Characteristics of mass distributions of aerosol particle and its inorganic water-soluble ions in summer over a suburb farmland in Beijing

Agricultural activity is one of the important sources of aerosol particle. To understand the mass distribution and sources of aerosol particle and its inorganic water-soluble ions in the suburb farmland of Beijing, particle samples were collected with a MOUDI cascade impactor in the summer of 2004 in a suburb vegetable field. The mass distributions of the particle and its inorganic water-soluble ions in the diameter range of 0.18-18 μm were measured. The dominant ions in the fine particle were SO₄^2-, NO₃^- and NH₄⁺. The association of day to day variation of the concentration of these ions with temperature, humidity and solar radiation suggests that they are formed by the reaction of NH₃ released from the vegetable field with the acid species produced from photochemical reactions. K⁺ in the fine particle is likely from the vegetation emission and biomass burning. Ca²⁺, Mg²⁺, NO₃^- and SO₄^2- in the coarse particle are suggested to come from the mechanical process by which the soil particle entered the atmosphere, and from the reactions of the acid species at the surface of the soil particle. The results show that fertilizer and soil are possibly important factors determining the aerosol particle over the agricultural fields, and the vegetable fields in suburb Beijing could contribute significantly to the aerosol particle.