Black carbon pollution over India simulated with recent emission inventories and WRF-CHEM model

Abstract

This study simulates the BC concentrations in India using the WRF-Chem model with four emissions inventories: Expt-I (Constrained emissions), Expt-II (SMOG-India), Expt-III (EDGAR-HTAP V3), and Expt-IV (Mix), emphasizing on two domains, the whole Indian region (D01) and the Indo-Gangetic Plains (IGP) (D02). The simulated BC over D01 was 2–3 times higher using Expt-I compared to Expt-II and Expt-III, despite the similar spatial-seasonal variations. BC simulations from Expt-I show good agreement with observed data, particularly at megacities like Delhi and Kolkata with high anthropogenic emissions. However, Expt-III underestimates BC concentrations at certain stations, suggesting the need for improvement in emission-inventory strength and proper distribution of emissions. The diurnal BC pattern from Expt-I matches well with measured BC, with higher concentrations during late evening and night hours in the IGP and large cities. High-altitude stations present a BC peak during late afternoon hours due to the transport of pollutants from the IGP within a deeper mixing layer. BC simulations show better agreement during the daytime than nighttime, indicating the effect of nighttime emission strength that needs better representation, while the model underestimations maximize in winter, associated with the highest BC concentrations. Source apportionment analysis revealed the highest contribution from the domestic sector to total BC emissions (58 %) during winter, underscoring the reliance on biofuel combustion for household cooking and heating. The energy and industrial sector contributed significantly to the annual BC levels over the IGP, ranging from 22 % in winter to 28 % in monsoon. The increased contribution from the open burning sector during post-monsoon indicates the effect of crop residue burning in NW IGP. By quantifying BC concentration and identifying its dominant sources utilizing the robust emission inventory, this work provides actionable insights for policymakers and a scientific basis for strategies to mitigate BC pollution and its associated environmental and health impacts.