Real-time Measurements of Secondary Organic Aerosol from the Photooxidation of Naphthalene using Single Particle Mass Spectrometry
作者单位：Insitute of Earth EnvironmentChinese Academy of Sciences Department of Chemistry and Environmental Research InstituteUniversity College Cork
会议名称：《十一届全国气溶胶会议暨第十届海峡两岸气溶胶技术研讨会》
会议日期：2013年
学科分类：07[理学] 070602[理学-大气物理学与大气环境] 0706[理学-大气科学]
关 键 词：Secondary Organic Aerosol Naphthalene online single particle mass spectrometer
摘 要：Naphthalene is the most abundant polycyclic aromatic hydrocarbon detected in urban air and has recently been identified as an important precursor for the formation of secondary organic aerosol（SOA） in the atmosphere. In this work, a series of simulation chamber experiments has been performed on the photooxidation of naphthalene under a variety of reaction conditions. The decay of naphthalene was monitored using in situ FTIR spectroscopy and the formation and evolution of SOA was followed using a scanning mobility particle sizer. An Aerosol Time-of-Flight Mass Spectrometer（ATOFMS） was used to determine the chemical composition of the SOA in real-time. In experiments using NOx as the hydroxyl radical precursor, the single particle mass spectra were found to change slowly over a period of hours. The positive ion mass spectra initially contained hydrocarbon fragments typical of aromatic species which are tentatively attributed to ring-retaining oxidation products such as naphthol and nitronaphthalene. After 3-4 hours the intensity of the hydrocarbon fragments was significantly reduced and the negative ion mass spectra displayed characteristic features of oxidized organic aerosol and nitrates. Interestingly, some of these peaks continued to increase after the lights were turned off, suggesting that particle phase processing was maintained, even under dark conditions. The results from these experiments indicate that ATOFMS can be used to monitor chemical changes in SOA in real-time and is a potentially useful tool for investigating aerosol formation and ageing.