Volatility Change during Droplet Evaporation of Pyruvic Acid
Volatility Change during Droplet Evaporation of Pyruvic Acid
复制标题
丙酮酸液滴蒸发过程中挥发性的变化
DOI：
10.1021/acsearthspacechem.0c00044
复制
发表时间：
2020
影响因子：
3.4
通讯作者：
Turpin, Barbara J.
中科院分区：
文献类型：
--
作者：
Petters, Sarah S.;Hilditch, Thomas G.;Tomaz, Sophie;Miles, Rachael E.;Reid, Jonathan P.;Turpin, Barbara J.
大气中的水溶性有机气体，如丙酮酸，是通过生物源和人为排放的光化学氧化而大量产生的，并在气溶胶和水成物中发生水介导的反应。这些反应可以通过形成挥发性较低的化合物来增加气溶胶的质量。虽然在了解相关的水化学方面取得了进展，但对液滴蒸发过程中发生的化学反应知之甚少。在这里，我们使用振动孔气溶胶发生器（VOAG）和电动平衡器（EDB）来研究丙酮酸液滴的蒸发。在某些情况下，丙酮酸首先被OH自由基氧化。氧化混合物的蒸发行为与基于已知反应产物挥发性的预期一致。然而，在不氧化的情况下进行独立的VOAG和EDB蒸发实验也得到了稳定的残余颗粒；预估产率为初始丙酮酸的10-30%。产率随温度和丙酮酸浓度在云、雾和气溶胶相关浓度上的变化而变化。低挥发性产物的形成，可能是环状二聚体，表明在液滴蒸发过程中发生的丙酮酸增加反应可能有助于大气中羰基的气体到颗粒的转化。
Atmospheric water-soluble organic gases such as pyruvic acid are produced in large quantities by photochemical oxidation of biogenic and anthropogenic emissions and undergo water-mediated reactions in aerosols and hydrometeors. These reactions can contribute to aerosol mass by forming less-volatile compounds. Although progress is being made in understanding the relevant aqueous chemistry, little is known about the chemistry that takes place during droplet evaporation. Here, we examine the evaporation of aqueous pyruvic acid droplets using both the vibrating orifice aerosol generator (VOAG) and an electrodynamic balance (EDB). In some cases, pyruvic acid was first oxidized by OH radicals. The evaporation behavior of oxidized mixtures was consistent with expectations based on known volatilities of reaction products. However, independent VOAG and EDB evaporation experiments conducted without oxidation also resulted in stable residual particles; the estimated volume yield was 10–30% of the initial pyruvic acid. Yields varied with temperature and pyruvic acid concentration across cloud-, fog-, and aerosol-relevant concentrations. The formation of low-volatility products, likely cyclic dimers, suggests that pyruvic acid accretion reactions occurring during droplet evaporation could contribute to the gas-to-particle conversion of carbonyls in the atmosphere.