Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA, USA.
Environ Sci Technol. 2011 Aug 1;45(15):6329-35. doi: 10.1021/es200825g. Epub 2011 Jul 7.
According to the pseudo-ideal mixing assumption employed in practically all chemical transport models, organic aerosol components from different sources interact with each other in a single solution, independent of their composition. This critical assumption greatly affects modeled organic aerosol concentrations, but there is little direct experimental evidence to support it. A main experimental challenge is that organic aerosol components from different sources often look similar when analyzed with an aerosol mass spectrometer. We developed a new experimental method to overcome this challenge, using isotopically labeled compounds ((13)C or D) and a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). We generated mixtures of secondary organic aerosol (SOA) from isotopically labeled toluene and from unlabeled α-pinene and used the HR-ToF-AMS data to separate these different SOA types. We evaluated their interaction by comparing the aerosol mass yields of toluene and α-pinene when the SOA was formed in these mixtures to their yields when the SOA was formed in isolation. At equilibrium, our results are consistent with pseudo-ideal mixing of anthropogenic and biogenic SOA components from these chemically dissimilar precursors.
根据几乎所有化学输送模型中采用的准理想混合假设，来自不同来源的有机气溶胶成分在单一溶液中相互作用，与其组成无关。这一关键假设极大地影响了模型化的有机气溶胶浓度，但几乎没有直接的实验证据支持这一假设。一个主要的实验挑战是，当用气溶胶质谱仪分析时，来自不同来源的有机气溶胶成分通常看起来相似。我们开发了一种新的实验方法来克服这一挑战，使用同位素标记化合物（(13)C 或 D）和高分辨率飞行时间气溶胶质谱仪（HR-ToF-AMS）。我们生成了同位素标记的甲苯和未标记的α-蒎烯的二次有机气溶胶（SOA）混合物，并使用 HR-ToF-AMS 数据将这些不同的 SOA 类型分离。我们通过比较 SOA 形成于这些混合物中的甲苯和α-蒎烯的气溶胶质量产率与 SOA 形成于单独时的产率来评估它们的相互作用。在平衡状态下，我们的结果与这些化学上不同的前体的人为和生物源 SOA 成分的准理想混合一致。
