Airborne observations of IEPOX-derived isoprene SOA in the Amazon during SAMBBA
Airborne observations of IEPOX-derived isoprene SOA in the Amazon during SAMBBA
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DOI：
10.5194/acp-14-11393-2014
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发表时间：
2014-01-01
影响因子：
6.3
通讯作者：
Coe, H.
中科院分区：
文献类型：
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作者：
Allan, J. D.;Morgan, W. T.;Coe, H.
异戊二烯是一个潜在的高度重要的，但目前缺乏量化的二次有机气溶胶（SOA）来源。这在热带地区尤其重要，那里的大片雨林是异戊二烯的重要来源。甲基呋喃在分析过程中通过热分解产生，最近被认为是通过异戊二烯环氧二醇（IEPOX）途径形成异戊二烯SOA的标记物，该途径主要发生在低NOx条件下。这在Aerodyne气溶胶质谱仪（AMS）数据中表现为m/z = 82处的峰值。在这里，我们介绍了在南美生物质燃烧分析（SAMBBA）活动期间，英国机载大气测量设施（FAAM） BAe-146研究飞机在亚马逊雨林上空进行的五次飞行中测量的这一标记物的研究。该标记存在和不存在的情况与酸性种子颗粒、较低的氮氧化物浓度和较高的湿度的存在进行对比和联系。也有数据表明有机氮在颗粒物组成中起作用。此外，对该标志的垂直趋势的检查表明，浓度在边界层顶部最高（可能是由于半挥发性再分配），而向上通过自由对流层，质谱剖面向低挥发性氧化气溶胶演变。这些观察结果提供了对亚马逊雨林上方iepox衍生的SOA形成行为的见解，以及甲基呋喃作为该过程标记物的适用性。
Isoprene is a potentially highly significant but currently poorly quantified source of secondary organic aerosols (SOA). This is especially important in the tropics, where large rainforests act as significant sources of isoprene. Methylfuran, produced through thermal decomposition during analysis, has recently been suggested as a marker for isoprene SOA formation through the isoprene epoxydiol (IEPOX) route, which mostly occurs under low NOx conditions. This is manifested as a peak at m/z = 82 in Aerodyne Aerosol Mass Spectrometer (AMS) data. Here we present a study of this marker measured during five flights over the Amazon rainforest on board the UK Facility for Airborne Atmospheric Measurement (FAAM) BAe-146 research aircraft during the South American Biomass Burning Analysis (SAMBBA) campaign. Cases where this marker is and is not present are contrasted and linked to the presence of acidic seed particles, lower NOx concentrations and higher humidities. There are also data to suggest a role of organic nitrogen in the particulate composition. Furthermore, an inspection of the vertical trends of the marker indicates that concentrations are highest at the top of the boundary layer (possibly due to semivolatile repartitioning) and that upwards through the free troposphere, the mass spectral profile evolves towards that of low volatility oxygenated aerosol. These observations offer insights into the behaviour of IEPOX-derived SOA formation above the Amazon rainforest and the suitability of methylfuran as a marker for this process.