Semi-volatile and highly oxygenated gaseous and particulate organic compounds observed above a boreal forest canopy
Semi-volatile and highly oxygenated gaseous and particulate organic compounds observed above a boreal forest canopy
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DOI：
10.5194/acp-18-11547-2018
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发表时间：
2018-08-15
影响因子：
6.3
通讯作者：
Thornton, Joel A.
中科院分区：
文献类型：
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作者：
Lee, Ben H.;Lopez-Hilfiker, Felipe D.;Thornton, Joel A.
作为生物气溶胶对云和气候的影响(BAECC)活动的一部分，我们从2014年4月到6月每小时在线观测一次气体和亚微米颗粒相中的分子组成(CxHyOzN0-1)和含氧有机物种的丰度。测量是使用气体和气溶胶的过滤器入口进行的，该过滤器与高分辨率飞行时间碘化物加成电离质谱仪(FIGAERO-CIMS)相连，该仪器位于一座35米高的塔顶，位于芬兰海蒂亚拉Smear II研究站北部森林树冠上方约10米处。通常观察到的是半挥发性和高度氧化的多功能(HOM)有机物种，其碳原子从1到20个，氧原子少则2个，多则16个。利用非负矩阵分解，我们确定了气相和颗粒相中的>；90和>；99%的有机质量分别表现出三种不同的趋势之一：一种是在白天，另一种是在清晨，第三种是在夜间。在BAECC期间，颗粒有机硝酸盐对夜间有机气溶胶总质量负荷的贡献类似于35%，远高于同一仪器在美国东南部经历了夜间氮氧化物浓度较高的落叶混交林地点的观测结果。在这两个相的三个亚基中的大多数中都发现了独特的HOM单体(这里定义为具有10个碳原子和7个或更多氧原子的单体)和二聚体(至少16个碳原子)，无论是否含有氮原子。我们展示了基于它们在时间上的不同行为将这些化合物分组与预期的化学条件(生物VOC前体、氧化剂类型等)相联系的潜力。负责他们的生产。在气相和颗粒相中都检测到了一系列硝化的二聚物类化合物，这表明NO3自由基驱动的低挥发性有机物的形成以及白天不受影响的单萜化学可能起到了作用。
We present hourly online observations of molecular compositions (CxHyOzN0-1) and abundances of oxygenated organic species in gas and submicron particle phases from April to June of 2014 as part of the Biogenic Aerosols-Effects on Cloud and Climate (BAECC) campaign. Measurements were made using the Filter Inlet for Gases and AEROsols coupled to a high-resolution time-of-flight iodide-adduct ionization mass spectrometer (FIGAERO-CIMS) located atop a 35m tall tower, about 10m above a boreal forest canopy at the SMEAR II research station in Hyytiala, Finland. Semi-volatile and highly oxygenated multifunctional (HOM) organic species possessing from 1 up to 20 carbon atoms, and with as few as 2 and as many as 16 oxygen atoms, were routinely observed. Utilizing non-negative matrix factorization, we determined that > 90 and > 99% of the organic mass in the gas and particle phases, respectively, exhibited one of three distinct diel trends: one in which abundances were enhanced at daytime, another in the early morning hours, and thirdly during nighttime. Particulate organic nitrates contributed similar to 35% to the total organic aerosol mass loading at night during BAECC, much higher than observed by the same instrument package at a mixed-deciduous forest site in the southeastern US that experienced higher nighttime concentrations of nitrogen oxides. Unique HOM monomers (defined here as those with 10 carbon and 7 or more oxygen atoms) and dimers (at least 16 carbon atoms), with and without a nitrogen atom, were found in most of the three subgroups of both phases. We show the potential to connect these groupings of compounds based on their distinct behavior in time to the expected chemical conditions (biogenic VOC precursor, oxidant type, etc.) responsible for their production. A suite of nitrated dimer-like compounds was detected in both the gas and particle phases, suggesting a potential role for the formation of low-volatility organics from NO3-radical-driven, as well as daytime NO-influenced, monoterpene chemistry.