Quantifying the Role of the Relative Humidity-Dependent Physical State of Organic Particulate Matter in the Uptake of Semivolatile Organic Molecules
Quantifying the Role of the Relative Humidity-Dependent Physical State of Organic Particulate Matter in the Uptake of Semivolatile Organic Molecules
复制标题
DOI：
10.1021/acs.est.9b05354
复制
发表时间：
2019-11-19
影响因子：
11.4
通讯作者：
Martin, Scot T.
中科院分区：
文献类型：
--
作者：
Han, Yuemei;Gong, Zhaoheng;Martin, Scot T.
研究了气相二羧酸对有机颗粒物（PM）的吸收，探讨了PM物理状态在气相半挥发性有机分子与有机PM交换过程中的作用。同源系列的探针分子，特别是同位素标记的C-13-二羧酸，与气溶胶质谱联用，以获得不同相对湿度（RH）的有机PM的摄取的定量表征。PM是由未标记的α-蒎烯的暗臭氧分解产生的。C-13标记的草酸，丙二酸和α-酮基谷氨酸的吸收逐步增加5至15倍，在RH从15%增加到80%。随着RH的增加而增强的吸收主要由颗粒相中的较高分子扩散率来解释，这与有机PM的物理状态从非液体状态到逐渐不那么粘稠的液体状态的变化有关。在高RH下，探针分子的粒子相的分区与物理化学相互作用的有机PM比与共吸收的液态水。摄取的探针分子也增加了挥发性沿着同源系列的减少。这项研究定量地显示了颗粒物理状态在有机PM与半挥发性有机分子相互作用中的关键作用。
The uptake of gas-phase dicarboxylic acids to organic particulate matter (PM) was investigated to probe the role of the PM physical state in exchange processes between gas-phase semivolatile organic molecules and organic PM. A homologous series of probe molecules, specifically isotopically labeled C-13-dicarboxylic acids, was used in conjunction with aerosol mass spectrometry to obtain a quantitative characterization of the uptake to organic PM for different relative humidities (RHs). The PM was produced by the dark ozonolysis of unlabeled alpha-pinene. The uptake of C-13-labeled oxalic, malonic, and alpha-ketoglutaric acids increased stepwise by 5 to 15 times with increases in RH from 15 to 80%. The enhanced uptake with increasing RH was explained primarily by the higher molecular diffusivity in the particle phase, as associated with changes in the physical state of the organic PM from a nonliquid state to a progressively less-viscous liquid state. At high RH, the partitioning of the probe molecules to the particle phase was more associated with physicochemical interactions with the organic PM than that with the co-absorbed liquid water. Uptake of the probe molecules also increased with a decrease in volatility along the homologous series. This study quantitatively shows the key roles of the particle physical state in governing the interactions of organic PM with semivolatile organic molecules.