Understanding the drivers for high ozone (O3) and atmospheric particulate matter (PM) concentrations is a pressing issue in urban air quality, as this understanding informs decisions for control and mitigation of these key pollutants. The Houston, TX metropolitan area is an ideal location for studying the intersection between O3 and atmospheric secondary organic carbon (SOC) production due to the diversity of source types (urban, industrial, and biogenic) and the on- and off-shore cycling of air masses over Galveston Bay, TX. Detailed characterization of filter-based samples collected during Deriving Information on Surface Conditions from Column and VERtically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) Houston field experiment in September 2013 were used to investigate sources and composition of organic carbon (OC) and potential relationships between daily maximum 8 h average O3 and PM. The current study employed a novel combination of chemical mass balance modeling defining primary (i.e. POC) versus secondary (i.e. SOC) organic carbon and radiocarbon (14C) for apportionment of contemporary and fossil carbon. The apportioned sources include contemporary POC (biomass burning [BB], vegetative detritus), fossil POC (motor vehicle exhaust), biogenic SOC and fossil SOC. The filter-based results were then compared with real-time measurements by aerosol mass spectrometry. With these methods, a consistent urban background of contemporary carbon and motor vehicle exhaust was observed in the Houston metropolitan area. Real-time and filter-based characterization both showed that carbonaceous aerosols in Houston was highly impacted by SOC or oxidized OC, with much higher contributions from biogenic than fossil sources. However, fossil SOC concentration and fractional contribution had a stronger correlation with daily maximum 8 h average O3, peaking during high PM and O3 events. The results indicate that point source emissions processed by on- and off-shore wind cycles likely contribute to peak events for both PM and O3 in the greater Houston metropolitan area.

中文翻译：

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DISCOVER-AQ 休斯顿污染事件期间分配的一次和二次有机气溶胶

了解臭氧 (O3) 和大气颗粒物 (PM) 浓度高的驱动因素是城市空气质量的一个紧迫问题，因为这种了解可以为控制和缓解这些关键污染物的决策提供信息。由于来源类型（城市、工业和生物）的多样性以及氧气的陆上和离岸循环，德克萨斯州休斯顿大都市区是研究 O3 与大气二次有机碳 (SOC) 生产之间交叉的理想地点。德克萨斯州加尔维斯顿湾上空的气团。2013 年 9 月休斯敦现场实验中从柱中获取表面条件信息和与空气质量相关的垂直解析观测 (DISCOVER-AQ) 期间收集的基于过滤器的样品的详细表征，用于研究有机碳 (OC) 的来源和组成以及潜力每日最大 8 小时平均 O3 与 PM 之间的关系。当前的研究采用了化学质量平衡模型的新颖组合，定义了初级（即POC）与次级（即SOC）有机碳和放射性碳（14C）来分配当代碳和化石碳。分配的来源包括当代 POC（生物质燃烧 [BB]，植物碎屑）、化石 POC（机动车尾气）、生物 SOC 和化石 SOC。然后将基于过滤器的结果与气溶胶质谱法的实时测量结果进行比较。通过这些方法，在休斯顿都市区观察到了当代碳和机动车尾气的一致城市背景。实时和基于过滤器的表征均表明，休斯顿的碳质气溶胶受到 SOC 或氧化 OC 的严重影响，其中生物来源的贡献远高于化石来源。然而，化石 SOC 浓度和分数贡献与每日最大 8 小时平均 O3 具有更强的相关性，在高 PM 和 O3 事件期间达到峰值。结果表明，陆上和离岸风循环处理的点源排放可能导致休斯顿大都市区 PM 和 O3 的峰值事件。