Characterization and reconstruction of aerosol light scattering coefficient at chengdu during biomass burning and dust storm period in spring

Aerosol samples for PM_2.5 were collected from 19 April to 17 May in 2009 at Chengdu. The concentrations of organic carbon, element carbon, water-solubility ions, crustal elements and levoglucosan of all particle samples were determined by thermal/optical carbon analyzer, ion chromatography, X-ray fluorescence spectrometer and high performance anion exchange chromatography, respectively. In-situ scattering coefficients (b_sp) and meteorological parameters for this period were also conducted. Ambient scattering coefficients were reconstructed by IMPROVE formula and compared with measured scattering coefficients. The results showed that the average mass concentration of PM_2.5 and measured b_sp were 133.2 μg·m^-3 and 530 Mm^-1, respectively. Levoglucosan and crustal elements were good traces for biomass burning and dust storm events, respectively. The calculated b'_sp was 504 Mm^-1 during campaigning period. The major contributors to scattering coefficients included: (NH₄)₂SO₄ (26%), NH₄NO₃ (15%), OM (53%), FS (4%) and CM (2%), respectively. The calculated b'_sp was 575 Mm^-1 and the dominant species were FS (17%) and CM (21%) during dust storm period (DS). The calculated b'_sp was 635 Mm^-1 and OM contributed 62% during biomass burning (BB) period.