Optical-microphysical and physical-chemical characteristics of Siberian biomass burning: Experiments in Aerosol Chamber.

A series of experiments aimed at studying the effect of combustion regimes of typical Siberian biomasses on the optical, microphysical, and physical-chemical properties of smoke aerosols was performed in the Large Aerosol Chambe, Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences. A comprehensive data analysis showed that temperature regime of Siberian pine and coniferous tree burning has a key effect on the formation and time dynamics of all smoke characteristics. The polarization spectronephelometer measurements of light scattering are used to determine the size distributions and absorption indices of particles. Particles in the smoldering phase are weakly absorbing, but the mixed phase contains a strongly absorbing fine component produced in open flame phases. We studied microstructure characteristics of aerosols by the analysis of morphology and elemental composition. Groups of soot and organic particles were determined as micromarkers of emissions in open flaming and smoldering phases, respectively. The organic and elemental carbon contents, origin and concentration of chemical compounds in the water-soluble ion fraction exhibit a strong dependence on the combustion phase. Sugar anhydride (levoglucosan) was determined in the smoldering phase as a stable molecular marker of Siberian pine burning. A number of specific markers of coniferous wood burning were identified among the chemical compounds. Smoke aging is accompanied by condensation of organic and inorganic compounds, transformation of aerosol surface chemistry, and the formation of the group of potassium-rich particles, all demonstrating the complexity and variability of the chemical composition and microstructure of atmospheric aerosol pollution during Siberian forest fires