State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.
College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 100049, China.
Sci Rep. 2017 Jul 3;7(1):4550. doi: 10.1038/s41598-017-04551-6.
Manganese oxides from anthropogenic sources can promote the formation of sulfate through catalytic oxidation of SO. In this study, the kinetics of SO reactions on MnO with different morphologies (α, β, γ and δ) was investigated using flow tube reactor and in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). Under dry conditions, the reactivity towards SO uptake was highest on δ-MnO but lowest on β-MnO, with a geometric uptake coefficient (γ) of (2.42 ± 0.13) ×10 and a corrected uptake coefficient (γ) of (1.48 ± 0.21) ×10 for the former while γ of (3.35 ± 0.43) ×10 and γ of (7.46 ± 2.97) ×10 for the latter. Under wet conditions, the presence of water altered the chemical form of sulfate and was in favor for the heterogeneous oxidation of SO. The maximum sulfate formation rate was reached at 25% RH and 45% for δ-MnO and γ-MnO, respectively, possibly due to their different crystal structures. The results suggest that morphologies and RH are important factors influencing the heterogeneous reaction of SO on mineral aerosols, and that aqueous oxidation process involving transition metals of Mn might be a potential important pathway for SO oxidation in the atmosphere.
人为来源的氧化锰可以通过催化氧化 SO 来促进硫酸盐的形成。在这项研究中，使用流动管反应器和原位漫反射红外傅里叶变换光谱（DRIFTS）研究了不同形态（α、β、γ和δ）的 MnO 对 SO 反应的动力学。在干燥条件下，δ-MnO 对 SO 吸收的反应性最高，但β-MnO 最低，前者的几何吸收系数（γ）为（2.42±0.13）×10，校正后的吸收系数（γ）为（1.48±0.21）×10，而后者的γ为（3.35±0.43）×10和γ为（7.46±2.97）×10。在湿条件下，水的存在改变了硫酸盐的化学形态，有利于 SO 的非均相氧化。在 25% RH 和 45%下，δ-MnO 和 γ-MnO 分别达到最大硫酸盐生成速率，这可能是由于它们不同的晶体结构。结果表明，形态和 RH 是影响矿物气溶胶中 SO 非均相反应的重要因素，涉及 Mn 过渡金属的水相氧化过程可能是大气中 SO 氧化的一个潜在重要途径。
