Secondary organic aerosol formation from photochemical aging of light-duty gasoline vehicle exhausts in a smog chamber
Secondary organic aerosol formation from photochemical aging of light-duty gasoline vehicle exhausts in a smog chamber
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DOI：
10.5194/acp-15-9049-2015
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发表时间：
2015-08
影响因子：
6.3
通讯作者：
Tingting Liu;Xinming Wang;W. Deng;Q. Hu;Xiang Ding;Yanli Zhang;Quanfu He;Zhangang Zhang;
中科院分区：
文献类型：
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作者：
Tingting Liu;Xinming Wang;W. Deng;Q. Hu;Xiang Ding;Yanli Zhang;Quanfu He;Zhangang Zhang;
抽象的。在中国，乘用车的快速增长导致人们越来越关注汽车尾气作为受灰霾影响的特大城市人为二次有机气溶胶（SOA）的重要来源。在一个30 m3的烟雾室中，对两辆在中国运行的轻型汽油车（LDGVs）（欧1和欧4）怠速排放的SOA形成进行了研究。在25 °C下进行五次光氧化实验，相对湿度约为50%。在5 × 106分子cm−3 h的OH暴露下老化后，形成的SOA是一次有机气溶胶（POA）的12-259倍。SOA生产因子（PF）为0.001-0.044 g kg−1燃料，与先前研究中的OH暴露量相当。然而，这种相当低的OH暴露比在典型的大气条件下，可能会导致低估的SOA的形成潜力从LDGV。在这项研究中，有效的SOA产量很好地拟合的一个产品的气体-颗粒分配模型，但相当低于以前的研究调查SOA的形成从三个空转乘用车（欧2-4）。传统的单环芳香族前体和萘可以解释形成的SOA的51- 90%。非物种物种，如支链和环状烷烃可能是原因不明的SOA的前体。使用高分辨率飞行时间气溶胶质谱仪来表征SOA的化学组成。汽油车尾气SOA的f43（主要是C2 H3 O+的m/z43与质谱总信号的比值）和f44（主要是CO2+）之间的关系与环境半挥发性含氧有机气溶胶（SV-OOA）相似。我们在货车Krevelen图中绘制SOA的O：C和H：C摩尔比。ΔH的斜率：C / ΔO：C的范围为−0.59至−0.36，表明这些实验中的氧化化学是羧酸和醇/过氧化物形成的组合。
Abstract. In China, a rapid increase in passenger vehicles has led to the growing concern of vehicle exhaust as an important source of anthropogenic secondary organic aerosol (SOA) in megacities hard hit by haze. In this study, the SOA formation of emissions from two idling light-duty gasoline vehicles (LDGVs) (Euro 1 and Euro 4) operated in China was investigated in a 30 m3 smog chamber. Five photo-oxidation experiments were carried out at 25 °C with relative humidity at around 50 %. After aging at an OH exposure of 5 × 106 molecules cm−3 h, the formed SOA was 12–259 times as high as primary organic aerosol (POA). The SOA production factors (PF) were 0.001–0.044 g kg−1 fuel, comparable with those from the previous studies at comparable OH exposure. This quite lower OH exposure than that in typical atmospheric conditions might however lead to the underestimation of the SOA formation potential from LDGVs. Effective SOA yields in this study were well fit by a one-product gas-particle partitioning model but quite lower than those of a previous study investigating SOA formation from three idling passenger vehicles (Euro 2–4). Traditional single-ring aromatic precursors and naphthalene could explain 51–90 % of the formed SOA. Unspeciated species such as branched and cyclic alkanes might be the possible precursors for the unexplained SOA. A high-resolution time-of-flight aerosol mass spectrometer was used to characterize the chemical composition of SOA. The relationship between f43 (ratio of m/z 43, mostly C2H3O+, to the total signal in mass spectrum) and f44 (mostly CO2+) of the gasoline vehicle exhaust SOA is similar to the ambient semi-volatile oxygenated organic aerosol (SV-OOA). We plot the O : C and H : C molar ratios of SOA in a Van Krevelen diagram. The slopes of ΔH : C / ΔO : C ranged from −0.59 to −0.36, suggesting that the oxidation chemistry in these experiments was a combination of carboxylic acid and alcohol/peroxide formation.