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首页> 外文期刊>Atmospheric chemistry and physics >Seasonal cycles of biogenic volatile organic compound fluxes and concentrations in a California citrus orchard
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Seasonal cycles of biogenic volatile organic compound fluxes and concentrations in a California citrus orchard

机译：加州柑桔园中生物挥发性有机化合物通量和浓度的季节性循环

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Orange trees are widely cultivated in Mediterranean climatic regions wherethey are an important agricultural crop. Citrus have been characterized asemitters of volatile organic compounds (VOC) in chamber studies undercontrolled environmental conditions, but an extensive characterization atfield scale has never been performed using modern measurement methods, and isparticularly needed considering the complex interactions between the orchardsand the polluted atmosphere in which Citrus is often cultivated. For oneyear, in a Valencia orange orchard in Exeter, California, we measured fluxesusing PTRMS (Proton Transfer Reaction Mass Spectrometer) and eddy covariancefor the most abundant VOC typically emitted from citrus vegetation: methanol,acetone, and isoprenoids. Concentration gradients of additional oxygenatedand aromatic compounds from the ground level to above the canopy were alsomeasured. In order to characterize concentrations of speciated biogenic VOC(BVOC) in leaves, we analyzed leaf content by GC-MS (Gas Chromatography –Mass Spectrometery) regularly throughout the year. We also characterized inmore detail concentrations of speciated BVOC in the air above the orchard byin-situ GC-MS during a few weeks in spring flowering and summer periods. Herewe report concentrations and fluxes of the main VOC species emitted by theorchard, discuss how fluxes measured in the field relate to previous studiesmade with plant enclosures, and describe how VOC content in leaves andemissions change during the year in response to phenological andenvironmental parameters. The orchard was a source of monoterpenes andoxygenated VOC. The highest emissions were observed during the springtimeflowering period, with mid-day fluxes above 2 nmol m?2 s?1 formethanol and up to 1 nmol m?2 s?1 for acetone and monoterpenes.During hot summer days emissions were not as high as we expected consideringthe known dependence of biogenic emissions on temperature. We provideevidence that thickening of leaf cuticle wax content limited gaseousemissions during the summer.
机译：在地中海气候地区，橙树是重要的农作物，广泛种植。在受控环境条件下的室内研究中，柑橘已被表征为挥发性有机化合物（VOC）的发射者，但从未使用现代测量方法对田间规模进行广泛的表征，特别是考虑到果园与柑橘所污染的大气之间的复杂相互作用，尤其需要经常被耕种。在加利福尼亚州埃克塞特的巴伦西亚橙园，我们用PTRMS（质子转移反应质谱仪）和涡流协方差测量了通常从柑橘类植物排放的最丰富的VOC：甲醇，丙酮和类异戊二烯的通量，为期一年。还测量了从地面到树冠上方的其他含氧和芳香族化合物的浓度梯度。为了表征叶片中特定生物源性VOC（BVOC）的浓度，我们全年定期通过GC-MS（气相色谱-质谱仪）分析叶片含量。我们还通过春季开花和夏季数周的原位GC-MS对果园上方空气中特定BVOC的浓度进行了更详细的表征。在此我们报告了果园排放的主要VOC种类的浓度和通量，讨论了田间测得的通量如何与以前用植物围栏进行的研究相关，并描述了一年中叶片中的VOC含量和排放如何根据物候和环境参数而变化。果园是单萜和氧化VOC的来源。在春季开花期观察到最高的排放，中午通量高于2 nmol m ？2 s ？1 甲醛，最高至1 nmol m ？2 s ？1 用于丙酮和单萜。在炎热的夏季，考虑到已知的生物源排放物对温度的依赖性，其排放量不如我们预期的高。我们提供的证据表明，在夏季，叶片表皮蜡含量的增稠限制了气体排放。

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