Volatility and Oxidative Aging of Aqueous Maleic Acid Aerosol Droplets and the Dependence on Relative Humidity
Volatility and Oxidative Aging of Aqueous Maleic Acid Aerosol Droplets and the Dependence on Relative Humidity
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DOI：
10.1021/jp504823j
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发表时间：
2014-07-31
影响因子：
2.9
通讯作者：
Reid, Jonathan P.
中科院分区：
文献类型：
--
作者：
Dennis-Smither, Benjamin J.;Marshall, Frances H.;Reid, Jonathan P.
利用气溶胶光镊技术和腔增强拉曼光谱技术研究了含马来酸（MA）气溶胶单粒子的微物理结构和臭氧的非均相氧化作用。在一定的相对湿度范围内测定了MA从水滴中的蒸发速率，确定了纯组分的蒸气压为（1.7 +/- 0.2）× 10（-3）Pa。含水MA液滴的折射率（RI）随相对湿度（RH）的变化允许MA的过冷液体RI估计为1.481 +/-0.001。吸湿增长的测量结果与以前研究的平衡模型预测是一致的。同时测量的液滴的组成，尺寸和折射率已在臭氧分解过程中在RH的范围50- 80%，提供洞察有机产品的挥发性，液滴吸湿性的变化，和光学性能。将水性液滴暴露于臭氧导致形成具有从不挥发性到挥发性的广泛挥发性的产物。反应吸收系数显示臭氧浓度的依赖性较弱，但不依赖于RH或盐浓度。RI随时间的变化明显取决于氧化进行时的RH，甚至可以显示相反的趋势;而RI随着臭氧暴露在低相对湿度下而增加，当氧化在高相对湿度下进行时，RI降低。RI的变化与Cappa等人（J. Geophys. Res. 2011，116，D15204）。一旦被氧化，颗粒被证明在干燥时形成非晶相，而不是结晶，残留水的蒸发动力学缓慢。
The microphysical structure and heterogeneous oxidation by ozone of single aerosol particles containing maleic acid (MA) has been studied using aerosol optical tweezers and cavity enhanced Raman spectroscopy. The evaporation rate of MA from aqueous droplets has been measured over a range of relative humidities and the pure component vapor pressure determined to be (1.7 +/- 0.2) x 10(-3) Pa. Variation in the refractive index (RI) of an aqueous MA droplet with relative humidity (RH) allowed the subcooled liquid RI of MA to be estimated as 1.481 +/- 0.001. Measurements of the hygroscopic growth are shown to be consistent with equilibrium model predictions from previous studies. Simultaneous measurements of the droplet composition, size, and refractive index have been made during ozonolysis at RHs in the range 50-80%, providing insight into the volatility of organic products, changes in the droplet hygroscopicity, and optical properties. Exposure of the aqueous droplets to ozone leads to the formation of products with a wide range of volatilities spanning from involatile to volatile. Reactive uptake coefficients show a weak dependence on ozone concentration, but no dependence on RH or salt concentration. The time evolving RI depends significantly on the RH at which the oxidation proceeds and can even show opposing trends; while the RI increases with ozone exposure at low relative humidity, the RI decreases when the oxidation proceeds at high relative humidity. The variations in RI are broadly consistent with a framework for predicting RIs for organic components published by Cappa et al. (J. Geophys. Res. 2011, 116, D15204). Once oxidized, particles are shown to form amorphous phases on drying rather than crystallization, with slow evaporation kinetics of residual water.