Chemical composition and size distribution of atmospheric aerosols over the Deccan Plateau, India

Measurements on atmospheric total aerosol were made at Poona during the summer and winter seasons of 1978–79. An Andersen particle sampler Model 20–810, Mark II (Andersen 2000 Inc. U.S.A.) which samples atmospheric particles with diameters ranging between 0.4 and 10.0 µm was used for the measurement. The mass distribution of the total aerosol, and separately for the chloride, sodium, ammonium, sulphate and nitrate components were obtained.

The mass distribution of the aerosols exhibited a bimodal distribution in the size ranges 0.4–0.6 μm and 5–6 μm. The chloride and sodium components exhibited by and large a unimodal distribution. The ammonium and sulphate components exhibited a bimodal distribution during the monsoon and a unimodal distribution during the winter. The nitrate component exhibited a bimodal distribution during the monsoon and winter. The molecular form of this component appears to be ammonium nitrate in the sub-micron range and sodium nitrate in the higher size range (1–10 μm).