Observations and modelling of glyoxal in the tropical Atlantic marine boundary layer
Observations and modelling of glyoxal in the tropical Atlantic marine boundary layer
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DOI：
10.5194/acp-2021-940
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发表时间：
2021-11
影响因子：
6.3
通讯作者：
H. Walker;D. Stone;T. Ingham;S. Hackenberg;D. Cryer;S. Punjabi;K. Read;James D. Lee;L. Whalley
中科院分区：
文献类型：
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作者：
H. Walker;D. Stone;T. Ingham;S. Hackenberg;D. Cryer;S. Punjabi;K. Read;James D. Lee;L. Whalley
抽象的。在2014年6月至7月和8月至9月的两次为期4周的活动期间，在佛得角大气观测站（CVAO，16° 52' N，24° 52' W）对热带海洋边界层表面的乙二醛进行了现场测量，时间分辨率为几分钟。使用激光诱导磷光光谱，仪器检测限为~1 pptv（1小时平均值），观察到体积混合比高达~10 pptv，在第一次和第二次活动期间观察到的24小时平均混合比分别为4.9 pptv和6.3 pptv。观察到一些昼夜行为，但这并不明显。箱模型使用详细的主化学机制（3.2版）和约束的一套物种的详细观察共同测量的天文台被用来计算乙二醛混合比。一般模型低估了两个活动期间的乙二醛观测值，两个活动的平均中午（1100-1300小时）乙二醛的模拟比值分别为3.2和4.2，夜间比值更高。生产率分析表明，乙二醛在这种环境中的主要来源是OH与乙醇醛和乙炔的反应，其中OH与过氧化物HC（O）CH 2 OOH的反应有很大贡献，后者本身来自乙醛的OH氧化。乙醛的混合比增加，这是不受约束的，并可能低估的基础模型，可以显着提高白天观察到的和建模的乙二醛之间的协议。平均中午的模拟乙二醛比下降到1.3和1.8，分别为活动1和2，约束到一个固定的乙醛混合比为200 pptv，这是一致的，最近的空气中的测量CVAO附近。然而，一个显着的模型低估仍然在夜间。该模型是敏感的模型中间体的沉积速率和乙二醛到气溶胶的吸收的变化。中午（1100-1300）的平均模拟乙二醛混合比减少了0.87和0.90倍的模型中间体的沉积速率和乙二醛的气溶胶吸收，分别增加了1.10和1.06倍的模型中间体的沉积速率和乙二醛的气溶胶吸收，分别。虽然测得的单萜在网站上的水平（总约1 pptv）没有显着影响模型计算的乙二醛水平，空气从一个源区域与高单萜排放量的网站有可能给乙二醛的混合比升高单萜氧化产物，但这些值是高度敏感的沉积速率这些氧化的中间体。根据这项工作，不能排除海洋表面有机微层产生乙二醛的来源，而且在夜间可能很重要。
Abstract. In situ field measurements of glyoxal at the surface in the tropical marine boundary layer have been made with a temporal resolution of a few minutes during two 4-week campaigns in June–July and August–September 2014 at the Cape Verde Atmospheric Observatory (CVAO, 16° 52’ N, 24° 52’ W). Using laser-induced phosphorescence spectroscopy with an instrumental detection limit of ~1 pptv (1 hour averaging), volume mixing ratios up to ~10 pptv were observed, with 24 hour averaged mixing ratios of 4.9 pptv and 6.3 pptv observed during the first and second campaigns, respectively. Some diel behaviour was observed but this was not marked. A box model using the detailed Master Chemical Mechanism (version 3.2) and constrained with detailed observations of a suite of species co-measured at the observatory was used to calculate glyoxal mixing ratios. There is a general model underestimation of the glyoxal observations during both campaigns, with mean midday (1100–1300 hours) observed-to-modelled ratios for glyoxal of 3.2 and 4.2 for the two campaigns, respectively, and higher ratios at night. A rate of production analysis shows the dominant sources of glyoxal in this environment to be the reactions of OH with glycoaldehyde and acetylene, with a significant contribution from the reaction of OH with the peroxide HC(O)CH2OOH, which itself derives from OH oxidation of acetaldehyde. Increased mixing ratios of acetaldehyde, which is unconstrained and potentially underestimated in the base model, can significantly improve the agreement between the observed and modelled glyoxal during the day. Mean midday observed-to-modelled glyoxal ratios decreased to 1.3 and 1.8 for campaigns 1 and 2, respectively, on constraint to a fixed acetaldehyde mixing ratio of 200 pptv, which is consistent with recent airborne measurements near CVAO. However, a significant model underprediction remains at night. The model was sensitive to changes in deposition rates of model intermediates and the uptake of glyoxal onto aerosol. The midday (1100–1300) mean modelled glyoxal mixing ratio decreased by factors of 0.87 and 0.90 on doubling the deposition rates of model intermediates and aerosol uptake of glyoxal, respectively, and increased by factors of 1.10 and 1.06 on halving the deposition rates of model intermediates and aerosol uptake of glyoxal, respectively. Although measured levels of monoterpenes at the site (total of ~1 pptv) do not significantly influence the model calculated levels of glyoxal, transport of air from a source region with high monoterpene emissions to the site has the potential to give elevated mixing ratios of glyoxal from monoterpene oxidation products, but the values are highly sensitive to the deposition rates of these oxidised intermediates. A source of glyoxal derived from production in the ocean surface organic microlayer cannot be ruled out on the basis of this work, and may be significant at night.