Seasonal variation of carbonaceous species in PM1 measured over residential area of Delhi, India

Abstract

Seasonal variation in the concentration of Organic Carbon (OC) and Elemental Carbon (EC) was investigated in PM1 size fraction over a residential area in Delhi, India. The sampling was carried out using a cascade impactor from April 2018 to March 2019. The OC/EC content in the sample was measured by a carbon analyzer (Thermal/Optical, DRI 2001). The annual average concentration of OC and EC was found to be 28.01 ± 14.61 μg/m3 and 10.40 ± 7.41 μg/m3, respectively in PM1 (139.52 ± 49.20 μg/m3). The highest concentrations of OC and EC were observed in the post-monsoon and winter season, respectively. Average OC & EC concentrations in summer, monsoon, post-monsoon, and winter seasons were found to be 22.57 ± 3.72 & 5.51 ± 1.28, 11.70 ± 3.07 & 3.60 ± 0.39, 42.06 ± 7.10 & 11.72 ± 2.45 and 37.28 ± 14.45 & 18.52 ± 6.23 µg/m3, respectively. Total carbonaceous material (TCM) accounted for approximately 40% of PM1 concentration. The annual average OC/EC ratio was observed to be 2.69, which ranged between 1.77 to 5.39. Analysis of carbon subfractions reveals OC3 and EC1 as the dominant fraction suggesting fossil fuel combustion as dominant emission sources. The exposure risk estimated on the basis of inhalation dose was observed very high during the winter season which can adversely affect the health of people. This study also revealed that the emissions from the residential area are the key source of OC and EC, along with PM1.