A chemical characterization of atmospheric aerosol in Sapporo

Monthly mean chemical composition of aerosol with diameter less than 8 μm was identified in Sapporo in 1982. The mass of aerosol was made up of nine components: elemental C, organics, SO42−, NO3−, NH4+, Cl−, Na+, soil particles and water. The concentrations of carbonaceous particles (elemental C and organics) was relatively high (12.7–16.0μ m−3) in autumn and winter (October–February) due to emission from domestic heating and comprised 36–41% of total aerosol mass. Higher concentration of soil particles was observed in spring (March–May) (9.7–13.1 μg m−3) and comprised 22–29% of total aerosol mass due to suspension by strong wind. On the other hand, the concentration of excess SO42− (non-sea salt SO42−), which ranged from 2.6–5.2 μg m−3, did not change remarkably with season, and the fraction of excess sulfate increased to 21% in summer (July–August) probably due to photochemical transformation from SO2. Nitrate concentration was far less than that of SO42− throughout the year in Sapporo.