机动车排放物中低挥发性有机物的光氧化：有机气溶胶质量的产生和化学演化。
Photo-oxidation of low-volatility organics found in motor vehicle emissions: production and chemical evolution of organic aerosol mass.
机构信息
Departments of Mechanical Engineering and Chemical Engineering and Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
出版信息
Environ Sci Technol. 2010 Mar 1;44(5):1638-43. doi: 10.1021/es902635c.
Recent research has proposed that low-volatility organic vapors are an important class of secondary organic aerosol (SOA) precursors. Mixtures of low-volatility organics were photo-oxidized in a smog chamber under low- and high-NO(x) conditions. Separate experiments addressed emission surrogates (diesel fuel and motor oil) and single components (n-pentacosane). Both diesel fuel and motor oil are major components of exhaust from diesel engines. Diesel fuel is a complex mixture of intermediate volatility organic compounds (IVOCs), whereas motor oil is a complex mixture of semivolatile organic compounds (SVOCs). IVOCs exist exclusively in the vapor phase, while SVOCs exist in both the aerosol and vapor phase. Oxidation of SVOC vapors (motor oil and n-pentacosane) creates substantial SOA, but this SOA is largely offset by evaporation of primary organic aerosol (POA). The net effect is a cycling or pumping of SVOCs between the gas and particle phases, which creates more oxygenated organic aerosol (OA) but little new OA mass. Since gas-phase reactions are much faster than heterogeneous ones, the processing of SVOC vapors likely contributes to the production of highly oxidized OA. The interplay between gas-particle partitioning and chemistry also blurs traditional definitions of POA and SOA. Photo-oxidation of diesel fuel (IVOCs) rapidly creates substantial new OA mass, similar to published aging experiments with dilute diesel exhaust. However, aerosol mass spectrometer (AMS) data indicated that the SOA formed from emission surrogates is less oxidized than either the oxygenated organic aerosol (OOA) measured in the atmosphere or SOA formed from the photo-oxidation of dilute diesel exhaust. Therefore, photo-oxidation of IVOCs helps explain the substantial SOA mass produced from aging diesel exhaust, but some component is missing from these emission surrogate experiments that leads to the rapid production of highly oxygenated SOA.
最近的研究提出，低挥发性有机蒸气是重要的次生有机气溶胶（SOA）前体。在低和高氮氧化物（NOx）条件下，在烟雾室中光氧化低挥发性有机物混合物。单独的实验涉及排放替代物（柴油燃料和机油）和单一组分（正二十五烷）。柴油燃料和机油都是柴油发动机尾气的主要成分。柴油燃料是中间挥发性有机化合物（IVOCs）的复杂混合物，而机油是半挥发性有机化合物（SVOCs）的复杂混合物。IVOCs 仅存在于气相中，而 SVOCs 存在于气溶胶和气相中。SVOC 蒸气（机油和正二十五烷）的氧化会产生大量 SOA，但这部分 SOA 被初级有机气溶胶（POA）的蒸发所抵消。净效应是 SVOC 从气相到颗粒相的循环或泵送，这会产生更多含氧有机气溶胶（OA），但新 OA 质量很少。由于气相反应比多相反应快得多，因此 SVOC 蒸气的处理可能会导致高度氧化的 OA 的产生。气相和颗粒相之间的分配和化学相互作用也模糊了 POA 和 SOA 的传统定义。柴油燃料（IVOCs）的光氧化迅速产生大量新的 OA 质量，类似于已发表的用稀柴油尾气进行老化实验。然而，气溶胶质谱仪（AMS）数据表明，与在大气中测量的含氧有机气溶胶（OOA）或从稀柴油废气光氧化形成的 SOA 相比，从排放替代物形成的 SOA 氧化程度较低。因此，IVOCs 的光氧化有助于解释从老化柴油尾气中产生的大量 SOA 质量，但这些排放替代物实验中缺少一些成分，导致高度氧化的 SOA 快速产生。
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