On processes controlling fine particulate matters in four Indian megacities.

The data of most toxic particulate pollutants (PM and PM) obtained from a dense SAFAR observational network in four Indian mega cities (Delhi, Mumbai, Pune and Ahmedabad) located in North-West part of India, not very far from each other, have been presented in this work. In spite of similar kind of sources of anthropogenic local emissions, each city has its unique air pollution footprints. The paper addresses the role of geographical location based prevailing meteorology in determining the variability of particulate matter in different seasons and processes responsible for the same. We hereby demonstrate that although Delhi has the highest level of particulate matters, the percentage share of PM in PM is highest for Mumbai (60%) as compared to 50% of Delhi. The pollutant levels of Delhi, Mumbai and Pune show strong seasonal variability whereas Ahmedabad does not show any significant variation for summer to winter. We have further discussed that the landlocked geography of Delhi and coastal location of Mumbai often play a dominant role in the distribution of air pollutants. Hence, the mitigation options require specific consideration of integrated approach for each city.