Quantifying the sources of anthropogenic aerosols over western India

Anthropogenic aerosols significantly deteriorate the urban air quality and climate of the western Indian region, nevertheless, the contributions from different sources (power, residential, transport and industries) to ambient particulate pollution has been uncertain. In this regard, high-resolution simulations have been conducted employing the WRF-Chem (v3.9.1) model to comprehensively assess contribution from major anthropogenic sources in post-monsoon (November 2019), when air quality is typically poor in the region. Model evaluation is conducted by comparing simulated near-surface aerosol concentrations (PM_2.5 and PM₁₀) and aerosol optical depth (AOD) against ground-based measurements (CPCB), satellite data (MODIS), and the reanalysis dataset (MERRA-2). The results show that the model captures the spatial distribution of AOD satisfactorily, with WRF-Chem simulated AOD (0.38 ± 0.10) aligning well with MERRA-2 AOD (0.54 ± 0.10) and MODIS AOD (0.50 ± 0.20). Surface PM_2.5 and PM₁₀ concentrations also meet performance metrics of Fractional Bias ≤ 60% and Fractional Error ≤ 75%, with FAC2 values of 0.9 and 0.7, respectively. Sensitivity analysis reveals spatial heterogeneity in dominant sector that contributes to PM_2.5 concentration over western India. The power sector dominates in most areas with an average contribution of ~14% from regional power sources, followed by regional industries (~12%), regional residential emissions (~9%), and regional transport (~5%). In the trans-regional emissions from the Indo-Gangetic Plain (IGP) and central India also, the power sector remains the largest contributor (~15%), followed by industry (10.5%). Our findings underscore the need for targeted emission reductions in high-impact sectors to improve air quality over western India.