Impact of anthropogenic emissions and open biomass burning on carbonaceous aerosols in urban and rural environments of Indo-Gangetic Plain

Carbonaceous aerosols were studied at two locations, urban and rural, on day and night time basis for 1 year in the Indo-Gangetic Plain. Average OC and EC concentrations at the urban site were observed as 25.6 and 13.7 μg/m3, while at the rural site as 29.6 and 12.8 μg/m3. Exceptionally high OC and EC values were observed during November indicating the impact of large-scale open biomass burning, in the post-harvesting season, on carbonaceous aerosols in the region. The high OC and EC levels were observed during the winter season and low during the monsoon season. Estimated secondary organic carbon accounted for 44.4 and 39.5 % of OC at the urban site and 58.3 and 35.6 % of OC at the rural site during day and night time, respectively. A good correlation was observed between OC and EC indicating a common origin of these species at both the sites. OC/EC ratios mainly in the range 1–4 at the urban site suggested the influence of motor vehicle exhaust as the main emission source whereas at the rural site, an occurrence of OC/EC > 4 indicated the impact of residential wood smoke and biomass burning. PM2.5 samples were analyzed for eight individual carbon fractions (OC1, OC2, OC3, OC4, EC1, EC2, EC3, and OP). Principal component analysis of eight carbon fractions indicated the influence of anthropogenic emissions at both the sites.