A neglected pathway for the accretion products formation in the atmosphere
A neglected pathway for the accretion products formation in the atmosphere
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大气中吸积产物形成的被忽视的途径
DOI：
10.1016/j.scitotenv.2022.157494
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发表时间：
2022
影响因子：
9.8
通讯作者：
Jiemin Cheng
中科院分区：
文献类型：
--
作者：
Xiangli Shi;Ruoyu Tang;Zuokang Dong;Houfeng Liu;Fei Xu;Qingzhu Zhang;Wansong Zong;Jiemin Cheng
羟基自由基引发α-蒎烯自氧化形成的高氧有机分子（HOM）在新颗粒的形成中起着重要作用。认为由过氧自由基的自反应和交叉反应（RO 2 + R´O 2反应）形成的吸积产物ROOR´具有极低的挥发性，更容易参与成核。然而，ROOR的形成机理尚未得到实验或理论计算的充分证明。本文提出了一种新的RO 2与α-蒎烯反应机理（RO 2 + α-蒎烯反应），该反应具有比RO 2与R´O 2反应更低的势垒和更大的速率常数，这解释了质谱实验中发现的ROOR´的形成。ro2与α-蒎烯反应产生的ROOR可以通过自氧化链生成具有较高氧碳比（O/C）的hom二聚体和三聚体。我们还证明了NO x和ho2自由基的存在会降低ro2浓度，但不能完全抑制HOM单体和ROOR´的形成。即使一个或两个自由基都是酰基过氧自由基（RC(O)O 2）， RC(O)O 2与α-蒎烯（RC(O)O 2 + α-蒎烯反应）反应的势垒也低于与RC(O)O 2 （RO 2 + RC(O)O 2反应）或RC(O)O 2自身反应(RC（O)O 2 + RC(O)O 2反应）。本研究首次揭示了大气中ro2 /RC(O) o2与α-蒎烯反应的机理，为研究大气化学中作为SOA前体的吸积产物提供了新的思路。•研究了HOM二聚体的形成机理。•RO 2 + R´O 2反应的势垒非常高。•ro2自由基与α-蒎烯反应生成吸积产物的作用不容忽视。•NO x抑制RO 2的自氧化，导致增积产物的产量降低。
Highly oxygenated organic molecules (HOM) formed by the autoxidation of α-pinene initiated by OH radicals play an important role in new particle formation. It is believed that the accretion products, ROOR´, formed by the self- and cross-reaction of peroxy radicals (RO 2 + R´O 2 reactions), have extremely low volatility and are more likely to participate in nucleation. However, the mechanism of ROOR´ formation has not been fully demonstrated by experiment or theoretical calculation. Herein, we propose a novel mechanism of RO 2 reacting with α-pinene (RO 2 + α-pinene reactions) that have much lower potential barriers and larger rate constants than the reaction of RO 2 with R´O 2 , which explains the ROOR´ formation found in the mass spectrometry experiments. The ROOR´ resulting from the reaction of RO 2 with α-pinene can produce HOM dimers and trimers with a higher oxygen-to‑carbon (O/C) ratio through a autoxidation chain. We also demonstrated that the presence of NO x and HO 2 radical will reduce the RO 2 concentration, but cannot completely inhibit the formation of HOM monomers and ROOR´. Even if one or both of RO 2 radicals are acyl peroxy radicals (RC(O)O 2 ), the potential barriers of the reactions between RC(O)O 2 and α-pinene (RC(O)O 2 + α-pinene reactions) are lower than that of RO 2 reacting with RC(O)O 2 (RO 2 + RC(O)O 2 reactions) or RC(O)O 2 self-reactions (RC(O)O 2 + RC(O)O 2 reactions). The current work revealed, for the first time, a mechanism of RO 2 /RC(O)O 2 reacting with α-pinene in the atmosphere, which provides new insight into the atmospheric chemistry of accretion products as SOA precursors. • The formation mechanisms of HOM dimers were investigated. • The potential barriers of RO 2 + R´O 2 reactions are extremely high. • RO 2 radical reacting with α-pinene to form accretion products is not negligible. • NO x inhibits the autoxidation of RO 2 leading to a lower yield of accretion products.