We used unlabeled and deuterium-labeled precursors to generate and characterize secondary organic aerosol (SOA), a class of atmospheric constituents that rank among the least understood in the climate system, while circumventing the typical problems caused by spectral similarity of SOA mass fragments in aerosol mass spectrometry. We used highly sensitive single-particle mass spectrometers to measure mixing via semi-volatile gas-phase exchange between SOA from biogenic precursors (terpenes) and an anthropogenic precursor (toluene). These are common laboratory mimics for ambient SOA. The experiments showed that particles derived from isoprene and α-pinene ozonolysis undergo fast exchange via evaporation and condensation of semi-volatile constituents without any signs of diffusion limitations, even when the relative humidity (RH) is <10%. Particles derived from limonene ozonolysis showed slower exchange than those from α-pinene because of their more polar constituents and resulting lower diffusivity. Finally, particles derived from β-caryophyllene ozonolysis showed limited vapor uptake even for RH ≫ 30%.

我们使用未标记和氘标记的前体来生成和表征次要有机气溶胶（SOA），这是在气候系统中了解最少的一类大气成分，同时规避了由气溶胶中SOA质量碎片的光谱相似性引起的典型问题质谱。我们使用了高灵敏度的单颗粒质谱仪，通过来自生物前体（萜烯）和人为前体（甲苯）的SOA之间的半挥发性气相交换来测量混合。这些是环境SOA的常见实验室模拟。实验表明，即使相对湿度（RH）<10％，来自异戊二烯和α-pine烯臭氧分解的颗粒也会通过半挥发性成分的蒸发和缩合进行快速交换，而没有任何扩散限制的迹象。柠檬烯臭氧分解衍生的颗粒与α-pine烯相比，交换速度较慢，这是因为它们的极性成分更多，且扩散系数较低。最后，衍生自β-石竹烯臭氧分解的颗粒即使在相对湿度为particles 30％时也显示出有限的蒸气吸收。