Quantifying the Light-Absorption Properties and Molecular Composition of Brown Carbon Aerosol from Sub-Saharan African Biomass Combustion
Quantifying the Light-Absorption Properties and Molecular Composition of Brown Carbon Aerosol from Sub-Saharan African Biomass Combustion
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DOI：
10.1021/acs.est.3c09378
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发表时间：
2024-02-23
影响因子：
11.4
通讯作者：
Surratt，Jason D.
中科院分区：
文献类型：
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作者：
Moschos，Vaios;Christensen，Cade;Surratt，Jason D.
撒哈拉以南非洲是生物质燃烧(BB)产生的碳质气溶胶的热点地区，包括吸收光的有机(棕色)碳(BRC)。然而，该地区BB气溶胶中BRC的化学复杂性还没有完全被了解。我们通过焚烧撒哈拉以南非洲常见的生物质燃料(阔叶木、牛粪、稀树草原和树叶)在一个房间里产生烟雾。考虑到波长、燃料类型、相对湿度和光化学老化条件的变化，我们量化了含溴化氢的富含有机BB气雾剂的气速计实时光吸收特性。在冬季从室内和博茨瓦纳采集的过滤样品中，我们鉴定了182种BRC，分类为木质素热解产物、硝基芳烃、香豆素、二苯乙烯类和类黄酮类。使用一套广泛的标准，我们确定了特定物种的质量和排放系数。我们的分析表明，BRC物种对室内测量的BB气溶胶质量的贡献(0.4-14%)与370 nm处的质量吸收截面(0.2-2.2m2g-1)之间存在线性关系。等级聚类解析了BRC基质中的关键分子水平成分，树叶和牛粪燃烧产生的光化学老化排放显示出与博茨瓦纳气溶胶相似的BRC指纹。这些量化发现可能有助于完善气候模型预测，有助于来源解析，并为有效的空气质量管理政策提供信息，以保障人类健康和全球气候。
Sub-Saharan Africa is a hotspot for biomass burning (BB)-derived carbonaceous aerosols, including light-absorbing organic (brown) carbon (BrC). However, the chemically complex nature of BrC in BB aerosols from this region is not fully understood. We generated smoke in a chamber through smoldering combustion of common sub-Saharan African biomass fuels (hardwoods, cow dung, savanna grass, and leaves). We quantified aethalometer-based, real-time light-absorption properties of BrC-containing organic-rich BB aerosols, accounting for variations in wavelength, fuel type, relative humidity, and photochemical aging conditions. In filter samples collected from the chamber and Botswana in the winter, we identified 182 BrC species, classified into lignin pyrolysis products, nitroaromatics, coumarins, stilbenes, and flavonoids. Using an extensive set of standards, we determined species-specific mass and emission factors. Our analysis revealed a linear relationship between the combined BrC species contribution to chamber-measured BB aerosol mass (0.4–14%) and the mass-absorption cross-section at 370 nm (0.2–2.2 m2g–1). Hierarchical clustering resolved key molecular-level components from the BrC matrix, with photochemically aged emissions from leaf and cow-dung burning showing BrC fingerprints similar to those found in Botswana aerosols. These quantitative findings could potentially help refine climate model predictions, aid in source apportionment, and inform effective air quality management policies for human health and the global climate.