ABSTRACT
Daily, monthly, seasonal and annual moving means of PM1, PM2.5 and PM10 concentrations from August, 2007 to October, 2008 at Delhi (28� 35' N; 77� 12' E), the seventh populous megacity in the world are presented. PM1, PM2.5 and PM10 concentrations varied seasonally with atmospheric processes and the anthropogenic activities. PM10 decreases during monsoon by ~25-80 �g m-3 and PM1 and PM2.5 by ~10-15 �g m-3 from their pre-monsoon levels. Emissions from fireworks during Deepawali in the post-monsoon season increases PM1, PM2.5 and PM10 levels by 300, 350 and 400 �g m-3, respectively over their monsoon levels. Seasonal variation of mixing heights, temperatures, winds and rainfall, accounts for the inter-annual variability of PM1, PM2.5, and PM10. Accordingly, wintertime PM1, PM2.5 and PM10 components contribute by ~30-33% to annual levels. PM10 in summer is higher by 8% to that of PM2.5 and by 9% to that of PM1. PM10 components in post-monsoon are lower by 5% to that of PM2.5 and by 7% to that of PM1. Also, PM1, PM2.5 and PM10 levels were higher during October, 2008 than those in 2007, but their levels were almost remain the same in August and September of 2007 and 2008. Moving means of PM1, PM2.5 and PM10 and their concentrations in different seasons are useful in policy making decisions thereupon aiming to improve the air quality in Delhi
