Despite the central role of reactive organic carbon (ROC) in the formation of secondary species that impact global air quality and climate, our assessment of ROC abundance and impacts is challenged by the diversity of species that contribute to it. We revisit measurements of ROC species made during two field campaigns in the United States: the 2013 SOAS campaign in forested Centreville, AL, and the 2010 CalNex campaign in urban Pasadena, CA. We find that average measured ROC concentrations are about twice as high in Pasadena (73.8 μgCsm^–3) than in Centreville (36.5 μgCsm^–3). However, the OH reactivity (OHR) measured at these sites is similar (20.1 and 19.3 s^–1). The shortfall in OHR when summing up measured contributions is 31%, at Pasadena and 14% at Centreville, suggesting that there may be a larger reservoir of unmeasured ROC at the former site. Estimated O₃ production and SOA potential (defined as concentration × yield) are both higher during CalNex than SOAS. This analysis suggests that the ROC in urban California is less reactive, but due to higher concentrations of oxides of nitrogen and hydroxyl radicals, is more efficient in terms of O₃ and SOA production, than in the forested southeastern U.S.

中文翻译：

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美国东南部（SOAS）和南加州（CalNex）的反应性有机碳对比观测

尽管活性有机碳（ROC）在影响全球空气质量和气候的次生物种形成过程中发挥着核心作用，但我们对ROC丰度和影响的评估仍受到其贡献物种多样性的挑战。我们重新评估了在美国进行的两次野外活动期间进行的ROC物种的测量：2013年在阿拉斯加森林中心森特维尔举行的SOAS活动和2010年在加利福尼亚州帕萨迪纳举行的CalNex活动。我们发现，平均测量ROC浓度约两倍于帕萨迪纳（73.8μgCsm高^-3），比森特维尔（36.5μgCsm ^-3）。但是，在这些位置测得的OH反应性（OHR）相似（20.1和19.3 s ^–1）。帕萨迪纳（Pasadena）的OHR不足，而帕萨迪纳（Centreville）的短缺为31％，这表明以前的地点可能存在更大的未计量ROC储量。在CalNex期间，估计的O ₃产量和SOA潜力（定义为浓度×产量）均高于SOAS。该分析表明，加利福尼亚州市区的ROC反应性较低，但由于氮和羟基自由基的氧化物浓度较高，因此在O ₃和SOA生产方面比在美国东南部森林中更为有效。