Simulation of organic aerosol formation during the CalNex study: updated mobile emissions and secondary organic aerosol parameterization for intermediate-volatility organic compounds.
Simulation of organic aerosol formation during the CalNex study: updated mobile emissions and secondary organic aerosol parameterization for intermediate-volatility organic compounds.
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CalNex 研究期间有机气溶胶形成的模拟：更新了中等挥发性有机化合物的移动排放和二次有机气溶胶参数化。
DOI：
10.5194/acp-20-4313-2020
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发表时间：
2020
影响因子：
6.3
通讯作者：
A. Robinson
中科院分区：
文献类型：
--
作者：
Quanyang Lu;B. Murphy;Momei Qin;P. Adams;Yunliang Zhao;H. Pye;C. Efstathiou;Chris Allen;A. Robinson
我们描述了使用社区多尺度空气质量模型5.3版本（CMAQ v5.3）的更新版本的模拟，以调查在CalNex研究期间南加州中等挥发性有机化合物（IVOCs）对二次有机气溶胶（SOA）形成的贡献。我们首先从移动源的IVOC排放中获得SOA形成的模型就绪参数化。为了解释柴油和汽油源的SOA形成，参数化有六个集总前体物质，可以解决挥发性和分子结构（芳香族与脂肪族）。我们还实施了新的移动源排放概况，根据直接测量对所有IVOCs进行量化。这些配置文件已在SPECIATE 5.0中发布。通过结合半挥发性有机化合物（SVOCs）和IVOCs的综合移动源排放曲线和实验约束的SOA产量，该CMAQ配置最能代表移动源对城市和区域环境有机气溶胶（OA）的贡献。在洛杉矶地区，汽油源排放的非甲烷有机气体（nmog）是柴油源的4倍，但柴油源排放的IVOCs在绝对基础上大约是3倍。修正后的模型预测，所有移动源（包括公路上和非公路上的汽油、飞机和公路上和非公路上的柴油）对帕萨迪纳市SOA日峰值浓度的贡献约为1 μgm-3。这表示与CMAQ的基础版本相比，预测的每日峰值SOA形成量增加了约70%。因此，移动源排放中的IVOCs贡献的SOA几乎与传统前体（如单环芳烃）一样多。然而，在CMAQ中计算这些排放并不能再现环境SOA或IVOCs的测量结果。为了研究其他挥发性有机化合物源的潜在贡献，我们对来自非移动源的不同数量的挥发性有机化合物排放进行了两次探索性模拟。为了接近主要碳氢化合物IVOC的质量平衡，IVOC需要占非移动源NMOG排放量的12%（或相当于洛杉矶-帕萨迪纳地区的30.7 t d-1），这个值完全在挥发性化学产品IVOC含量的报告范围内。为了接近SOA质量平衡，并解释帕萨迪纳市轻度含氧IVOCs，非移动源NMOG排放的额外14.8%需要是IVOCs（假设移动IVOCs的SOA产量适用于非移动IVOCs）。然而，对于非移动源，ivoc与nmog的比值为26.8%（相当于洛杉矶-帕萨迪纳地区的68.5吨d-1），这可能是不切实际的高。我们的研究结果强调了IVOCs对洛杉矶地区SOA生产的重要贡献，但强调了必须解决其他不确定性（多代老化、水化学和蒸汽壁损失）以关闭SOA质量平衡。这项研究还强调了减少移动源排放的法规的有效性，这反过来又增加了其他来源（如挥发性化学产品）的相对重要性。
We describe simulations using an updated version of the Community Multiscale Air Quality model version 5.3 (CMAQ v5.3) to investigate the contribution of intermediate-volatility organic compounds (IVOCs) to secondary organic aerosol (SOA) formation in southern California during the CalNex study. We first derive a model-ready parameterization for SOA formation from IVOC emissions from mobile sources. To account for SOA formation from both diesel and gasoline sources, the parameterization has six lumped precursor species that resolve both volatility and molecular structure (aromatic versus aliphatic). We also implement new mobile-source emission profiles that quantify all IVOCs based on direct measurements. The profiles have been released in SPECIATE 5.0. By incorporating both comprehensive mobile-source emission profiles for semivolatile organic compounds (SVOCs) and IVOCs and experimentally constrained SOA yields, this CMAQ configuration best represents the contribution of mobile sources to urban and regional ambient organic aerosol (OA). In the Los Angeles region, gasoline sources emit 4 times more non-methane organic gases (NMOGs) than diesel sources, but diesel emits roughly 3 times more IVOCs on an absolute basis. The revised model predicts all mobile sources (including on- and off-road gasoline, aircraft, and on- and off-road diesel) contribute ~ 1 μgm-3 to the daily peak SOA concentration in Pasadena. This represents a ~ 70% increase in predicted daily peak SOA formation compared to the base version of CMAQ. Therefore, IVOCs in mobile-source emissions contribute almost as much SOA as traditional precursors such as single-ring aromatics. However, accounting for these emissions in CMAQ does not reproduce measurements of either ambient SOA or IVOCs. To investigate the potential contribution of other IVOC sources, we performed two exploratory simulations with varying amounts of IVOC emissions from nonmobile sources. To close the mass balance of primary hydrocarbon IVOCs, IVOCs would need to account for 12% of NMOG emissions from nonmobile sources (or equivalently 30.7 t d-1 in the Los Angeles-Pasadena region), a value that is well within the reported range of IVOC content from volatile chemical products. To close the SOA mass balance and also explain the mildly oxygenated IVOCs in Pasadena, an additional 14.8% of nonmobile-source NMOG emissions would need to be IVOCs (assuming SOA yields from the mobile IVOCs apply to nonmobile IVOCs). However, an IVOC-to-NMOG ratio of 26.8% (or equivalently 68.5 t d-1 in the Los Angeles-Pasadena region) for nonmobile sources is likely unrealistically high. Our results highlight the important contribution of IVOCs to SOA production in the Los Angeles region but underscore that other uncertainties must be addressed (multigenerational aging, aqueous chemistry and vapor wall losses) to close the SOA mass balance. This research also highlights the effectiveness of regulations to reduce mobile-source emissions, which have in turn increased the relative importance of other sources, such as volatile chemical products.
影响因子：
6.3
作者：
Fast, J. D.;Allan, J.;Zhang, Q.
通讯作者：
Zhang, Q.