Study on Ambient Air Quality of Megacity Delhi, India During Odd–Even Strategy

State Government of Delhi had adopted odd – even scheme on vehicles plying in megacity Delhi to understand and improve the air quality of Delhi. To understand the effect of odd–even scheme on the concentration of pollutants, we have analysed the concentrations of chemical constituents [organic carbon, elemental carbon, water soluble inorganic components, trace elements and stable carbon and nitrogen isotopic composition (δ 13 C TC ) and N (δ 15 N TN )] of PM 2.5 and PM 10 along with mixing ratios of trace gases (NO x , CO, SO 2 and NH 3 ) data collected at an urban site of megacity Delhi during first phase (Phase-I: winter 2016) and second phase (Phase-II: summer 2016). During the Phase-I of the scheme, mass concentrations of PM 2.5 and PM 10 were changed by −13 and −5%, respectively, whereas, concentrations of PM 2.5 and PM 10 were changed by +18 and +16%, respectively during the Phase-II as compared to before the implementation of the scheme. The analysis of chemical constituents of PM 2.5 and PM 10 reveals that the odd–even strategy marginally changed the concentrations (markers) of vehicular emission. During both the phases, mixing ratios of trace gases (NO x , CO, SO 2 and NH 3 ) were reduced non-significantly during the odd–even scheme as compared to before the implementation of the scheme.