烯烃臭氧化反应产生的Criegee中间体（CI）是以往未识别的重要大气氧化剂，对硫酸盐及二次有机气溶胶的生成可能具有重要作用，并与大气中硫酸以至新粒子形成密切相关。然而对CI大气化学反应机理的认识还十分欠缺，制约相关研究的主要瓶颈之一是缺乏对CI的检测手段。本项目拟研发一种基于大气常压界面化学电离质谱技术的新型CI检测方法并通过对关键硬件的技术研发完成一套专用CI检测质谱仪。其工作原理为：先使CI与过量5,5-二甲基-1-吡咯啉氮氧化物（DMPO）反应生成稳定衍生物，再使用水合氢质子的水分子簇使其质子化并被飞行时间质谱仪检测。本项目优势不仅在于可对CI进行实时、在线测量还可区分CI化学种类并以硫酸气体为中介标准物实现对CI检测的标定。基于我国烯烃产业规模及其对灰霾形成的潜在巨大影响，研发高灵敏度CI检测方法、开展相关研究是充分认识我国SOA形成机制，制定有效灰霾防控政策的客观需要之一。

Criegee intermediate (CI) formed by alkene ozonolysis is unprecedentedly recognized as an important atmospheric oxidant. CI may play crucial roles in the production of particulate sulfate and secondary organic aerosol (SOA) and may be the underline cause of gaseous sulfuric acid formation and ensuing nucleation events. However, our understanding of CI-related reaction mechanism is still incomplete, which is mainly the result of lacking of proper CI detection techniques to conduct CI-related researches. Therefore, we propose to develop a new method to do online and real-time CI measurements, which will be based on atmospheric pressure interface chemical ionization mass spectrometry. A new instrument will be developed and completed from this project. Its working principle is that CI will firstly react with excess 5,5-dimethyl-pyrroline N-oxide (DMPO) to form a stabilized adduct, which then will be protonated by the water clusters of hydronium ions and detected by a time-of-flight mass spectrometer. The unique advantage of this method is that not only can CI be detected online in real-time, but that CI speciation and quantification can be achieved. Given the scale of alkene-related industry in China and its potential contribution to haze formation, it is necessary to develop sensitive CI detection methods and to conduct related researches to fully comprehend the SOA formation mechanism in China and thus to establish effective haze mitigation strategies.