Terrestrial vegetation is a major global source of atmospheric secondary organic aerosol (SOA) through oxidation of biogenic volatile organic compound (BVOC) emissions. Climate change is altering the composition of BVOC emissions by increasing the prevalence of plant stress conditions, such as frequency and intensity of herbivorous insect outbreaks. The impact this will have on SOA formation is unknown. This laboratory study investigated the influence of aphid herbivory (Uroleucon macolai) on SOA formation from emissions of a common riparian shrub in California, Baccharis salicifolia (Asteraceae). Aphid herbivory increased the relative contribution of β-ocimene and decreased the relative contribution of β-guaiene in the BVOC emission profile. These effects on BVOC emissions did not translate to a significant aphid effect on SOA mass yields. However, for both control and aphid experiments, the fraction of total acyclic monoterpenes in the BVOC emission profile was correlated with reduced SOA mass yield. This is the first study to demonstrate a clear reduction in SOA mass yield as the proportion of acyclic terpenes in a complex BVOC mixture increased. These findings highlight the importance of better understanding acyclic terpene chemistry in the atmosphere to improve predictions of SOA in both current and future climates.

中文翻译：

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无环萜烯减少了河岸灌木排放的二次有机气溶胶形成。

通过氧化生物挥发性有机化合物（BVOC）的排放物，陆地植被是大气中次级有机气溶胶（SOA）的主要全球来源。气候变化通过增加植物胁迫条件（例如草食性昆虫暴发的频率和强度）的发生率，正在改变BVOC排放的构成。这对SOA形成的影响尚不清楚。该实验室研究调查了蚜虫取食（影响莴苣指管macolai从一个共同的河岸灌木的排放量在加州）在SOA的形成，Baccharis柳叶（菊科）。蚜虫食草在BVOC排放曲线中增加了β-ocimene的相对贡献，并减少了β-guaiene的相对贡献。这些对BVOC排放的影响并未转化为对SOA大量产量的明显蚜虫影响。但是，对于对照和蚜虫实验而言，BVOC排放曲线中总无环单萜的比例与SOA产量降低有关。这是第一个证明SOA大量生产量明显减少的研究，因为复杂的BVOC混合物中无环萜烯的比例增加了。这些发现强调了更好地了解大气中无环萜烯化学对改善当前和未来气候下SOA预测的重要性。