Nitrate Photolysis in Mixed Sucrose-Nitrate-Sulfate Particles at Different Relative Humidities
Nitrate Photolysis in Mixed Sucrose-Nitrate-Sulfate Particles at Different Relative Humidities
复制标题
不同相对湿度下混合蔗糖-硝酸盐-硫酸盐颗粒中硝酸盐的光解
DOI：
10.1021/acs.jpca.1c00669
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发表时间：
2021
影响因子：
2.9
通讯作者：
Chan Chak K.
中科院分区：
文献类型：
--
作者：
Liang Zhancong;Zhang Ruifeng;Gen Masao;Chu Yangxi;Chan Chak K.
大气颗粒可能是粘性的。扩散的限制阻碍了氧化剂从气相到颗粒相的传质，并阻碍了多相氧化过程。另一方面，已经发现硝酸盐光解在颗粒内产生氧化剂如OH自由基方面是有效的。硝酸盐的光解是否可以有效地在粘性颗粒中进行，以及它如何影响颗粒的物理化学性质还没有太多的探索。在这项研究中，我们研究了颗粒硝酸盐光解混合蔗糖-硝酸盐-硫酸盐颗粒作为大气中含有有机和无机成分的粘性颗粒作为相对湿度（RH）和蔗糖的摩尔分数的函数的替代物的总溶质（FSU）与原位显微拉曼系统。蔗糖抑制硝酸盐结晶，和高的光解速率常数（10-5s-1）被发现，无论相对湿度。对于FSU = 0.5和0.33的颗粒在30%RH下辐照，我们观察到从液滴到形成包裹体，然后可能是“中空”半固体颗粒的形态变化，其在中心位置没有显示拉曼信号。结合无机物的半峰全宽（FWHM）、具有凸起表面的图像以及光学显微成像中颗粒尺寸的增加所指示的相态，我们推断气体产物的受阻扩散（即，氮氧化物（NOx，NOy）的硝酸盐光解是一个可能的原因的形态变化。这些结果的大气影响。
Atmospheric particles can be viscous. The limitation in diffusion impedes the mass transfer of oxidants from the gas phase to the particle phase and hinders multiphase oxidation processes. On the other hand, nitrate photolysis has been found to be effective in producing oxidants such as OH radicals within the particles. Whether nitrate photolysis can effectively proceed in viscous particles and how it may affect the physicochemical properties of the particle have not been much explored. In this study, we investigated particulate nitrate photolysis in mixed sucrose–nitrate–sulfate particles as surrogates of atmospheric viscous particles containing organic and inorganic components as a function of relative humidity (RH) and the molar fraction of sucrose to the total solute (FSU) with an in situ micro-Raman system. Sucrose suppressed nitrate crystallization, and high photolysis rate constants (∼10–5s–1) were found, irrespective of the RH. ForFSU= 0.5 and 0.33 particles under irradiation at 30% RH, we observed morphological changes from droplets to the formation of inclusions and then likely “hollow” semisolid particles, which did not show Raman signal at central locations. Together with the phase states of inorganics indicated by the full width at half-maxima (FWHM), images with bulged surfaces, and size increase of the particles in optical microscopic imaging, we inferred that the hindered diffusion of gaseous products (i.e., NOx, NOy) from nitrate photolysis is a likely reason for the morphological changes. Atmospheric implications of these results are also presented.