论文标题
抗坏血酸的离子强度和pH依赖性反应性朝着由气溶胶光学镊子研究的水性微滴体中的臭氧
Ionic-strength and pH dependent reactivities of ascorbic acid toward ozone in aqueous micro-droplets studied by aerosol optical tweezers
论文作者
论文摘要
在这项研究中研究了使用带有拉曼光谱的气溶胶光学镊子的单一抗坏血酸（AH $ _2 $）气溶胶颗粒与气相臭氧的异质氧化反应。 AH $ _2 $ _2 $ + o $ _3 $反应的测得的液相双分子速率系数具有显着的pH依赖性，并且离子强度0.2 m的相应值为$（3.1 \ pm 2.0）\ times 10^5 $ m $ m $ m $^{ - 1} { - 1} m $^{ - 1} $ s $^{ - 1} $分别为ph $ \ $ 2和6。这些在微米大小的液滴中测量的结果与以前的大量测量值一致，表明观察到的气溶胶反应动力学可以完全通过液相扩散和AH $ _2 $ + o $ _3 $反应来解释。此外，结果表明，高离子强度可以增强AH $ _2 $ + o $ $ _3 $反应的液相速率系数。该结果还表现出负臭氧压力依赖性，可以根据langmuir-hinshelwood类型的机制合理化，用于通过气相臭氧的AH $ _2 $ eerosol颗粒的异质氧化。本工作的结果表明，在酸化的气道液体中，AH $ _2 $对大气臭氧的抗氧化能力将得到显着抑制。
The heterogeneous oxidation reaction of single aqueous ascorbic acid (AH$_2$) aerosol particles with gas-phase ozone was investigated in this study utilizing aerosol optical tweezers with Raman spectroscopy. The measured liquid-phase bimolecular rate coefficients of the AH$_2$ + O$_3$ reaction exhibit a significant pH dependence, and the corresponding values at ionic strength 0.2 M are $(3.1 \pm 2.0) \times 10^5$ M$^{-1}$s$^{-1}$ and $(1.2 \pm 0.6) \times 10^7$ M$^{-1}$s$^{-1}$ for pH $\approx$ 2 and 6, respectively. These results measured in micron-sized droplets agree with those from previous bulk measurements, indicating that the observed aerosol reaction kinetics can be solely explained by liquid phase diffusion and AH$_2$ + O$_3$ reaction. Furthermore, the results indicate that high ionic strengths could enhance the liquid-phase rate coefficients of the AH$_2$ + O$_3$ reaction. The results also exhibit a negative ozone pressure dependence that can be rationalized in terms of a Langmuir-Hinshelwood type mechanism for the heterogeneous oxidation of AH$_2$ aerosol particles by gas-phase ozone. The results of the present work imply that in acidified airway-lining fluids the antioxidant ability of AH$_2$ against atmospheric ozone will be significantly suppressed.
