Impact of meteorological parameters on the development of fine and coarse particles over Delhi.

Measurements of ambient particulate matters (viz., PM10 and PM2.5) were made with an hourly sampling frequency at Indian Institute of Tropical Meteorology (IITM), New Delhi Branch (a residential area) during a period from December 2010 to November 2011. The data so generated were analyzed to understand frequency distribution of their concentrations and the impact of meteorological parameters on the distribution of particulate matters on different time scales. It is found that the particulate matters with cut off aerodynamic diameter of 10 μm (PM10) preferentially occurred in the concentration range of 301-350 μg/m(3) during winter and post-monsoon, 251-300 μg/m(3) during summer and 51-100 μg/m(3) during monsoon season. The particulate matters with cut off aerodynamic diameter of 2.5 μm (PM2.5) preferentially occurred in the concentration range of 201-250 μg/m(3) during winter and 51-100 μg/m(3) during the remaining seasons. The concentration of particulate matters (PM10 and PM2.5) remained always above the National Ambient Air Quality Standards (NAAQS) except during monsoon season. Annual distribution of the concentration of particulate matters showed seasonality with maximum in winter and minimum in monsoon season. Diurnal variation of PM10 and PM2.5 showed bimodal distribution with one maximum in the forenoon and the other at around mid-night. The observed seasonality and diurnal variability in the distribution are attributed mainly to the meteorology.