Brown carbon and internal mixing in biomass burning particles
Brown carbon and internal mixing in biomass burning particles
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DOI：
10.1073/pnas.1206575109
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发表时间：
2012-09-11
影响因子：
11.1
通讯作者：
Schwarz, Joshua P.
中科院分区：
文献类型：
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作者：
Lack, Daniel A.;Langridge, Justin M.;Schwarz, Joshua P.
生物质燃烧（BB）向大气中排放了大量的黑碳（BC）和颗粒物有机物质（POM），对地球的辐射平衡做出了重大贡献。BB粒子可以是一个复杂的光学系统，其散射和吸收来自BC， BC和POM的内部混合物，以及POM的波长依赖性吸收。大量聚甲醛也可以外部混合。我们报告了干燥和热剥蚀吸收的多波长光声测量的独特能力，以解构这种复杂的波长依赖的吸收和混合系统。对来自科罗拉多州博尔德附近四英里峡谷大火的BB粒子的光学测量表明，BC和POM的内部混合物提高了高达70%的吸收率。这些数据支持POM在532 nm处吸收非常弱的假设。404 nm处的增强吸收超过BC吸收的200%，并且随着POM质量的变化而变化，表明POM被吸收。BC和POM的内部混合吸收占404 nm总吸收的19(+/- 8)%，而BC单独吸收占54(+/- 16)%。大约83%的POM质量是外部混合的，其吸收占总粒子吸收的27(+/- 15)%（在404 nm处）。POM在404 nm处的赝折射率和质量吸收效率（MAE）在整个采样周期内发生变化，分别为0.007 +/- 0.005和0.82 +/- 0.43 m(2) g（-1）。我们的分析表明，如果不包括POM和BC的内部混合吸收，POM的MAE可以高达50%的偏置。
Biomass burning (BB) contributes large amounts of black carbon (BC) and particulate organic matter (POM) to the atmosphere and contributes significantly to the earth's radiation balance. BB particles can be a complicated optical system, with scattering and absorption contributions from BC, internal mixtures of BC and POM, and wavelength-dependent absorption of POM. Large amounts of POM can also be externally mixed. We report on the unique ability of multi-wavelength photo-acoustic measurements of dry and thermal-denuded absorption to deconstruct this complicated wavelength-dependent system of absorption and mixing. Optical measurements of BB particles from the Four Mile Canyon fire near Boulder, Colorado, showed that internal mixtures of BC and POM enhanced absorption by up to 70%. The data supports the assumption that the POM was very weakly absorbing at 532 nm. Enhanced absorption at 404 nm was in excess of 200% above BC absorption and varied as POM mass changed, indicative of absorbing POM. Absorption by internal mixing of BC and POM contributed 19(+/- 8)% to total 404-nm absorption, while BC alone contributed 54(+/- 16)%. Approximately 83% of POM mass was externally mixed, the absorption of which contributed 27(+/- 15)% to total particle absorption (at 404 nm). The imaginary refractive index and mass absorption efficiency (MAE) of POM at 404 nm changed throughout the sampling period and were found to be 0.007 +/- 0.005 and 0.82 +/- 0.43 m(2) g(-1), respectively. Our analysis shows that the MAE of POM can be biased high by up to 50% if absorption from internal mixing of POM and BC is not included.