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首页> 外文期刊>Atmospheric chemistry and physics >Contrasting winter and summer VOC mixing ratios at a forest site in the Western Mediterranean Basin: the effect of local biogenic emissions
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Contrasting winter and summer VOC mixing ratios at a forest site in the Western Mediterranean Basin: the effect of local biogenic emissions

机译：西地中海盆地森林地点冬季和夏季VOC混合比例的对比：当地生物成因排放的影响

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Atmospheric volatile organic compounds (VOCs) are involved in ozone andaerosol generation, thus having implications for air quality and climate.VOCs and their emissions by vegetation also have important ecological rolesas they can protect plants from stresses and act as communication cuesbetween plants and between plants and animals. In spite of these keyenvironmental and biological roles, the reports on seasonal and daily VOCmixing ratios in the literature for Mediterranean natural environments arescarce.We conducted seasonal (winter and summer) measurements of VOC mixing ratiosin an elevated (720 m a.s.l.) holm oak Mediterranean forest site near themetropolitan area of Barcelona (NE Iberian Peninsula). Methanol was the mostabundant compound among all the VOCs measured in both seasons. Whilearomatic VOCs showed almost no seasonal variability, short-chain oxygenatedVOCs presented higher mixing ratios in summer, presumably due to greateremission by vegetation and increased photochemistry, both enhanced by thehigh temperatures and solar radiation in summer. Isoprenoid VOCs showed thebiggest seasonal change in mixing ratios: they increased by one order ofmagnitude in summer, as a result of the vegetation's greater physiologicalactivity and emission rates. The maximum diurnal concentrations of ozoneincreased in summer too, most likely due to more intense photochemicalactivity and the higher levels of VOCs in the air.The daily variation of VOC mixing ratios was mainly governed by the windregime of the mountain, as the majority of the VOC species analyzed followeda very similar diel cycle. Mountain and sea breezes that develop aftersunrise advect polluted air masses to the mountain. These polluted airmasses had previously passed over the urban and industrial areas surroundingthe Barcelona metropolitan area, where they were enriched in NOx and inVOCs of biotic and abiotic origin. Moreover, these polluted air massesreceive additional biogenic VOCs emitted in the local valley by thevegetation, thus enhancing O3 formation in this forested site. The onlyVOC species that showed a somewhat different daily pattern were monoterpenesbecause of their local biogenic emission. Isoprene also followed in part thedaily pattern of monoterpenes, but only in summer when its biotic sourceswere stronger. The increase by one order of magnitude in the concentrationsof these volatile isoprenoids highlights the importance of local biogenicsummer emissions in these Mediterranean forested areas which also receivepolluted air masses from nearby or distant anthropic sources.
机译：大气挥发性有机化合物（VOC）参与臭氧和气溶胶的产生，因此对空气质量和气候有影响.VOC及其由植物排放的污染物也具有重要的生态作用，因为它们可以保护植物免受压力并充当植物之间以及植物与植物之间的交流线索。动物。尽管有这些关键的环境和生物学作用，但有关地中海自然环境的文献中季节性和每日VOC混合比的报道仍然很少。 我们在海拔较高（720 m）的季节（冬季和夏季）进行了VOC混合比的测量。 asl）霍尔姆橡树地中海森林遗址，位于巴塞罗那（新西伯利亚伊比利亚半岛）主题区附近。在两个季节中，甲醇是所有挥发性有机化合物中含量最高的化合物。芳香族挥发性有机化合物几乎没有季节性变化，而短链含氧挥发性有机化合物在夏季呈现出更高的混合比，这大概是由于植被的排放增加和光化学增加所致，夏季高温和太阳辐射都增强了这种作用。类异戊二烯的挥发性有机化合物在混合比上显示出最大的季节性变化：由于植被的更大的生理活性和排放速率，它们在夏季增加了一个数量级。夏季最大臭氧日浓度也增加，这很可能是由于更强烈的光化学活性和空气中VOC的含量较高。 VOC混合比的每日变化主要受山区风况的影响，因为分析的大多数VOC种类都遵循非常相似的diel循环。日出后形成的山海风将被污染的空气团吹向山上。这些受污染的气团先前已经过巴塞罗那大都市区周围的城市和工业区，在那里富含生物和非生物来源的NO x 和inVOC。此外，这些受污染的气团还接受了植被在当地山谷中排放的其他生物VOC，从而增强了该林地中O 3 的形成。唯一显示每日模式有所不同的VOC物种是单萜，因为它们具有局部生物成因。异戊二烯也部分遵循单萜的日常模式，但仅在其生物来源更强的夏季才出现。这些挥发性类异戊二烯的浓度增加一个数量级，凸显了这些地中海林区当地生源性夏季排放物的重要性，这些地区还从附近或远距离的人类源头接收到了受污染的空气团。

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