Global atmospheric budget of acetaldehyde: 3-D model analysis and constraints from in-situ and satellite observations
Global atmospheric budget of acetaldehyde: 3-D model analysis and constraints from in-situ and satellite observations
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DOI：
10.5194/acp-10-3405-2010
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发表时间：
2009-11
影响因子：
6.3
通讯作者：
D. Millet;A. Guenther;D. Siegel;N. Nelson;H. Singh;J. Gouw;C. Warneke;Jonathan Williams;G. Eerdekens;V. Sinha;T. Karl;F. Flocke;E. Apel;D. Riemer;P. Palmer;M. Barkley
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文献类型：
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作者：
D. Millet;A. Guenther;D. Siegel;N. Nelson;H. Singh;J. Gouw;C. Warneke;Jonathan Williams;G. Eerdekens;V. Sinha;T. Karl;F. Flocke;E. Apel;D. Riemer;P. Palmer;M. Barkley
抽象。我们构建了一个全球大气预算乙醛使用3-D模型的大气化学（GEOS-Chem），并使用一个合奏的观测，以评估目前的理解，其源和汇。烃氧化提供了模型中最大的乙醛来源（128 Tg a−1，比以前的估计大4倍），烷烃，烯烃和乙醇是主要的前体。还有一个来自异戊二烯氧化的次要来源。我们使用更新的化学机制的GEOS-Chem，和光化学乙醛产率是一致的主化学机制。我们提出了一种新的方法来量化乙醛海气通量的基础上的全球分布的光吸收，由于彩色溶解有机物（CDOM）来自卫星海洋颜色观测。由此产生的海洋净排放量为57 Tg a-1，是全球第二大乙醛来源。一个关键的不确定性是海洋混合层中的乙醛周转时间，在海洋上的定量模型评估由于清洁空气中已知的测量伪影而变得复杂。海洋表面空气中的模拟浓度通常与飞机测量结果吻合良好，尽管该模型往往高估了垂直梯度。PAN：NOx的比例很好地模拟在海洋边界层，模拟海洋源提供了一些支持。我们介绍了乙醛和乙醇的天然气和气溶胶排放模型（MEGANv2.1），并用它来量化它们从陆生植物的净通量。包括腐烂植物的排放，陆地生物圈的乙醛直接来源总量为23 Tg a−1。其他陆地乙醛来源包括生物质燃烧（3 Tg a−1）和人为排放（2 Tg a−1）。大陆边界层的模拟浓度一般是无偏的，并捕捉到北美、欧洲和热带南美洲观测中的空间梯度。然而，该模型低估了城市流出物中的乙醛水平，这表明污染空气中缺少乙醛源。无处不在的高测量浓度在自由对流层中没有捕获的模型，并根据目前的理解是不一致的PAN和NOx的并发测量：我们没有发现令人信服的证据广泛失踪的乙醛源在自由对流层。我们估计，目前美国乙醇和乙醛的来源（初级+二级）为1.3 Tg a−1和7.8 Tg a−1，约为国家从汽油过渡到乙醇燃料的相应增长的60%和480%。
Abstract. We construct a global atmospheric budget for acetaldehyde using a 3-D model of atmospheric chemistry (GEOS-Chem), and use an ensemble of observations to evaluate present understanding of its sources and sinks. Hydrocarbon oxidation provides the largest acetaldehyde source in the model (128 Tg a−1, a factor of 4 greater than the previous estimate), with alkanes, alkenes, and ethanol the main precursors. There is also a minor source from isoprene oxidation. We use an updated chemical mechanism for GEOS-Chem, and photochemical acetaldehyde yields are consistent with the Master Chemical Mechanism. We present a new approach to quantifying the acetaldehyde air-sea flux based on the global distribution of light absorption due to colored dissolved organic matter (CDOM) derived from satellite ocean color observations. The resulting net ocean emission is 57 Tg a−1, the second largest global source of acetaldehyde. A key uncertainty is the acetaldehyde turnover time in the ocean mixed layer, with quantitative model evaluation over the ocean complicated by known measurement artifacts in clean air. Simulated concentrations in surface air over the ocean generally agree well with aircraft measurements, though the model tends to overestimate the vertical gradient. PAN:NOx ratios are well-simulated in the marine boundary layer, providing some support for the modeled ocean source. We introduce the Model of Emissions of Gases and Aerosols from Nature (MEGANv2.1) for acetaldehyde and ethanol and use it to quantify their net flux from living terrestrial plants. Including emissions from decaying plants the total direct acetaldehyde source from the land biosphere is 23 Tg a−1. Other terrestrial acetaldehyde sources include biomass burning (3 Tg a−1) and anthropogenic emissions (2 Tg a−1). Simulated concentrations in the continental boundary layer are generally unbiased and capture the spatial gradients seen in observations over North America, Europe, and tropical South America. However, the model underestimates acetaldehyde levels in urban outflow, suggesting a missing source in polluted air. Ubiquitous high measured concentrations in the free troposphere are not captured by the model, and based on present understanding are not consistent with concurrent measurements of PAN and NOx: we find no compelling evidence for a widespread missing acetaldehyde source in the free troposphere. We estimate the current US source of ethanol and acetaldehyde (primary + secondary) at 1.3 Tg a−1 and 7.8 Tg a−1, approximately 60{%} and 480% of the corresponding increases expected for a national transition from gasoline to ethanol fuel.