Aerosol and trace gas studies at Pune during INDOEX IFP-99

Ground-based measurements of aerosols and trace gases were carried out at Pune during January-March 1999 under INDOEX IFP-99, to study the physical and chemical characteristics of aerosols, the level of pollutants and their formation mechanisms. Total suspended particulates (TSP) were collected using high volume sampler, the mass size distribution of aerosols was measured using a multistage Andersen sampler, trace gases (SO2, NO2, NH3) by using wet scrubbing method and surface ozone, using UV photometric ozone analyser. The analysis of the data revealed that during the winter months (January and February), TSP concentrations were less compared to those in the beginning of summer (March), High concentrations of TSP in March may be due to the increased convective activities. The mass size distribution of aerosols showed bimodal distribution with one peak in fine size (< 1 mum radius) and another in coarse size. The contribution of coarse and fine particles to the total aerosol mass was more or less same in January, whereas coarse particles dominated in March. The chemical composition of water soluble aerosols showed that even though the concentrations of acidic components (SO4 and NO3) were high, they were being neutralized by alkaline components such as NH4, Ca, K and Mg. Hence, the aerosols are still in the alkaline range. On an average, the concentration of trace gases (SO2, NO3, O-3 and NH3) are within the world background values, however, on some occasions, the SO2, NO2 and O-3 concentrations have exceeded.