Seasonal Variation in Contribution of Local Anthropogenic Emissions vs Long-Range Transport in Urban Environment

Air quality of mega-cities specially in developing countries are consistently reported to be poor over the past few years with average values of criteria pollutants often exceeding the prescribed national standards.. In general the high pollution scenario is believed to be associated to high emissions in the region. Apart from local emission sources, air quality of a given region also depends on medium-range and long-range transport of pollutants (both natural and anthropogenic) from neighboring and distant areas respectively. In order to devise a smarter pollution control strategy, in-depth knowledge of relative contribution of various sources to the resulting pollution in the region of interest is necessary. High intra-seasonal as well as inter-seasonal variability in the pollutant concentration over Delhi –NCR makes it a suitable study area.

Delhi is the capital city of India and the largest city by area and second largest by population in India. It is the eight largest mega-city in the world with more than 18 million inhabitants

Atmospheric chemical transport models provide unique opportunity to study the contribution of these sources to the pollutant concentrations in a given region of interest. In this study, a 3D Eulerian atmospheric chemical transport model CMAQ has been used in order to quantify the contribution of local and remote anthropogenic emission sources to the Ambient air quality of Delhi-NCR. Analyses for CO, NO2, NO, SO2, VOCs, PM10 and PM2.5 have been performed for contrasting seasons. It has been found that high emission flux from vehicular, industrial and construction activities dominates the air quality of Delhi with occasional dominance of remote sources. The details of these contributions will be presented This study could help in formulating robust species-wise and season-specific emission-reduction strategies for policymakers.