Implications of equivalent black carbon heterogeneity in south Indian high-altitude eco-sensitive region

Large-scale representative source apportionment studies are uncommon, undermining source contribution studies in India, particularly in high-altitude locations. Kodaikanal is a high-altitude region in India's Western Ghats, with spatial heterogeneity of sources altering chemical complexity; thus, the associated implications are unknown. We conducted the campaign study REBER (Research on Equivalent Black Carbon Monitoring in an Eco-sensitive Region) at three Kodaikanal sites to understand local point sources, characteristics, and distribution of eBC during the winter-to-summer monsoon transition. For two main reasons: to understand the seasonal change of BC since the transition period has the lowest wind speeds and the highest particulate concentrations and is prone to high pollution events most often during seasonal transition months, and to study local pollution since the meridional monsoon and zonal winds in study region weaken whereby the transport of pollutants from ocean to land and vice versa is minimal. The results showed that the eBC mass concentration was 85% higher than in the previous study conducted by Bhaskar et al. (2018) during the monsoon transition period. To determine the ratio of fossil fuel and wood-burning sources, a real-time apportionment model of atmospheric eBC is used. The percentage of wood burning in the background location ranges from 21.12 to 88.98%. Wood burning leads in residential sites with 57.5 ± 7.3%, whereas fossil fuel contribution dominates traffic sites with 69.84 ± 10.2%. Fossil fuel contributions are significant in different characteristics of environments, ranging from 42.5 to 69.84%. The results of the conditional bivariate probability function (CBPF) analysis pointed out a competition between anthropogenic and natural sources to contribute as local sources to the monitoring stations. A scanning electron microscope (SEM) paired with an energy dispersive X-ray (EDX) analysis found that the particle size was 93% relatively large compared to other hill stations in India. The variation in the chemical constituents indicates that the particles originated from various sources.