Modeling the OH-Initiated Oxidation of Mercury in the Global Atmosphere without Violating Physical Laws
Modeling the OH-Initiated Oxidation of Mercury in the Global Atmosphere without Violating Physical Laws
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DOI：
10.1021/acs.jpca.9b10121
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发表时间：
2020-01-16
影响因子：
2.9
通讯作者：
Jacob, Daniel J.
中科院分区：
文献类型：
--
作者：
Dibble, Theodore S.;Tetu, Hanna L.;Jacob, Daniel J.
2005年，Calvert和Lindberg（Calvert，J.G.; Lindberg，S. E.大气。Environ. 2005，39，3355-3367）写道，使用实验室得出的OH + Hg（0）“的速率常数。确定对流层中OH去除汞的程度将大大高估该反应去除汞的重要性。“由OH + Hg形成的HOHg中心点中间体在反应之前大多会在大气中分解。相比之下，在实验室实验中，卡尔弗特和林德伯格预计HOHg中心点与自由基（其浓度远高于大气中的浓度）反应。然而，几乎所有的汞（0）氧化模型都忽略了卡尔弗特和林德伯格的论点。我们提出了一种建模方法，包括OH +汞反应，同时定量占HOHg中心点的解离。我们使用高水平的量子化学建立HO-Hg键能为11.0千卡/摩尔，并计算OH + Hg = HOHg中心点的平衡常数。使用测得的速率常数与汞的OH的协会，我们确定HOHg中心点解离的速率常数。理论也被用来证明HOHg中心点形成稳定的化合物，HOHgY，与大气自由基（Y = NO2，HOO中心点，CH 3 OO中心点，和BrO）。然后，我们提出了用于建模OH引发的Hg（0）氧化的速率常数。我们使用这种机制来模拟2013-2015年期间全球Hg（0）的氧化，使用GEOS-Chem大气化学3D模型。由于HOHg中心点的快速解离，
In 2005, Calvert and Lindberg (Calvert, J. G.; Lindberg, S. E. Atmos. Environ. 2005, 39, 3355-3367) wrote that the use of laboratory-derived rate constants for OH + Hg(0) "...to determine the extent of Hg removal by OH in the troposphere will greatly overestimate the importance of Hg removal by this reaction." The HOHg center dot intermediate formed from OH + Hg will mostly fall apart in the atmosphere before it can react. By contrast, in laboratory experiments, Calvert and Lindberg expected HOHg center dot to react with radicals (whose concentrations are much higher than in the atmosphere). Yet, almost all models of oxidation of Hg(0) ignore the argument of Calvert and Lindberg. We present a way for modelers to include the OH + Hg reaction while accounting quantitatively for the dissociation of HOHg center dot. We use high levels of quantum chemistry to establish the HO-Hg bond energy as 11.0 kcal/mol and calculate the equilibrium constant for OH + Hg = HOHg center dot. Using the measured rate constant for the association of OH with Hg, we determine the rate constant for HOHg center dot dissociation. Theory is also used to demonstrate that HOHg center dot forms stable compounds, HOHgY, with atmospheric radicals (Y = NO2, HOO center dot, CH3OO center dot, and BrO). We then present rate constants for use in modeling OH-initiated oxidation of Hg(0). We use this mechanism to model the global oxidation of Hg(0) in the period 2013-2015 using the GEOS-Chem 3D model of atmospheric chemistry. Because of the rapid dissociation of HOHg center dot, OH accounts for