Influence of particle viscosity on mass transfer and heterogeneous ozonolysis kinetics in aqueous-sucrose-maleic acid aerosol.
Influence of particle viscosity on mass transfer and heterogeneous ozonolysis kinetics in aqueous-sucrose-maleic acid aerosol.
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DOI：
10.1039/c8cp01666f
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发表时间：
2018-06
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影响因子：
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通讯作者：
Frances H. Marshall;T. Berkemeier;M. Shiraiwa;L. Nandy;Peter B. Ohm;C. Dutcher;J. Reid
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文献类型：
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作者：
Frances H. Marshall;T. Berkemeier;M. Shiraiwa;L. Nandy;Peter B. Ohm;C. Dutcher;J. Reid
气溶胶中气相和凝聚相之间的质量传递可能受到粘性颗粒内缓慢的整体扩散的限制。在粘性有机气溶胶颗粒的非均相和多相反应过程中，有必要考虑许多传质过程的相互作用以及它们如何受到粘度的影响，包括半挥发性有机反应物、水和氧化剂的分配动力学。为了约束非均相化学的动力学模型，测量必须提供尽可能多的可观测信息。在这里，臭氧分解的马来酸（MA）在三元气溶胶颗粒含有水和蔗糖被用作一个模型系统。通过改变蔗糖与MA的质量比并通过在宽范围的相对湿度下进行反应，直接测量表明颗粒的粘度可以变化超过7个数量级。MA的挥发动力学的测量表明，该粘度范围导致MA的有效蒸气压的抑制为3-4个数量级。MA在颗粒相中的扩散系数的推断值紧密地反映了从Stokes-Einstein方程和粘度的变化中的扩散系数的预期变化。臭氧分解的动力学表现出类似的颗粒粘度的依赖性，可以进一步研究使用的动力学多层模型的气溶胶表面和本体化学（KM-CHR）。两种情况下，一个约束MA的扩散系数的斯托克斯-爱因斯坦方程和其他包括扩散系数作为拟合参数的基础上预期的，产生类似的臭氧分解动力学的充分表示，推断从实验衰减的乙烯基C-H伸缩振动的MA的签名。然而，这两种情况下提供了非常不同的参数化的成分依赖性的臭氧的扩散系数内的凝聚相，产生定性不同的时间依赖性的内部浓度分布。我们建议，这突出了提供额外的实验观测值（如颗粒大小，组成的异质性）的重要性，如果测量和模型是普遍协调。
Mass transfer between the gas and condensed phases in aerosols can be limited by slow bulk diffusion within viscous particles. During the heterogeneous and multiphase reactions of viscous organic aerosol particles, it is necessary to consider the interplay of numerous mass transfer processes and how they are impacted by viscosity, including the partitioning kinetics of semi-volatile organic reactants, water and oxidants. To constrain kinetic models of the heterogeneous chemistry, measurements must provide information on as many observables as possible. Here, the ozonolysis of maleic acid (MA) in ternary aerosol particles containing water and sucrose is used as a model system. By varying the mass ratio of sucrose to MA and by performing reactions over a wide range of relative humidity, direct measurements show that the viscosity of the particle can be varied over 7 orders of magnitude. Measurements of the volatilisation kinetics of MA show that this range in viscosity leads to a suppression in the effective vapour pressure of MA of 3-4 orders of magnitude. The inferred values of the diffusion coefficient of MA in the particle phase closely mirror the expected change in diffusion coefficient from the Stokes-Einstein equation and the change in viscosity. The kinetics of ozonolysis show a similar dependence on particle viscosity that can be further investigated using the kinetic multi-layer model of aerosol surface and bulk chemistry (KM-SUB). Two scenarios, one constraining the diffusion coefficients for MA to those expected based on the Stokes-Einstein equation and the other including the diffusion coefficients as a fit parameter, yield similarly adequate representations of the ozonolysis kinetics, as inferred from the experimental decay in the signature of the vinylic C-H stretching vibration of MA. However, these two scenarios provide very different parameterisations of the compositional dependence of the diffusion coefficients of ozone within the condensed phase, yielding qualitatively different time-dependent internal concentration profiles. We suggest that this highlights the importance of providing additional experimental observables (e.g. particle size, heterogeneity in composition) if measurements and models are to be universally reconciled.