Extension of a gaseous dry deposition algorithm to oxidized volatile organic compounds and hydrogen cyanide for application in chemistry transport models.
Extension of a gaseous dry deposition algorithm to oxidized volatile organic compounds and hydrogen cyanide for application in chemistry transport models.
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DOI：
10.5194/gmd-14-5093-2021
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发表时间：
2021-08-16
影响因子：
6.8
通讯作者：
Wang X
中科院分区：
文献类型：
--
作者：
Wu Z;Zhang L;Walker JT;Makar PA;Perlinger JA;Wang X
干沉降过程是指由于地球表面（包括植被、下层土壤和任何其他表面类型）吸收污染物而造成的大气污染物通量损失。在化学输运模型 (CTM) 中，化学物质的干沉积通量通常计算为其表面层浓度与其干沉积速度 (Vd) 的乘积；后者是一个需要高度经验参数化的变量，因为影响这一过程的气象、生物和化学因素太多。气态干沉积方案参数化了 31 种无机和有机气态物质的 Vd。本研究扩展了该方案，在保留原始模型结构和公式的同时，添加了额外的 12 种氧化挥发性有机化合物（oVOC）和氰化氢（HCN），以满足日益复杂的 CTM 的需求。这些附加化学物质的模型参数是根据其物理化学性质（即有效亨利定律常数和氧化能力）凭经验选择的。将模拟的 Vd 值与 2013 年 6 月美国东南部混交林的现场通量测量值进行比较。该模型捕获了观测到的 Vd 昼夜循环的基本特征。模拟的 Vd 值与大多数 oVOC 在夜间的测量值相当。然而，白天模拟的 Vd 值大多在 1 cm s−1 左右，这比观测到的白天最大值 2-5 cm s−1 小得多。对各个阻力项和吸收途径的分析表明，由于树冠附近快速大气化学反应造成的通量发散可能是白天模型测量值出现较大差异的主要原因。扩展的干沉积方案可能为许多 oVOC 提供保守的 Vd 值。虽然可以通过将关键大气化学过程耦合到干沉积方案中来模拟更高的 Vd 值和双向通量，但我们建议需要在其他地点获得高 oVOC Vd 值的更多实验证据，以确认此处研究的高值的更广泛适用性。导致高测量 oVOC Vd 值的基本过程需要进一步研究。
The dry deposition process refers to flux loss of an atmospheric pollutant due to uptake of the pollutant by the Earth’s surfaces, including vegetation, underlying soil, and any other surface types. In chemistry transport models (CTMs), the dry deposition flux of a chemical species is typically calculated as the product of its surface layer concentration and its dry deposition velocity (Vd); the latter is a variable that needs to be highly empirically parameterized due to too many meteorological, biological, and chemical factors affecting this process. The gaseous dry deposition scheme of parameterizes Vd for 31 inorganic and organic gaseous species. The present study extends the scheme of to include an additional 12 oxidized volatile organic compounds (oVOCs) and hydrogen cyanide (HCN), while keeping the original model structure and formulas, to meet the demand of CTMs with increasing complexity. Model parameters for these additional chemical species are empirically chosen based on their physicochemical properties, namely the effective Henry’s law constants and oxidizing capacities. Modeled Vd values are compared against field flux measurements over a mixed forest in the southeastern US during June 2013. The model captures the basic features of the diel cycles of the observed Vd. Modeled Vd values are comparable to the measurements for most of the oVOCs at night. However, modeled Vd values are mostly around 1 cm s−1 during daytime, which is much smaller than the observed daytime maxima of 2–5 cm s−1. Analysis of the individual resistance terms and uptake pathways suggests that flux divergence due to fast atmospheric chemical reactions near the canopy was likely the main cause of the large model–measurement discrepancies during daytime. The extended dry deposition scheme likely provides conservative Vd values for many oVOCs. While higher Vd values and bidirectional fluxes can be simulated by coupling key atmospheric chemical processes into the dry deposition scheme, we suggest that more experimental evidence of high oVOC Vd values at additional sites is required to confirm the broader applicability of the high values studied here. The underlying processes leading to high measured oVOC Vd values require further investigation.
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