Abstract. The declining trend in vehicle emissions has underscored the growing significance of volatile organic compound (VOC) emissions from volatile chemical products (VCPs). However, accurately representing VOC chemistry in simplified chemical mechanisms remains challenging due to its chemical complexity including speciation and reactivity. Previous studies have predominantly focused on VOCs from fossil fuel sources, leading to an underrepresentation of VOC chemistry from VCP sources. We developed an integrated chemical mechanism, RACM2B-VCP, that is compatible with WRF-Chem and is aimed at enhancing the representation of VOC chemistry, particularly from VCP sources, within the present urban environment. Evaluation against the Air Quality System (AQS) network data demonstrates that our model configured with RACM2B-VCP reproduces both the magnitude and spatial variability of O3 and PM2.5 in Los Angeles. Furthermore, evaluation against comprehensive measurements of O3 and PM2.5 precursors from the Reevaluating the Chemistry of Air Pollutants in California (RECAP-CA) airborne campaign and the Southwest Urban NOx and VOC Experiment (SUNVEx) ground site and mobile laboratory campaign confirm the model's accuracy in representing NOx and many VOCs and highlight remaining biases. Although there exists an underprediction in the total VOC reactivity of observed VOC species, our model with RACM2B-VCP exhibits good agreement for VOC markers emitted from different sectors, including biogenic, fossil fuel, and VCP sources. Through sensitivity analyses, we probe the contributions of VCP and fossil fuel emissions to total VOC reactivity and O3. Our results reveal that 52 % of the VOC reactivity and 35 % of the local enhancement of MDA8 O3 arise from anthropogenic VOC emissions in Los Angeles. Significantly, over 50 % of this anthropogenic fraction of either VOC reactivity or O3 is attributed to VCP emissions. The RACM2B-VCP mechanism created, described, and evaluated in this work is ideally suited for accurately representing ozone for the right reasons in the present urban environment where mobile, biogenic, and VCP VOCs are all important contributors to ozone formation.

中文翻译：

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WRF-Chem 更好地展示了挥发性有机化合物化学及其对洛杉矶上空臭氧的影响

摘要。车辆排放量的下降趋势凸显了挥发性化学产品 (VCP) 中挥发性有机化合物 (VOC) 排放的重要性。然而，由于其化学复杂性（包括形态和反应性），以简化的化学机制准确表示 VOC 化学仍然具有挑战性。之前的研究主要集中在化石燃料来源的 VOC 上，导致 VCP 来源的 VOC 化学代表性不足。我们开发了一种集成化学机制 RACM2B-VCP，它与 WRF-Chem 兼容，旨在增强 VOC 化学的代表性，特别是来自 VCP 来源的挥发性有机化合物化学在当前城市环境中的代表性。对空气质量系统 (AQS) 网络数据的评估表明，我们配置了 RACM2B-VCP 的模型再现了洛杉矶 O3 和 PM2.5 的强度和空间变化。此外，根据加州空气污染物化学重新评估 (RECAP-CA) 机载活动以及西南城市氮氧化物和挥发性有机化合物实验 (SUNVEx) 地面站点和移动实验室活动对 O3 和 PM2.5 前体的综合测量进行的评估证实了该模型的准确表示氮氧化物和许多挥发性有机化合物，并强调剩余的偏差。尽管对观察到的 VOC 物种的总 VOC 反应性存在低估，但我们使用 RACM2B-VCP 的模型对不同部门（包括生物源、化石燃料和 VCP 来源）排放的 VOC 标记表现出良好的一致性。通过敏感性分析，我们探讨了 VCP 和化石燃料排放对总 VOC 反应性和 O3 的贡献。我们的结果表明，洛杉矶 52% 的 VOC 反应性和 35% 的 MDA8 O3 局部增强来自于人为 VOC 排放。值得注意的是，VOC 反应性或 O3 中超过 50% 的人为部分归因于 VCP 排放。本工作中创建、描述和评估的 RACM2B-VCP 机制非常适合在当前城市环境中准确地表示臭氧，在当前城市环境中，移动、生物和 VCP VOC 都是臭氧形成的重要贡献者。