Spatial-Temporal Variability and Characterisation of Aerosols in Urban Air Quality of Ahmedabad, India, based on Field and Satellite Data

Particulate matter (PM), or aerosol play an important role in Air Quality. Ahmedabad is an urban, industrialized and one of the fastest growing city in Western India. This study presents spatio-temporal variability in mass concentrations of different Particulate Matter as well as their characteristics during different seasons based on field measurements in different micro urban environments of Ahmedabad. The meteorological parameters such as wind speed, temperature, relative humidity and atmospheric pressure played a very important role in the seasonal variation of the PM concentrations. The PM 10 , PM 2.5 and PM 1 were found to be highest with 229.4 g/m 3 , 82.20 g/m 3 and 53.53 g/m 3 , respectively in winter season. These PM concentrations are higher than the National Ambient Air Quality Standard (NAAQS) for PM 10 and PM 2.5 . The aerosol characteristic based on field measurement of spectral Aerosol Optical Depth indicates significant contribution by coarser mode particles. The Inhalable, Thoracic and Alveolic PM concentrations which are significant for human health impacts of ambient air quality were observed in the increasing order of monsoon<summer<winter seasons. It is interesting to note that rainfall play a scavenging effect only on the coarser particles with mean PM 1 values lowest in summer season (20.4 g/m 3 ) as compared to PM 2.5 and PM 10 which are lowest during monsoon season. Vertical profile of aerosols from spaceborne Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) indicated a predominance of polluted dust type aerosols over the study area at height of 3-4 km which is important constituent of inhalable air of resident population. The results of this study may serve as important inputs for policy makers for formulating action plans and improving air quality by adopting suitable air pollution control measures in fast urbanising environment.