Seasonal variation and sources of aerosol pollution in Delhi, India

Abstract

Urbanization and industrialization in Delhi are growing very rapidly. As a consequence, aerosol emissions are increasing, thus leading to poor ambient air quality for human health. The precise sources and chemical composition of carbonaceous aerosols are not well known. In India, carbonaceous aerosols represent a major part, of around 50 %, of PM2.5: the particulate matter with aerodynamic diameter lower than 2.5 µm. Here, we investigated carbonaceous aerosol in PM2.5 fraction monthly in the industrial area of Delhi in 2011. Results show annual average concentrations of PM2.5 of 145.59 µg/m3, of organic C of 41.12 µg/m3 and of elemental C of 13.25 µg/m3. Organic C and elemental C were higher in post-monsoon and winter seasons. Organic and elemental C were correlated in pre-monsoon with R 2 of 0.83, and in winter with R 2 of 0.79, implying the existence of similar emission sources. The organic/elemental C ratios in PM2.5 ranged from 2.71 to 5.29 with an annual average of 3.28, indicating that vehicle exhaust, coal smoke and biomass burning are the sources of carbonaceous fractions in Delhi.