Appraisal of regional haze event and its relationship with PM2.5 concentration, crop residue burning and meteorology in Chandigarh, India

Abstract Air pollution affects not only the air quality in megacities but also in medium and small-sized cities due to rapid urbanization, industrialization, and other anthropogenic activities. From 28th October 2015 to 3rd November 2015, the Indo-Gangetic Plains region, including Chandigarh, encountered an episode of poor visibility during the daytime. The daily average PM2.5 concentration reached 191 μg/m3, and visibility reduced by ∼ 2.2 times in the Chandigarh region. PM2.5 concentration was found around 4 times higher than a non-haze day and more than 3 times higher than National Ambient Air Quality Standards for 24 h. A significant correlation between PM 2.5 and CO (r: 0.87) during the haze period indicating similarity in their emission sources can be attributed to the burning of organic matter. Further, satellite data and back-trajectory analysis of air masses show large-scale rice stubble burning in the agricultural fields in the city's adjoining areas. The transboundary movement of air masses below 500m and meteorological conditions played a major role in building the pollution load in the Chandigarh region. Moreover, the enhanced concentration of biomass burning tracers, i.e., organic carbon (∼3.8 times) and K+ ions (2∼ times) in PM2.5 and acetonitrile (∼2.3 times) in ambient air was observed during the haze event. The study demonstrates how strongly regional emissions can affect meteorological conditions and air quality in a city; thiscan be useful for proper planning and mitigation policies to minimize high air pollution episodes.