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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.

The highly populated Indian regions are currently in a phase of rapid economic growth resulting in high emissions of carbonaceous aerosols. This leads to poor air quality and impact on climate. The chemical composition of carbonaceous aerosols has rarely been studied in industrial areas of India. Here, we investigated carbonaceous aerosols in particulate matter (PM) monthly in the industrial area of Delhi in 2011. The concentrations of organic C and elemental C in PM10 fraction were analyzed. Results show a clear seasonal variability of organic and elemental C. PM10 ranged 95.9–453.5 μg m−3, organic C ranged 28.8–159.4 μg m−3, and elemental C ranged 7.5–44.0 μg m−3; those values were higher than reported values. Organic and elemental C were correlated with each other in pre-monsoon and winter seasons, implying the existence of similar emission sources such as coal combustion, biomass burning and vehicular exhaust. The annual average contribution of total carbonaceous aerosols in PM10 was estimated as 62 %.