A campaign-based study on the physio-chemical characterization and source apportionment of particulate matter in the...

This study presents the first campaign-based assessment of the physio-chemical characteristics, sources, and health risks of particulate matter (PM_2.5 and PM₁₀) across Uttarakhand state in the Central Himalaya, India. Spanning 13 districts across diverse geographical features during winter and summer with a low volume PM sampler, the research integrates advanced analytical techniques (XRD, SEM-EDX, ICP-MS) with receptor modeling (Positive Matrix Factorization) and health risk assessment. Results reveal significant spatial and seasonal variability: PM_2.5 (20-125 µg/m³) and PM₁₀ (25-190 µg/m³) concentrations frequently exceeded WHO guidelines, with higher PM_2.5/PM₁₀ ratios (0.48-0.72) in winter indicating anthropogenic dominance, while summer showed stronger crustal influences. Aerosol optical depth (380-1020 nm) was lower at high-altitude sites (0.24-0.46), with spectral anomalies at 936 nm highlighting absorbing aerosols (e.g., black carbon, mineral dust). Mixed aerosols (58%) dominated over dust (18%) and biomass burning (7%). XRD identified carcinogenic quartz and hematite, alongside crustal and industrial minerals (kaolinite, gypsum, calcite etc.). SEM-EDX revealed diverse particle morphologies, with C, O, Si, and Al as dominant elements. PMF source apportionment (ICP-MS) traced PM₁₀ primarily to mineral dust (41.7%) and combustion activities (34.5%), and PM_2.5 to biomass burning (12.3%) and dust (51.1%). Enrichment factors and health risk assessments indicated potential non-carcinogenic risks (especially for children) from Cd and Al, and carcinogenic risks from Cr. This study highlights the need for targeted mitigation strategies and future research, incorporating a wider range of PM constituents (ions, carbonaceous aerosols, PAHs, trace gases) for a comprehensive understanding of aerosol impacts in the region.