Integrated mineral identification of PM using XRD, ATR-FTIR and SEM-EDX techniques in Indo-Gangetic Plain (IGP) and Indo-Himalayan Region (IHR).

The study examines the mineralogical, morphological and elemental characteristics of particulate matter (PM) across the Indo-Gangetic Plain (Delhi and Varanasi) and the Indo-Himalayan region (Nainital) from January to December 2022. PM concentrations showed significant spatial variability, with average loading of 204 ± 86 μg m in Delhi, 197 ± 87 μg m in Varanasi and 68 ± 54 μg m in Nainital. Advanced analytical techniques, including XRD, ATR-FTIR and SEM-EDX, were used for comprehensive characterization of PM. The dominant minerals were identified in PM samples including quartz, dolomite, calcite, albite, illite, montmorillonite and hematite. Geogenic minerals (e.g. quartz, dolomite, and albite) were attributed to natural sources such as rock weathering and dust storms, while anthropogenic contributions (e.g. construction and industrial emissions) were associated with minerals like illite, montmorillonite and hematite. Elemental analysis of PM revealed Si and Al as the most abundant elements, along with Ca, Fe, K, Mg and others at the study sites. ATR-FTIR confirmed the evidence of both inorganic ions (e.g. SO, NO and NH) and organic functional groups, indicating mixed pollution sources. Morphological analysis further distinguished between irregular, geogenic particles, and spherical anthropogenic ones. This study also reveals that Delhi and Varanasi experience high anthropogenic pollution from industrial, vehicular and combustion sources, posing significant health risks from toxic elements like Cr, As and Pb. In contrast, Nainital is primarily influenced by natural sources, but episodic long-range pollutant transport also contributes to health risks, particularly from Mn. Air-mass backward trajectory analysis confirms cross-regional pollution transport, especially from the IGP and surrounding areas. These findings offer key understanding of the composition and origin of PM, providing a scientific basis for improved air quality management in the region.