Year-round modeling of sulfate aerosol over Asia through updates of aqueous-phase oxidation and gas-phase reactions with stabilized Criegee intermediates
Year-round modeling of sulfate aerosol over Asia through updates of aqueous-phase oxidation and gas-phase reactions with stabilized Criegee intermediates
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DOI：
10.1016/j.aeaoa.2021.100123
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发表时间：
2021-09-06
影响因子：
4.6
通讯作者：
Chatani, Satoru
中科院分区：
文献类型：
--
作者：
Itahashi, Syuichi;Uchida, Risa;Chatani, Satoru
硫酸盐气溶胶（SO 42-）是亚洲国家颗粒物的主要成分。精确的数值模拟对于旨在降低SO 42-浓度的适当政策制定非常重要。SO 42-的模拟性能上级气溶胶组分，然而，目前的模式低估了亚洲冬季的SO（4）（2-）浓度。以往的研究提出了一个异质过程的冬季灰霾事件，但这些类型的研究是有限的空间和时间，因为他们只覆盖中国大陆的冬季。在气溶胶浓度远低于中国的其他地区也有低估的报告。在这项研究中，水和气相氧化过程中，目前的建模进行了重新考虑，并在亚洲使用全年模拟评估其作用。改进了现有的以Fe和Mn为催化剂的水解酶氧化O-2的方法，并考虑到亚洲地区大气中性化的特点，增加了以NO2为催化剂的氧化方法。对于气相氧化，引入了三种稳定的Criegee中间体（SCIs;甲醛氧化物（CH 2 OO）、乙醛氧化物（CH 3CHOO）和丙醛氧化物（（CH 3）（2）COO））。考虑到CH 2 OO与水反应的不确定性，采用了速率常数的上下限。更新的氧化过程导致模拟的SO 42-浓度增加。在亚洲冬季，模式的性能得到了有效的改善，并在其他季节的模式性能没有降低更新。偏差的改善约为3%，在冬季，而偏差的恶化是在1%以内，在春季至夏季和秋季的2%，当使用的CH 2 OO速率常数的下限与水。SCIs的作用强烈依赖于CH 2 OO与水反应的速率常数。SCIs的模拟浓度与估计水平一致，CH 2 OO与水的速率常数的下限符合SCIs的估计浓度水平。SCIs可能在亚洲冬季SO 42-的产生中起重要作用，特别是在中国的下风向区域。本研究中采用的方法也有可能提高其他地区的建模性能。
Sulfate aerosol (SO42-) is a main component of particulate matter in Asian countries. Accurate numerical modeling is important for appropriate policy-making aimed at reducing SO42- concentrations. The modeling performance for SO42- is superior among aerosol components, however, current models underestimate SO(4)(2- )concentrations during winter over Asia. Previous studies have proposed a heterogeneous process for winter haze events, but these kinds of studies are limited spatially and temporally because they cover only mainland China in winter. Underestimation has also been reported in other regions where the aerosol concentration is much lower than in China. In this study, the aqueous- and gas-phase oxidation processes in the current modeling were reconsidered, and their roles were evaluated over Asia using a year-round simulation. The existing aqueousphase oxidation of O-2 with Fe and Mn as catalysts was refined, and oxidation with NO2 was added due to the neutralized atmosphere over Asia. For gas-phase oxidation, three stabilized Criegee intermediates (SCIs; formaldehyde oxide (CH2OO), acetaldehyde oxide (CH3CHOO), and propionaldehyde oxide ((CH3)(2)COO)) were introduced. Considering the uncertainty of the reaction of CH2OO with water, the upper and lower limits of the rate constant were applied. The updated oxidation processes led to an increase in the modeled SO42- concentration. The model performance over Asia in winter was effectively improved, and the updates did not degrade the model performance in other seasons. The improvements in biases were approximately 3% during winter, whereas the deterioration in biases were within 1% in spring to summer and 2% in autumn, when the lower limit of the CH2OO rate constant with water was used. The role of SCIs depended strongly on the rate constants of the reaction of CH2OO with water. The simulated concentration of SCIs agreed well with the estimated levels, and the lower limit of the rate constant of CH2OO with water fitted within the estimated SCIs concentration levels. SCIs may play an important role in SO42- production over Asia in winter, especially the downwind region of China. The approach taken in this study has the potential to improve modeling performance in other regions as well.