Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2016-1060
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
07 Dec 2016
Review status
A revision of this discussion paper was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.
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 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 important impact on the global radiative budget. A better understanding of the mixing state and chemical composition of biomass burning particles relative to their optical properties is the goal of a number of current studies. In this work, effective density, chemical composition, and optical properties of rice straw burning particles in the size range of 50–400 nm were measured using a suite of comprehensive methods. A Differential Mobility Analyzer (DMA)-Aerosol Particle Mass analyzer (APM)-Condensation Particle Counter (CPC) system offered detailed information on the effective density as well as mixing state of size-resolved particles. The effective density and chemical composition of individual particles were characterized with a DMA in-line with a Single Particle Aerosol Mass Spectrometer (SPAMS), simultaneously. The multiple modes observed in the size-resolved particle effective density distribution indicated size-dependent external mixing of black carbon (BC), organic carbon (OC) and potassium salts in particles. Particles of 50 nm had the smallest effective density (1.16 g/cm3), due to a relative large proportion of aggregate BC. The average effective densities of 100–400 nm particles ranged from 1.35–1.51 g/cm3 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 testified the existence of less volatile BC or soot and potassium salts. Size-resolved optical properties of biomass burning particles were measured by the Cavity Attenuated Phase Shift spectroscopy (CAPS, λ = 450 & 530 nm). The single scattering albedo (SSA) showed the lowest value for 50 nm particles (0.741 ± 0.007 & 0.889 ± 0.006) because of larger proportion of BC content. Brown carbon played an important role for the SSA of 100–400 nm particles. The Ångström absorption exponent (AAE) values for all particles were above 1.6, indicating the significant presence of brown carbon. Though freshly emitted, the light absorption enhancement (Eabs) was observed for particles larger than 200 nm. Concurrent measurements in our work provide a basis for discussing the physicochemical properties of biomass burning aerosol and its effects on global climate and atmospheric environment.

Citation: Zhai, J., Lu, X., Li, L., Zhang, Q., Zhang, C., Chen, H., Yang, X., and Chen, J.: Size-resolved chemical composition, effective density, and optical properties of biomass burning particles, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1060, in review, 2016.
Jinghao Zhai et al.
Jinghao Zhai et al.

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