Variation of Quasi‐Ultrafine Particle Concentrations During Odd–Even Traffic Restrictions in Delhi

ABSTRACT The transportation sector is one of the major potential contributors to air pollution in urban regions, which is more harmful to human health. The concentration of quasi‐ultrafine particles is found to be higher in terms of number concentration but lower in terms of mass concentration. Delhi is known for its frequent pollution events, and various mitigation measures have been implemented over time to reduce the pollution load. The odd–even scheme for vehicular movement is one among several mitigation measures introduced for the third time in Delhi. Particle number concentration (PNC) variation during the implementation of the scheme was measured and analyzed in three major locations: Najafgarh, Pitampura, and Panchkuian. The study revealed that the quasi‐ultrafine PNC was reduced by around 30.4%, 30%, and 28.4%, respectively, in all three monitoring locations. The total vehicle count (TVC) showed a 26.7% reduction on odd days and a 24.9% reduction on even days, whereas reductions of 27.4% and 24.8% occurred in cars and taxis, respectively, for both odd and even days. In all locations, the concentration reduction obtained was greater on the odd days compared to the even days. Introducing such schemes will be beneficial in mitigating air pollution during extreme events, and source‐specific actions are necessary to achieve and maintain good air quality in the long run.