Spatial, temporal and source study of black carbon in the atmospheric aerosols over different altitude regions in Southern India

Abstract

Ambient equivalent black carbon (EBC) aerosol mass concentration is regularly observed over a period of 2 years (June 2014 to May 2016) at Kodaikanal, a high-altitude and Madurai, a semi-arid location to study its spatial and temporal characteristics and its sources. The diurnal variation of EBC had two peaks, early morning sharp peak that occurred between 06:00 and 09:00 h (LT) almost an hour after the local sunrise and the evening broad peak that occurred between 19:00 to 22:00 h (LT), while in Kodaikanal late afternoon peaks showed maximum contribution. The difference in the sunshine hours with respect to seasons also caused an effect on the EBC concentration. The mean seasonal values of EBC over Kodaikanal are 2.58 ± 0.15 μg m−3, 1.98 ± 0.19 μg m−3, 1.01 ± 0.19 μg m−3 and 2.48 ± 0.15 μg m−3 and over Madurai 8.97 ± 2.34 μg m−3, 4.69 ± 2.14 μg m−3, 6.70 ± 3.83 μg m−3 and 3.34 ± 2.53 μg m−3 during winter, summer, monsoon and post-monsoon seasons, respectively. The effects of meteorological parameters on EBC at the two stations are investigated and it is found that wind speed and rainfall plays a major role. Source identification is done by calculating absorption Angstrom exponent (α). The absorption Angstrom exponent values ranged from 0.99 to 1.15 with the average value of 1.05 for Madurai and a range from 0.54 to 1.92 with an average value of 1.43 for Kodaikanal, indicating that the major sources of EBC on the study site are from biomass burning and fossil fuel burning sources.