Characterization of a real-time tracer for isoprene epoxydiols-derived secondary organic aerosol (IEPOX-SOA) from aerosol mass spectrometer measurements
Characterization of a real-time tracer for isoprene epoxydiols-derived secondary organic aerosol (IEPOX-SOA) from aerosol mass spectrometer measurements
复制标题
DOI：
10.5194/acp-15-11807-2015
复制
发表时间：
2015-01-01
影响因子：
6.3
通讯作者：
Jimenez, J. L.
中科院分区：
文献类型：
--
作者：
Hu, W. W.;Campuzano-Jost, P.;Jimenez, J. L.
异戊二烯环氧二醇（IEPOX）主要是异戊二烯在低no条件下的氧化产物，可形成大量的二次有机气溶胶（SOA）。通过将正矩阵分解（PMF）应用于气溶胶质谱仪（AMS）测量，对总IEPOX-SOA（可能包括其他平行异戊二烯氧化途径形成的SOA）进行了量化。本文总结了在多个大陆的多个实地研究中有机气溶胶（OA）的IEPOX- soa组分，并显示出与GEOS-Chem化学输运模型模拟的气相IEPOX浓度一致的模式。在南方氧化剂和气溶胶研究（SOAS）中，78%的pmf解决的IEPOX-SOA是由测量的IEPOX-SOA分子示踪剂（2-甲基四醇、c5 -三醇和iepox衍生的有机硫酸盐及其二聚体）所占的，使其成为我们所知的环境SOA组件的最高水平的分子识别。在pmf分辨的IEPOX-SOA光谱中发现了c5h60 + (m/z 82)的增强信号。为了研究该离子作为IEPOX-SOA示踪剂的适用性，我们跨多个场、室和源数据集检查了fC(5)H(6)O (fC（5)H(6)O = c5h60 + / OA）。在受到城市、生物质燃烧和其他人为原生有机气溶胶（POA）强烈影响的研究中，观测到的背景值类似于1.7 +/- 0.1‰（千分之一=千分之一）。在受到单萜烯排放强烈影响的研究中，发现较高的背景值为3.1 +/- 0.6‰。实验室单萜烯SOA的平均值（5.5 +/- 2.0 ppm）比IEPOX-SOA的平均值（22 +/- 7 ppm）低4倍，这就为区分这两种对OA的贡献留下了一些空间。在低no水平下受异戊二烯排放强烈影响的地点，其fC(5)H(6)O（类似于平均6.5 +/- 2.2 ppm /千分之一）高于其他地点，这与这些研究中预期的IEPOX- SOA形成一致。IEPOX- SOA中的fC(5)H(6)O总是升高（12-40‰），但在不同位置之间差异很大，这反映了其详细分子组成的巨大差异。在非IEPOX衍生的异戊二烯-SOA中报告的低fC(5)H(6)O（<千分之三）表明，该示踪剂离子在IEPOX- SOA中被特异性增强，并不是来自异戊二烯的所有SOA的示踪剂。我们引入了一种图形诊断来研究ipox - SOA的存在和老化，作为f（CO2）与fC(5)H(6)O的三角形图。最后，我们开发了一种简化的方法来估计环境中的ipox - SOA质量浓度，与完整的PMF方法相比，该方法表现良好。如果本地IEPOX- SOA的fC(5)H(6)O不可用，则示踪方法的不确定性高达类似于2的因子。当只有单位质量分辨率的数据可用时，如气溶胶化学形态监测仪（ACSM），由于其他离子在m/z 82的干扰增加，所有方法的性能都可能不太好。本研究阐明了用于检测ipox - SOA的不同AMS方法的优势和局限性，并将改进该OA组件的表征。
Substantial amounts of secondary organic aerosol (SOA) can be formed from isoprene epoxydiols (IEPOX), which are oxidation products of isoprene mainly under low-NO conditions. Total IEPOX-SOA, which may include SOA formed from other parallel isoprene oxidation pathways, was quantified by applying positive matrix factorization (PMF) to aerosol mass spectrometer (AMS) measurements. The IEPOX-SOA fractions of organic aerosol (OA) in multiple field studies across several continents are summarized here and show consistent patterns with the concentration of gas-phase IEPOX simulated by the GEOS-Chem chemical transport model. During the Southern Oxidant and Aerosol Study (SOAS), 78% of PMF-resolved IEPOX-SOA is accounted by the measured IEPOX-SOA molecular tracers (2-methyltetrols, C5-Triols, and IEPOX-derived organosulfate and its dimers), making it the highest level of molecular identification of an ambient SOA component to our knowledge. An enhanced signal at C5H6O+ (m/z 82) is found in PMF-resolved IEPOX-SOA spectra. To investigate the suitability of this ion as a tracer for IEPOX-SOA, we examine fC(5)H(6)O (fC(5)H(6)O = C5H6O+ / OA) across multiple field, chamber, and source data sets. A background of similar to 1.7 +/- 0.1 parts per thousand (parts per thousand = parts per thousand) is observed in studies strongly influenced by urban, biomass-burning, and other anthropogenic primary organic aerosol (POA). Higher background values of 3.1 +/- 0.6 parts per thousand are found in studies strongly influenced by monoterpene emissions. The average laboratory monoterpene SOA value (5.5 +/- 2.0 parts per thousand) is 4 times lower than the average for IEPOX-SOA (22 +/- 7 parts per thousand), which leaves some room to separate both contributions to OA. Locations strongly influenced by isoprene emissions under low-NO levels had higher fC(5)H(6)O (similar to 6.5 +/- 2.2 parts per thousand on average) than other sites, consistent with the expected IEPOX- SOA formation in those studies. fC(5)H(6)O in IEPOX- SOA is always elevated (12-40 parts per thousand) but varies substantially between locations, which is shown to reflect large variations in its detailed molecular composition. The low fC(5)H(6)O (< 3 parts per thousand) reported in non-IEPOX-derived isoprene-SOA from chamber studies indicates that this tracer ion is specifically enhanced from IEPOX- SOA, and is not a tracer for all SOA from isoprene. We introduce a graphical diagnostic to study the presence and aging of IEPOX- SOA as a triangle plot of f(CO2) vs. fC(5)H(6)O. Finally, we develop a simplified method to estimate ambient IEPOX- SOA mass concentrations, which is shown to perform well compared to the full PMF method. The uncertainty of the tracer method is up to a factor of similar to 2, if the fC(5)H(6)O of the local IEPOX- SOA is not available. When only unit mass-resolution data are available, as with the aerosol chemical speciation monitor (ACSM), all methods may perform less well because of increased interferences from other ions at m/z 82. This study clarifies the strengths and limitations of the different AMS methods for detection of IEPOX- SOA and will enable improved characterization of this OA component.