Effects of black carbon content, particle size, and mixing on light absorption by aerosols from biomass burning in Brazil
Effects of black carbon content, particle size, and mixing on light absorption by aerosols from biomass burning in Brazil
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DOI：
10.1029/98jd02593
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发表时间：
1998-12
影响因子：
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通讯作者：
J. Martins;P. Artaxo;C. Liousse;J. Reid;P. Hobbs;Y. Kaufman
中科院分区：
文献类型：
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作者：
J. Martins;P. Artaxo;C. Liousse;J. Reid;P. Hobbs;Y. Kaufman
在“烟雾、云和辐射-巴西”（SCAR-B）实验中，利用黑碳的热演化测量和光学吸收方法，测量了不同类型生物质火灾中烟雾颗粒的黑碳质量吸收效率。得到的结果范围为5.2 ~ 19.3 m2 g−1，平均值为12.1±4.0 m2 g−1。还测量了粒径分布和光学性质，为建模计算提供了一整套物理参数。采用Mie理论对粒子的光学性质进行了建模，假设粒子的内部和外部混合，并将模型计算与实验结果相结合。对于内部混合，假设粒子模型具有层状结构，由吸收性黑碳核心和非吸收性壳层组成。此外，对于内部混合，使用离散偶极近似代码来模拟在实验期间收集的过滤器的电子显微镜照片中常见的堆积烟灰团。层状球体和填充团簇的模拟结果解释了黑碳质量吸收系数高达约25 m2 g−1的值，但测量结果显示与颗粒的化学成分和结构特征相关的更高值。过高的黑碳吸收效率值与高浓度的K有关，这影响了黑碳（BC）在较低温度下的挥发，可能导致热技术测定BC时出现伪影。模拟结果与浊度计和光吸收测量结果进行了比较。
Black carbon mass absorption efficiencies of smoke particles were measured for various types of biomass fires during the Smoke, Clouds, and Radiation-Brazil (SCAR-B) experiment using thermal evolution measurements for black carbon and optical absorption methods. The obtained results range between 5.2 and 19.3 m2 g−1 with an average value of 12.1±4.0 m2 g−1. Particle size distributions and optical properties were also measured to provide a full set of physical parameters for modeling calculations. Mie theory was used to model the optical properties of the particles assuming both internal and external mixtures coupling the modeling calculations with the experimental results obtained during the campaign. For internal mixing, a particle model with a layered structure consisting of an absorbing black carbon core, surrounded by a nonabsorbing shell, was assumed. Also, for internal mixing, a discrete dipole approximation code was used to simulate packed soot clusters commonly found in electron microscopy photographs of filters collected during the experiment. The modeled results for layered spheres and packed clusters explain black carbon mass absorption coefficients up to values of about 25 m2 g−1, but measurements show even higher values which were correlated with the chemical composition and characteristics of the structure of the particles. Unrealistic high values of black carbon absorption efficiencies were linked to high concentrations of K, which influence the volatilization of black carbon (BC) at lower temperatures than usual, possibly causing artifacts in the determination of BC by thermal technique. The modeling results are compared with nephelometer and light absorption measurements.