PDF(Pubmed)
Abstract：
On-road gasoline vehicles are a major source of secondary organic aerosol (SOA) in urban areas. We investigated SOA formation by oxidizing dilute, ambient-level exhaust concentrations from a fleet of on-road gasoline vehicles in a smog chamber. We measured less SOA formation from newer vehicles meeting more stringent emissions standards. This suggests that the natural replacement of older vehicles with newer ones that meet more stringent emissions standards should reduce SOA levels in urban environments. However, SOA production depends on both precursor concentrations (emissions) and atmospheric chemistry (SOA yields). We found a strongly nonlinear relationship between SOA formation and the ratio of nonmethane organic gas to oxides of nitrogen (NOx) (NMOG:NOx), which affects the fate of peroxy radicals. For example, changing the NMOG:NOx from 4 to 10 ppbC/ppbNOx increased the SOA yield from dilute gasoline vehicle exhaust by a factor of 8. We investigated the implications of this relationship for the Los Angeles area. Although organic gas emissions from gasoline vehicles in Los Angeles are expected to fall by almost 80% over the next two decades, we predict no reduction in SOA production from these emissions due to the effects of rising NMOG:NOx on SOA yields. This highlights the importance of integrated emission control policies for NOx and organic gases.
摘要：
道路汽油车是城市地区二次有机气溶胶（SOA）的主要来源。我们研究了氧化稀的SOA形成，烟雾室中道路汽油车队的环境水平废气浓度。我们测量了满足更严格排放标准的新型车辆的SOA形成。这表明，用符合更严格排放标准的较新车辆自然替代较旧车辆应该会降低城市环境中的SOA水平。然而,SOA生产取决于前体浓度（排放）和大气化学（SOA产量）。我们发现SOA形成与非甲烷有机气体与氮氧化物（NOx）（NMOG：NOx）之比之间存在强烈的非线性关系，影响过氧自由基的命运。例如,将NMOG：NOx从4更改为10ppbC/ppbNOx，使稀汽油汽车尾气的SOA产量增加了8倍。我们调查了这种关系对洛杉矶地区的影响。尽管洛杉矶汽油车的有机气体排放量预计在未来20年内将下降近80%，我们预测，由于NMOG：NOx对SOA产量的影响，这些排放不会减少SOA产量。这突出了NOx和有机气体综合排放控制政策的重要性。
