Retrieval of satellite-derived black carbon concentration and mitigation approaches for Karnataka, India

Abstract

Black carbon (BC) is a short-lived climate pollutant that adversely impacts human health, regional air quality, and climate. Accurate monitoring of its spatiotemporal variability remains a challenge due to limited ground-based observations. This study develops a high-resolution (1 × 1 km) dataset of annual BC columnar concentrations across Karnataka, India, for 2018–2024 by combining satellite retrievals of aerosol optical depth (AOD), carbon monoxide (CO), and nitrogen dioxide (NO₂) with ground-based BC observations using regression modeling. Results show a consistent rise in annual BC concentrations of 0.2–0.5 μg/m³ per year, except in 2020 when emissions decreased due to pandemic-related restrictions. District-level analysis identifies Kalaburagi, Raichur, Ballari, Bengaluru Urban, and Vijayanagara as major BC hotspots. Sectoral contributions indicate Industry (46.4 %) and Road Transport (39.8 %) as dominant sources, with smaller shares from Residential (6.8 %), Forest Fires (3.5 %), Stubble Burning (2.4 %), and miscellaneous activities (1.2 %). Model evaluation demonstrates moderate agreement between estimated BC and independent datasets, with R² = 0.65 and RMSE = 0.49 against ground-based measurements, and coefficient of determination (R²) = 0.57 and Root Mean Square Error (RMSE) = 0.66 compared to Modern-Era Retrospective Analysis for Research and Applications (MERRA-2) reanalysis data for 2024. The high-resolution BC maps and hotspot and sectoral analyses provide improved spatial detail compared to reanalysis products or chemical transport models. These results highlight the growing BC b urden in Karnataka, the need for targeted mitigation in industrial and transport sectors, and the value of satellite-based approaches in supporting evidence-based air quality and climate policies.