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Composition of Size-Resolved Aged Boreal Fire Aerosols: Brown Carbon, Biomass Burning Tracers, and Reduced Nitrogen
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2018-02-06 00:00:00 , DOI: 10.1021/acsearthspacechem.7b00137
Robert A. Di Lorenzo 1 , Bryan K. Place 1 , Trevor C. VandenBoer 2 , Cora J. Young 1
Affiliation  

Aerosols that were size-resolved into 13 fractions between 10 nm and 18 μm were collected from an aged boreal forest wildfire plume in July 2013. Samples were extracted into water and analyzed for molecular-size-resolved brown carbon (BrC), biomass burning (BB) markers, reduced nitrogen compounds, and elemental composition. Absorption of BrC was primarily in fine-mode aerosols and dominated by high-molecular-weight compounds (>500 Da). The molecular size distribution of BrC was conserved across aerosol sizes, with a decrease in the importance of large molecules in smaller aerosols. The aerosol-size-resolved composition of BrC absorption was different than those of the two BB markers, non-sea-salt potassium and levoglucosan, suggesting that they may not be suitable for identifying BB BrC in aged plumes. Strong correlations were observed between BrC and the reduced nitrogen compounds ammonium, dimethylamine, and diethylamine. In aerosols with high BrC and reduced nitrogen, there was a strong cationic excess. These observations could be caused by (i) uptake of ammonium and alkylamines to form stable salts with organic acids or (ii) reactive uptake to form imines or enamines that were hydrolyzed during the BrC extraction process.

中文翻译:

尺寸分辨的老化的北方火气溶胶的组成:棕碳,生物质燃烧示踪剂和减少的氮

2013年7月,从一个古老的北方森林野火羽流中收集了尺寸分解为13个介于10 nm和18μm之间的气溶胶。将样品提取到水中,并分析了分子尺寸分解的褐碳(BrC),生物质燃烧( BB)标记,还原的氮化合物和元素组成。BrC的吸收主要在精细模式的气溶胶中,并且以高分子量化合物(> 500 Da)为主。BrC的分子大小分布在不同的气溶胶尺寸中均保持不变,大分子在较小的气溶胶中的重要性降低。BrC吸收的气溶胶大小分辨成分与非海盐钾和左旋葡聚糖这两个BB标记的成分不同,这表明它们可能不适合鉴定老羽中的BB BrC。在BrC和还原的氮化合物铵,二甲胺和二乙胺之间观察到强相关性。在具有高BrC和减少的氮的气溶胶中,存在强烈的阳离子过量。这些观察结果可能是由于(i)吸收铵和烷基胺以与有机酸形成稳定的盐,或(ii)反应性吸收以形成在BrC萃取过程中水解的亚胺或烯胺。
更新日期:2018-02-06
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