Secondary aerosol formation from dimethyl sulfide - improved mechanistic understanding based on smog chamber experiments and modelling
Secondary aerosol formation from dimethyl sulfide - improved mechanistic understanding based on smog chamber experiments and modelling
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DOI：
10.5194/acp-21-9955-2021
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发表时间：
2021-07-02
影响因子：
6.3
通讯作者：
Roldin, Pontus
中科院分区：
文献类型：
--
作者：
de Jonge, Robin Wollesen;Elm, Jonas;Roldin, Pontus
二甲基硫(DMS)是海洋大气中主要的生物硫化物。DMS氧化产生的低挥发性酸促进硫气溶胶的形成和增长，并最终改变云的性质和地球的气候。我们在奥胡斯大学利用气溶胶动力学和气固两相化学动力学多层模型ADCHAM研究了DMS的OH引发氧化反应。我们的工作包括开发一个修订的和全面的多相DMS氧化机理，能够再现雾霾室内和大气相关条件。AURA小室中的二次气溶胶质量产率强烈依赖于甲基亚磺酸(MSIA)和OH的反应，导致在低相对湿度(RH)下总PM增加82.8%，而中间自由基CH3SCH_2OO在高温和RH时自氧化生成羟基硫代甲酸甲酯(HPMTF)，使总PM减少55.8%。观察和模拟结果有力地支持了这一发现，即在密封袋的特氟龙表面存在一层液膜，它增加了水溶性中间体和氧化剂二甲基亚砜(DMSO)、MSIA、HPMTF、SO2、甲烷磺酸(MSA)、硫酸(SA)和过氧化氢的壁面损失。这一影响使干燥(0%RH-12%RH)和潮湿(50%RH-80%RH)条件下的二次气溶胶质量产率分别下降了64.8%和91.7%。模拟海洋大气的运行表明，OH在MBL中包含较强的DMS汇(占DMS总汇通量的31.1%)，但不如卤素物种Cl和BrO的综合影响(分别占24.3%和38.7%)。多云条件促进了气相中积累的SO2生成SO42比质量(PM)，而无云期则有利于潮解颗粒中MSA的形成。水相化学的排除降低了DMS的下沉，因为海雾粒子中没有卤素被激活，并且由于忽略了粒子相中SO42-和MSA PM的产生而低估了二次气溶胶的质量产率。总体而言，这项研究表明，目前文献中报道的DMS氧化机制不足以重现在光晕室中获得的结果，而修订的化学物质很好地捕捉到了形成的气溶胶颗粒的形成、生长和化学成分。此外，我们强调了在低海洋喷雾排放的条件下，在周围海洋大气中由OH引发的DMS氧化的重要性。
Dimethyl sulfide (DMS) is the dominant biogenic sulfur compound in the ambient marine atmosphere. Low-volatility acids from DMS oxidation promote the formation and growth of sulfur aerosols and ultimately alter cloud properties and Earth's climate. We studied the OH-initiated oxidation of DMS in the Aarhus University Research on Aerosol (AURA) smog chamber and the marine boundary layer (MBL) with the aerosol dynamics and gas- and particle-phase chemistry kinetic multilayer model ADCHAM. Our work involved the development of a revised and comprehensive multiphase DMS oxidation mechanism, capable of both reproducing smog chamber and atmospheric relevant conditions. The secondary aerosol mass yield in the AURA chamber was found to have a strong dependence on the reaction of methyl sulfinic acid (MSIA) and OH, causing a 82.8 % increase in the total PM at low relative humidity (RH), while the autoxidation of the intermediate radical CH3SCH2OO forming hydroperoxymethyl thioformate (HPMTF) proved important at high temperature and RH, decreasing the total PM by 55.8 %. The observations and modelling strongly support the finding that a liquid water film existed on the Teflon surface of the chamber bag, which enhanced the wall loss of water-soluble intermediates and oxidants dimethyl sulfoxide (DMSO), MSIA, HPMTF, SO2, methanesulfonic acid (MSA), sulfuric acid (SA) and H2O2. The effect caused a 64.8 % and 91.7 % decrease in the secondary aerosol mass yield obtained at both dry (0 % RH-12 % RH) and humid (50 % RH-80 % RH) conditions, respectively. Model runs reproducing the ambient marine atmosphere indicate that OH comprises a strong sink of DMS in the MBL (accounting for 31.1 % of the total sink flux of DMS) although less important than the combined effect of halogen species Cl and BrO (accounting for 24.3 % and 38.7 %, respectively). Cloudy conditions promote the production of SO42- particular mass (PM) from SO2 accumulated in the gas phase, while cloud-free periods facilitate MSA formation in the deliquesced particles. The exclusion of aqueous-phase chemistry lowers the DMS sink as no halogens are activated in the sea spray particles and underestimates the secondary aerosol mass yield by neglecting SO42- and MSA PM production in the particle phase. Overall, this study demonstrated that the current DMS oxidation mechanisms reported in literature are inadequate in reproducing the results obtained in the AURA chamber, whereas the revised chemistry captured the formation, growth and chemical composition of the formed aerosol particles well. Furthermore, we emphasize the importance of OH-initiated oxidation of DMS in the ambient marine atmosphere during conditions with low sea spray emissions.