Evaluation of spatial and temporal heterogeneity of black carbon aerosol mass concentration over India using three year measurements from IMD BC observation network

Abstract

Extensive measurements of equivalent black carbon (EBC) aerosol mass concentration at fifteen stations of India Meteorological Department (IMD) BC observation network during the period 2016–2018 are used to study the spatial and temporal heterogeneity over India. The sampling sites represent different geographical region of India. Spatial distribution shows higher values of EBC over stations of north India and IGP. Highest annual mean EBC mass concentration during study period was reported at two mega cities New Delhi (13,575 ± 8401 ng/m3) followed by Kolkata (12,082 ± 6850 ng/m3) whereas lowest mean concentration was at Ranichauri (1737 ± 884 ng/m3) followed by Bhuj (2021 ± 1471 ng/m3). Stations located in coastal region of south India reported low concentration of EBC. In order to find out the quantitative contribution of biomass burning (EBCBB) and fossil fuel (EBCFF) in total mass concentration of EBC, source apportionment study has been carried out using Aethalometer model. The EBCFF is the dominant contributor to EBC mass concentration at all the sites in every season, while the highest seasonal biomass burning mass contribution (37%) was observed in the winter at a background site Ranichauri. Maximum concentration of EBCBB was observed at Srinagar (2671 ng/m3) where as EBCFF was maximum in Delhi (11,074 ng/m3). Seasonal and diurnal variation studies have also been carried out for all the stations. The EBC mass concentrations exhibited strong seasonality, with the highest values occurring in postmonsoon/winter and the lowest in monsoon season. The higher EBC concentration in postmonsoon/winter seasons was attributed to the increased use of fuel in seasonal emission sources, domestic heating and stagnant meteorological conditions, whereas the low levels in monsoon season were related to the precipitation scavenging. Maximum concentration of EBC (22,409 ± 10,510 ng/m3) was observed in winter season over Kolkata. Our study finds high spatial heterogeneity in EBC concentrations across the study area.