Bahreini R, Keywood M D, Ng N L, Varutbangkul V, Gao S, Flagan R C, Seinfeld J H, Worsnop D R, Jimenez J L
Department of Environmental Science and Engineering, California Institute of Technology, Mail Code 210-41, 1200 East California Boulevard, Pasadena, California 91125, USA.
Environ Sci Technol. 2005 Aug 1;39(15):5674-88. doi: 10.1021/es048061a.
The Aerodyne aerosol mass spectrometer (AMS) was used to characterize physical and chemical properties of secondary organic aerosol (SOA) formed during ozonolysis of cycloalkenes and biogenic hydrocarbons and photo-oxidation of m-xylene. Comparison of mass and volume distributions from the AMS and differential mobility analyzers yielded estimates of "effective" density of the SOA in the range of 0.64-1.45 g/cm3, depending on the particular system. Increased contribution of the fragment at m/z 44, C02+ ion fragment of oxygenated organics, and higher "delta" values, based on ion series analysis of the mass spectra, in nucleation experiments of cycloalkenes suggest greater contribution of more oxygenated molecules to the SOA as compared to those formed under seeded experiments. Dominant negative "delta" values of SOA formed during ozonolysis of biogenics indicates the presence of terpene derivative structures or cyclic or unsaturated oxygenated compounds in the SOA. Evidence of acid-catalyzed heterogeneous chemistry, characterized by greater contribution of higher molecular weight fragments to the SOA and corresponding changes in "delta" patterns, is observed in the ozonolysis of alpha-pinene. Mass spectra of SOA formed during photooxidation of m-xylene exhibit features consistent with the presence of furandione compounds and nitro organics. This study demonstrates that mixtures of SOA compounds produced from similar precursors result in broadly similar AMS mass spectra. Thus, fragmentation patterns observed for biogenic versus anthropogenic SOA may be useful in determining the sources of ambient SOA.
使用Aerodyne气溶胶质谱仪（AMS）来表征环烯烃和生物源烃类臭氧化过程以及间二甲苯光氧化过程中形成的二次有机气溶胶（SOA）的物理和化学性质。根据特定系统，比较AMS和差分迁移率分析仪的质量和体积分布，得出SOA的“有效”密度估计值在0.64 - 1.45 g/cm³范围内。在环烯烃的成核实验中，基于质谱的离子系列分析，m/z 44处碎片（氧化有机物的CO₂⁺离子碎片）的贡献增加以及更高的“δ”值表明，与种子实验中形成的SOA相比，更多氧化分子对SOA的贡献更大。生物源物质臭氧化过程中形成的SOA的主要负“δ”值表明SOA中存在萜烯衍生物结构或环状或不饱和氧化化合物。在α-蒎烯的臭氧化过程中观察到酸催化非均相化学的证据，其特征是较高分子量碎片对SOA的贡献更大以及“δ”模式相应变化。间二甲苯光氧化过程中形成的SOA的质谱显示出与呋喃二酮化合物和硝基有机物存在一致的特征。这项研究表明，由相似前体产生的SOA化合物混合物会产生大致相似的AMS质谱。因此，生物源与人为源SOA观察到的碎裂模式可能有助于确定环境SOA的来源。
