Influence of Fossil Fuels on Carbonaceous Aerosols: A Comparison among Urban Locations in India

Abstract

The organic carbon (OC) and elemental carbon (EC) were characterized in different urban regions and categorized by diverse predominant sources. This study investigates seasonal and interlocation variability of OC and EC concentration and their role in light extinction coefficient (b_ext) in Indian cities. OC and EC exhibit significant spatial variability (p < 0.05) with high loading of EC at Delhi (20.80 ± 5.30 µg m^− 3) followed by Hyderabad (12.18 ± 4.96 µg m^− 3) and Pune (10.36 ± 4.77 µg m^− 3) while OC was abundant at Jabalpur (50.24 ± 4.23 µg m^− 3) followed by Udaipur (49.56 ± 6.46 µg m^− 3). The total carbonaceous aerosols (TCA) was the highest at Delhi (Mean = 87.42 ± 53.44 µg m^− 3) along with EC (Mean = 20.80 ± 5.30 µg m^− 3), followed by Hyderabad (TCA: 48.37 ± 25.50 µg m^− 3 and EC: 12.18 ± 4.96 5.30 µg m^− 3). The lowest TCA was found to be at Pune (TCA: 43.36 ± 25.60 µg m^− 3 and EC: 5.75 ± 5.46 µg m^− 3). Fractional EC percentage contribution to TC in Delhi is 10–15% higher than in other locations; in contrast, fractional OC percentage share in TC is lower by 20% relative to Jabalpur. Such an occurrence is attributable to relatively high combustion in Delhi and high secondary organic carbon (SOC) in Jabalpur. Fossil fuel combustion (FFC) was an ample source of OC and EC in Delhi compared to other locations, while SOC was the most abundant source in Jabalpur. It was found that FFC source was predominant, influencing carbonaceous species in urban regions of India. The OC and EC concentrations exhibited prominent seasonal variability, with the highest values during winter followed by post-monsoon, pre-monsoon, and lowest during monsoon. OC and EC showed a significant correlation (R²: 0.78 − 0.55) at all the locations, while primary organic carbon (POC) had an insignificant relationship with SOC (R²: 0.02–0.24). The average aerosol light extinction coefficient (b_ext) showed substantial spatial variability with the highest values at Delhi (913 ± 485 Mm^− 1) followed by Jabalpur (584 ± 308 Mm^− 1) and the lowest at Pune (451 ± 275 Mm^− 1). The analysis indicates that carbonaceous species have a dual nature: they are a more absorbing type in Delhi and a more scattering type in Pune.