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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 17, issue 12 | Copyright
Atmos. Chem. Phys., 17, 7481-7493, 2017
https://doi.org/10.5194/acp-17-7481-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 21 Jun 2017

Research article | 21 Jun 2017

Size-resolved chemical composition, effective density, and optical properties of biomass burning particles

Jinghao Zhai1, Xiaohui Lu1, Ling Li1, Qi Zhang1,2, Ci Zhang1, Hong Chen1, Xin Yang1, and Jianmin Chen1 Jinghao Zhai et al.
  • 1Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China
  • 2Department of Environmental Toxicology, University of California, Davis, California 95616, USA

Abstract. Biomass burning aerosol has an important impact on the global radiative budget. A better understanding of the correlations between the mixing states of biomass burning particles and their optical properties is the goal of a number of current studies. In this work, the effective density, chemical composition, and optical properties of rice straw burning particles in the size range of 50–400nm were measured using a suite of online methods. We found that the major components of particles produced by burning rice straw included black carbon (BC), organic carbon (OC), and potassium salts, but the mixing states of particles were strongly size dependent. Particles of 50nm had the smallest effective density (1.16gcm−3) due to a relatively large proportion of aggregate BC. The average effective densities of 100–400nm particles ranged from 1.35 to 1.51gcm−3 with OC and inorganic salts as dominant components. Both density distribution and single-particle mass spectrometry showed more complex mixing states in larger particles. Upon heating, the separation of the effective density distribution modes confirmed the external mixing state of less-volatile BC or soot and potassium salts. The size-resolved optical properties of biomass burning particles were investigated at two wavelengths (λ = 450 and 530nm). The single-scattering albedo (SSA) showed the lowest value for 50nm particles (0.741±0.007 and 0.889±0.006) because of the larger proportion of BC content. Brown carbon played an important role for the SSA of 100–400nm particles. The Ångström absorption exponent (AAE) values for all particles were above 1.6, indicating the significant presence of brown carbon in all sizes. Concurrent measurements in our work provide a basis for discussing the physicochemical properties of biomass burning aerosol and its effects on the global climate and atmospheric environment.

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The effective density, chemical composition, and optical properties of particles produced by burning rice straw were measured. Density distribution and single-particle mass spectrometry showed the size-dependent external mixing of black carbon, organic carbon, and potassium salts in biomass burning particles. Optical measurements indicated the significant presence of brown carbon in all particles. Though freshly emitted, light absorption enhancement was observed for particles larger than 200 nm.
The effective density, chemical composition, and optical properties of particles produced by...
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