Evidence for an unidentified non-photochemical ground-level source of formaldehyde in the Po Valley with potential implications for ozone production
Evidence for an unidentified non-photochemical ground-level source of formaldehyde in the Po Valley with potential implications for ozone production
复制标题
DOI：
10.5194/acp-15-1289-2015
复制
发表时间：
2015-02
影响因子：
6.3
通讯作者：
J. Kaiser;G. Wolfe;B. Bohn;S. Broch;H. Fuchs;L. Ganzeveld;S. Gomm;R. Häseler;A. Hofzumahaus;F. Holland;J. Jäger;Xin Li;I. Lohse;K. Lu;A. Prévôt;F. Rohrer;R. Wegener;R. Wolf;T. Mentel;A. Kiendler‐Scharr;A. Wahner;F. Keutsch
中科院分区：
文献类型：
--
作者：
J. Kaiser;G. Wolfe;B. Bohn;S. Broch;H. Fuchs;L. Ganzeveld;S. Gomm;R. Häseler;A. Hofzumahaus;F. Holland;J. Jäger;Xin Li;I. Lohse;K. Lu;A. Prévôt;F. Rohrer;R. Wegener;R. Wolf;T. Mentel;A. Kiendler‐Scharr;A. Wahner;F. Keutsch
抽象。意大利北方波河流域的臭氧浓度经常超过国际规定。作为自由基的来源和大多数挥发性有机化合物（VOC）氧化的中间体，甲醛（HCHO）是导致臭氧产生的烃氧化处理的有用示踪剂。我们调查的来源，甲醛在波河流域使用垂直剖面测量获得的飞艇齐柏林NT在一个农业区在PEGASOS 2012年活动。使用1-D模型，总VOC氧化率进行检查和讨论的背景下，甲醛和臭氧的生产在清晨。虽然OH反应性的模型和测量差异很小（平均3.4 ± 13%），但对流混合层中的甲醛浓度被低估了1.5 ppb（45%）。在2002-2003年FORMAT Po Valley的测量中也发现了类似的甲醛低估，尽管没有确定甲醛的额外来源。未测量的VOC前体的氧化不能解释缺失的HCHO源，因为测量的OH反应性可以通过测量的VOC及其计算的氧化产物来解释。我们的结论是，农业用地的本地直接排放是HCHO缺失的最可能来源。模型计算表明，这种非光化学HCHO源降解产生的自由基在中午之前使模型臭氧产生率增加了0.6 ppb h−1（12%）。
Abstract. Ozone concentrations in the Po Valley of northern Italy often exceed international regulations. As both a source of radicals and an intermediate in the oxidation of most volatile organic compounds (VOCs), formaldehyde (HCHO) is a useful tracer for the oxidative processing of hydrocarbons that leads to ozone production. We investigate the sources of HCHO in the Po Valley using vertical profile measurements acquired from the airship Zeppelin NT over an agricultural region during the PEGASOS 2012 campaign. Using a 1-D model, the total VOC oxidation rate is examined and discussed in the context of formaldehyde and ozone production in the early morning. While model and measurement discrepancies in OH reactivity are small (on average 3.4 ± 13%), HCHO concentrations are underestimated by as much as 1.5 ppb (45%) in the convective mixed layer. A similar underestimate in HCHO was seen in the 2002–2003 FORMAT Po Valley measurements, though the additional source of HCHO was not identified. Oxidation of unmeasured VOC precursors cannot explain the missing HCHO source, as measured OH reactivity is explained by measured VOCs and their calculated oxidation products. We conclude that local direct emissions from agricultural land are the most likely source of missing HCHO. Model calculations demonstrate that radicals from degradation of this non-photochemical HCHO source increase model ozone production rates by as much as 0.6 ppb h−1 (12%) before noon.