Atmospheric Black Carbon (BC) characteristics over Indore, a data-deficit region in India

Abstract

This study presents a comprehensive characterization of BC pollution over Indore, a data-deficient region in central India. Continuous, year-long real-time measurements using a microAeth were conducted as part of the Clean Air Catalyst (CAC) initiative. These BC measurements were complemented by collocated fine particulate matter (PM_2.5) and Carbon Monoxide (CO), and surface meteorological observations. Highest BC levels were recorded during the winter (5.2 μg m⁻³) and post-monsoon (4.8 μg m⁻³) seasons, while the monsoon season registered the lowest concentrations (1.9 μg m⁻³). Fossil fuel combustion was the dominant source, contributing approximately 84 % of the BC mass, while biomass burning accounted for 16 %. BC comprised around 6–12 % of the PM_2.5 across different seasons. About 70 % of the observed BC originated from local emission sources, primarily due to vehicular and industrial activities. A comparison of MERRA-2 reanalysis BC data with in-situ measurements revealed significant underestimation by MERRA-2 and a low temporal correlation (r = 0.34). These findings (i) support the adoption of evidence-based air pollution mitigation plans by city administrations, (ii) highlight the need for both city-level and regional scale mitigation efforts, (iii) underscore the inadequacy of global reanalysis datasets in capturing urban BC dynamics in central India, and (iv) advocate for long-term ground-based BC monitoring to inform regional emission inventories and assess the effectiveness of mitigation strategies.