the same as corresponding one initiated by hydroxyl radicals（·OH）,the most important active oxygen species in the atmosphere,due to the structure difference between the·Cl and·OH.This implies that the atmospheric fates and environmental risks of organic pollutants initiated by·Cl may differ from those by·OH.Hence,it is essential to study the atmospheric transformation of organic pollutants initiated by·Cl.Amines are one kind of atmospheric pollutants with potential environmental risk.About 160 different amines have been identified in the atmosphere.Current studies showed that the reactions of amines initiated by·Cl can form carcinogenic nitrosamine and the formation of carcinogenic nitrosamines has the structure dependence of amines.The dependence comes from two aspects.On the one hand,the formation of N-center radicals,the precursors of nitrosamines,has the structure dependence in the reactions of amines with·Cl.On the other hand,the yield of carcinogenic nitrosamines depends on the structure of N-center radicals in the competitive reactions of N-center radicals with O2 and NO.Therefore,it is important to investigate the structural effect of amines on the formation of N-center radicals and carcinogenic nitrosamines to comprehensively understand the environmental risks caused by amine emission.In this thesis,the reaction mechanism and kinetics of cyclic amines initiated by·Cl were investigated by quantum chemistry calculation and kinetics simulation.In addition,based on the previous studies,the factors that affect the formation of nitrosamines were analyzed and the model to predict the formation yield of nitrosamines was developed.The specific investigated contents and results as follows:（1）The atmospheric transformations of morpholine（MOR）,piperidine（PIP）and pyrrolidine（PYR）initiated by·Cl were investigated.The results indicated that the most favorable reaction pathway is H-abstraction reaction occurring at NH site to form N-center radicals for these three cyclic amines.At 1 atm and 298 K,the overall reaction rate constants(kCl)for the reactions of MOR,PIP and PYR with·Cl are calculated to be 5.0?10-10,5.1?10-10 and 4.9?10-10 cm3 molecule-1 s-1,respectively.The formed N-center radicals either mainly react with NO to form carcinogenic nitrosamines,or mainly react with O2 to form imines.Therefore,these N-center radicals have different atmospheric fates.Based on the previous and our studies on the reactions of N-center radicals with O2/NO,we concluded that the reaction rate constants of N-center radicals with O2(kO2)is the important factor in determining the yields of nitrosamines produced from N-center radicals.（2）A three-step scheme including mechanistic analysis and kinetics calculation of the reactions of 28 various N-center radicals with O2,and model development was took to solve the kO2 data shortage.The reaction mechanisms and kinetics of 28 N-center radicals with O2are investigated by the computational simulation methods.The direct H-abstraction was found to be the most favorable reaction pathway for the reactions of all 28 N-center radicals with O2.The specific molecular conformation and the C-H bond energy of the N-center radicals are two important factors to determine kO2 values.Based on the mechanistic understanding of kO2values,a quantitative structure-activity relationship（QSAR）model of kO2 values was developed.The model has satisfactory goodness-of-fit,robustness and predictive ability.The determined k O2 values and the in silico methods provide a scientific base for assessing formation risk of toxic nitrosamines in the atmosphere.All of above,the results of this thesis can provide the indispensable data in evaluating the atmospheric fates and environmental risks of amines comprehensively,and enrich the knowledge of·Cl chemistry. |
