Seasonal Variation of Carbonaceous Species of PM10 Over Urban Sites of National Capital Region of India

Abstract

The air quality of national capital region (NCR) of Delhi, India is becoming more severe day by day because of the anthropogenic activities. To get a better understanding of the ambient air quality of NCR-Delhi, the study of carbonaceous species in particulate matter (PM) is essential. PM10 samples were collected periodically from the three main urban sites (Faridabad; IGDTUW-Delhi; and CSIR-NPL Delhi,) of NCR-Delhi in the year 2015 to explore the possible sources of carbonaceous species [organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC)] in PM10. The annual average concentrations of PM10, OC, EC, and WSOC were estimated as 195 ± 121, 23.6 ± 14.4, 5.2 ± 4.0, and 15.5 ± 7.7 µg m−3, respectively, at Faridabad, whereas average concentrations of PM10, OC, EC, and WSOC were 274 ± 141, 30.8 ± 19.3, 9.4 ± 5.2, and 21.3 ± 14.3 µg m−3, respectively, at IGDTUW, Kashmiri Gate. Concentrations of PM10, OC, EC and WSOC were estimated as 209 ± 81, 26.0 ± 12.8, 7.9 ± 5.6 and 9.7 ± 5.9 µg m−3 at CSIR-NPL. During the study, a significant positive linear trend between OC vs. EC and OC vs. WSOC have been observed for these three sites as (R2 = 0.64 and R2 = 0.76 at Faridabad; R2 = 0.66 and R2 = 0.87 at IGDTUW-Delhi; and R2 = 0.79 and R2= 0.55 at CSIR-NPL), which indicates the common sources (vehicular emission and/or biomass burning) of carbonaceous aerosols over NCR-Delhi. All these carbonaceous species of PM10 shows seasonal variation with maxima during winter as well as post-monsoon and minima during monsoon seasons. 5 days backward trajectories of the air masses were calculated which shows the origination of pollutants from local sources along with long-range transport. Furthermore, the secondary and primary organic carbon (i.e., SOC and POC) in PM10 were also computed and reported.