Relative Humidity Changes the Role of SO2 in Biogenic Secondary Organic Aerosol Formation,The Journal of Physical Chemistry Letters

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Relative Humidity Changes the Role of SO2 in Biogenic Secondary Organic Aerosol Formation
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2021-07-29 , DOI: 10.1021/acs.jpclett.1c01550
Li Xu ₁ , Narcisse T Tsona ₁ , Lin Du ₁

Affiliation

SO₂ influences secondary organic aerosol (SOA) and organosulfates (OSs) formation but mechanisms remain elusive. This study focuses on this topic by investigating biogenic γ-terpinene ozonolysis under various SO₂ and relative humidity (RH) conditions. With a constant SO₂ concentration (∼110 ppb), the increase in RH transformed SO₂ sinks from stabilized Criegee intermediates (sCIs) to peroxides in aerosol particles. The associated changes in particle acidity and liquid water content may collectively first lead to decreased and then increased SOA yield with increasing RH, with the turning point appearing at ∼30% RH. The abundance of most OSs formed under 45% RH was more than 5 times higher than that of OSs formed under 10% RH, possibly due to interactions of dissolved SO₂ with hydroperoxides (ROOH) in SOA. ROOHs formed from the autoxidation processes of alkylperoxy radicals were proposed to be precursors for highly oxidized OSs (HOOSs) that decreased SOA volatility and showed a certain abundance in ambient aerosols. This study highlights that high RH potentially enhances the contribution of SO₂ to OSs formation, and particularly, HOOSs formation during monoterpene ozonolysis in the atmosphere.

中文翻译：

相对湿度改变 SO2 在生物二次有机气溶胶形成中的作用

SO ₂影响二次有机气溶胶 (SOA) 和有机硫酸盐 (OS) 的形成，但机制仍然难以捉摸。本研究通过研究各种 SO ₂和相对湿度 (RH) 条件下的生物源 γ-萜品烯臭氧分解来关注这一主题。在 SO ₂浓度恒定(~110 ppb) 的情况下，RH 的增加转化了 SO ₂从稳定的 Criegee 中间体 (sCI) 汇入气溶胶颗粒中的过氧化物。随着相对湿度的增加，颗粒酸度和液态水含量的相关变化可能首先导致 SOA 产量降低，然后增加，转折点出现在~30% RH。大多数在 45% RH 下形成的 OSs 的丰度比在 10% RH 下形成的 OSs 高 5 倍以上，这可能是由于溶解的 SO ₂与 SOA 中氢过氧化物 (ROOH) 的相互作用。由烷基过氧自由基的自氧化过程形成的 ROOH 被认为是高度氧化的 OS (HOOS) 的前体，可降低 SOA 的挥发性并在环境气溶胶中显示出一定的丰度。该研究强调，高 RH 可能会增强 SO ₂的贡献 OSs 的形成，特别是大气中单萜臭氧分解过程中 HOOSs 的形成。

更新日期：2021-08-06

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