大气中单萜烯与氯气、臭氧的反应动力学及机理研究

Monoterpenes are important species in atmospheric VOCs, and its atmospheric oxidation plays significant role in formation of second organic aerosol, and photooxidant. Hence, kinetic and mechanistic study about atmospheric oxidation of monoterpenes has received great interest. However, there are still large uncertainty in the rate constant and lack of temperature dependence of rate constant for reactions of some monoterpenes with ozone. There seems no kinetic and mechnistic data reported on the reaction of monoterpenes with molecular chlorine yet. By using indoor smog chamber, reactions of atmospheric monoterpenes with molecular chlorine and ozone are studied. Rate constants for the above reactions as well as their dependence on temperature will be measured by absolute or relative rate techniques. Impact of monoterpenes' reaction with molecular chlorine on the sink of atmospheric monoterpene will be evaluated. By investigating the major products as well as the formation yields, the mechanisms of reaction of monoterpene with molecular chlorine be discussed. The obtained kinetics and mechanisms data will be used to evaluate the contribution of monoterpene's dark reaction with chlorine on its atmospheric processes.

单萜烯是大气中重要的一类挥发性有机物，其在大气中的氧化反应对二次有机气溶胶以及光氧化剂形成具有重要作用，为此，大气中单萜烯的氧化反应动力学和机理研究受到广泛关注。目前部分单萜烯与O3反应速率常数测定结果存在很大的不确定性，而且缺乏反应速率常数对温度的依赖系数研究；关于单萜烯与Cl2反应的动力学和机理研究尚未见文献报道。本申请项目拟采用室内烟雾箱为手段,研究大气中单萜烯化合物与Cl2和O3的反应。通过绝对速率方法和相对速率方法，测定上述单萜烯反应的速率常数及其对温度的依赖系数，并评估单萜烯与Cl2暗反应对大气中单萜烯汇机制的重要性；研究单萜烯和Cl2暗反应体系的主要产物及其产率，认识单萜烯与Cl2暗反应的机理，进而为正确评估单萜烯与Cl2的暗反应对单萜烯大气化学过程的影响提供新的科学依据。

单萜烯是大气中重要的一类挥发性有机物，其在大气中的氧化反应对二次有机气溶胶以及光氧化剂形成具有重要作用，因此，大气中单萜烯的氧化反应动力学和机理研究受到广泛关注。目前部分单萜烯与O3以及与 Cl2的光化学反应速率常数测定结果存在很大的不确定性。本项目采用室内烟雾箱为手段，研究了大气中异戊二烯以及部分单萜烯化合物与Cl2和O3的光化学反应。通过绝对速率方法，测定了上述萜烯与O3反应的速率常数：(×10-17cm3molecule-1s-1)： k(O3+isoprene)=0.956，k(O3+α-pinene)=12.3，k(O3+β-pinene)=2.66，k(O3+γ-terpinene)=17.9，k(O3+ myrcene)=17.3，k(O3+limonene)=14.9，k(O3+2-carene)=21.3；单萜烯和Cl2在无光照条件下不发生暗反应，而Cl2在在365nm光照条件下光解产生氯原子，氯原子进一步与萜烯发生反应；通过相对速率法获得了上述萜烯与氯原子反应的速率常数(×10-10cm3molecule-1s-1)：k(Cl+isoprene)=3.97，k(Cl+ α-pinene)=3.93，k(Cl+β-pinene)=4.55，k(Cl+α-terpinene)=4.33，k(Cl+γ-terpinene)= 3.92，k(Cl+myrcene)=4.29，k(Cl+limonene)=4.55，k(Cl+2-carene)=4.19。本研究获得的速率常数为评估萜烯大气光化学反应的影响补充了新的数据。