Source Apportionment of Brown Carbon Absorption by Coupling Ultraviolet–Visible Spectroscopy with Aerosol Mass Spectrometry,Environmental Science & Technology Letters

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Source Apportionment of Brown Carbon Absorption by Coupling Ultraviolet–Visible Spectroscopy with Aerosol Mass Spectrometry
Environmental Science & Technology Letters ( IF 8.9 ) Pub Date : 2018-05-25 , DOI: 10.1021/acs.estlett.8b00118
Vaios Moschos _{1,

2} , Nivedita K. Kumar ₁ , Kaspar R. Daellenbach ₁ , Urs Baltensperger ₁ , André S. H. Prévôt ₁ , Imad El Haddad ₁

Affiliation

The impact of brown carbon (BrC) on climate has been widely acknowledged but remains uncertain, because either its contribution to absorption is being ignored in most climate models or the associated mixed emission sources and atmospheric lifetime are not accounted for. In this work, we propose positive matrix factorization as a framework to apportion the contributions of individual primary and secondary organic aerosol (OA) source components of BrC absorption, by combining long-term aerosol mass spectrometry (AMS) data with concurrent ultraviolet–visible (UV-vis) spectroscopy measurements. The former feature time-dependent factor contributions to OA mass, and the latter consist of wavelength-dependent absorption coefficients. Using this approach for a full-year case study, we estimate for the first time the mass absorption efficiency (MAE) of major light-absorbing water-soluble OA components in the atmosphere. We show that secondary biogenic OA contributes negligibly to absorption despite dominating the mass concentration in the summer. In contrast, primary and secondary wood burning emissions are highly absorbing up to 500 nm. The approach allowed us to constrain their MAE within a confined range consistent with previous laboratory work, which can be used in climate models to estimate the impact of BrC from these emissions on the overall absorption.

中文翻译：

紫外-可见光谱与气溶胶质谱联用分析棕色碳的吸收源

棕色碳（BrC）对气候的影响已得到广泛认可，但仍不确定，因为在大多数气候模型中，棕色碳对吸收的贡献都被忽略了，或者未考虑相关的混合排放源和大气寿命。在这项工作中，我们建议采用正矩阵分解作为框架，通过将长期气溶胶质谱（AMS）数据与并发的紫外可见光（紫外可见光谱测量。前者具有与时间相关的因素对OA质量的贡献，而后者则具有与波长有关的吸收系数。使用这种方法进行全年的案例研究，我们首次估算了大气中主要吸光水溶性OA组分的质量吸收效率（MAE）。我们显示，尽管占主导地位的夏季，中学生物成因OA吸收的贡献微不足道。相比之下，一次和二次木材燃烧排放物可吸收高达500 nm的光。该方法使我们能够将其MAE限制在与先前实验室工作一致的限定范围内，该范围可用于气候模型中，以估算这些排放物中BrC对总吸收量的影响。一次和二次木材燃烧排放物吸收高达500 nm。该方法使我们能够将其MAE限制在与先前实验室工作一致的限定范围内，该范围可用于气候模型中，以估算这些排放物中BrC对总吸收量的影响。一次和二次木材燃烧排放物吸收高达500 nm。该方法使我们能够将其MAE限制在与先前实验室工作一致的限定范围内，该范围可用于气候模型中，以估算这些排放物中BrC对总吸收量的影响。

更新日期：2018-05-27

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