Identification of humic-like substances (HULIS) in oxygenated organic aerosols using NMR and AMS factor analyses and liquid chromatographic techniques
Identification of humic-like substances (HULIS) in oxygenated organic aerosols using NMR and AMS factor analyses and liquid chromatographic techniques
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DOI：
10.5194/acp-14-25-2014
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发表时间：
2013
影响因子：
6.3
通讯作者：
M. Paglione;A. Kiendler‐Scharr;A. Mensah;E. Finessi;L. Giulianelli;S. Sandrini;M. Facchini;S. Fuzzi;P. Schlag;A. Piazzalunga;E. Tagliavini;J. Henzing;S. Decesari
中科院分区：
文献类型：
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作者：
M. Paglione;A. Kiendler‐Scharr;A. Mensah;E. Finessi;L. Giulianelli;S. Sandrini;M. Facchini;S. Fuzzi;P. Schlag;A. Piazzalunga;E. Tagliavini;J. Henzing;S. Decesari
大气有机气溶胶组成的特点是官能团和化学物种的多样性，对简单的分类方案提出了挑战。传统的离线化学方法根据色谱柱和吸收床上的保留行为来识别化学类别。这种方法导致了类似腐植酸物质(HULIS)等化合物的复杂混合物的分离。最近，在线气溶胶质谱仪(AMS)被用来识别化学类别，方法是使用统计方法(因子分析)从实验数据序列中提取碎片模式，根据含氧官能团的分布为含氧有机气溶胶(OOAs)提供简化的分类方案。对大量AMS数据集的分析表明，发生了氧化程度很高的OOAs，推测与HULIS相对应。然而，对面向对象的AMS分类与传统的离线分类方法的一致性检验却很少。在这篇文章中，我们考虑了一个受污染的大陆区域背景环境的案例研究代表。我们检查了通过正矩阵分解(PMF)确定的OOAs的AMS因子，并与在一组并行收集的过滤器上离线分析的水溶性有机碳(WSOC)的化学类别进行了比较。通过对核磁共振氢谱数据进行因子分析，并应用离子交换层析法直接定量HULIS，进行了WSOC分级。结果表明，AMS中氧化程度很高的低挥发性OOAs与显示HULIS特征的核磁共振因子相关，也与真正的“色层”HULIS相关。另一方面，在离子交换床上分离的紫外/可见光吸收多酸(或HULIS Sensu Structo)仅占AMS和核磁共振有机碳组分的一小部分，其官能团可归因于高度取代的羧酸，这表明非晶态低分子量有机酸在广义上对HULIS有贡献。
The atmospheric organic aerosol composition is characterized by a great diversity of functional groups and chemical species challenging simple classification schemes. Traditional off-line chemical methods identified chemical classes based on the retention behavior on chromatographic columns and absorbing beds. Such approach led to the isolation of complex mixtures of compounds such as the humic-like substances (HULIS). More recently, on-line aerosol mass spectrometry (AMS) was employed to identify chemical classes by extracting fragmentation patterns from experimental data series using statistical methods (factor analysis), providing simplified schemes for oxygenated organic aerosols (OOAs) classification on the basis of the distribution of oxygen-containing functionalities. The analysis of numerous AMS datasets suggested the occurrence of very oxidized OOAs which were postulated to correspond to the HULIS. However, only a few efforts were made to test the correspondence of the AMS classes of OOAs with the traditional classification from the off-line methods. In this paper, we consider a case study representative for polluted continental regional background environments. We examine the AMS factors for OOAs identified by positive matrix factorization (PMF) and compare to chemical classes of water-soluble organic carbon (WSOC) analysed off-line on a set of filters collected in parallel. WSOC fractionation was performed by means of factor analysis applied to H-NMR spectroscopic data, and by applying an ion-exchange chromatographic method for direct quantification of HULIS. Results show that the very oxidized low-volatility OOAs from AMS correlate with the NMR factor showing HULIS features and also with true “chromatographic” HULIS. On the other hand, UV/VIS-absorbing polyacids (or HULIS sensu stricto) isolated on ion-exchange beds were only a fraction of the AMS and NMR organic carbon fractions showing functional groups attributable to highly substituted carboxylic acids, suggesting that unspeciated low-molecular weight organic acids contribute to HULIS in the broad sense.