Physico-chemical characterization of atmospheric particles during two intense dust storms in the vicinity of Thar Desert

Particulate Matter (PM₅; aerodynamic diameter ≤5 μm) was collected over the Jhunjhunu region (28°80′N, 75°24′E) in the neighborhood of the Thar Desert, Rajasthan, India. Sample collection was done during two intense Dust Storm (DS) conditions i.e., DS-1 on May 4, 2022 and DS-2 on May 6, 2022. The physico-chemical properties of dust particles collected pre-, during, and post-DS events were studied using X-ray diffraction (XRD), X-ray Fluorescence Spectroscopy (XRF), and Scanning Electron Microscope coupled with Energy Dispersive X-ray Spectroscopy (SEM-EDS). The frequency distribution of AR (Aspect Ratio) of particles shows bimodal peaks in the bin range >1.6–1.8 and > 2.00–2.20 during DS-1 and monomodal peak at >1.6–1.8 during DS-2, indicating most of the particles are highly non-spherical. Based on bulk compositional analysis of dust particles obtained using XRF, oxides of different elements were observed in the order of SiO₂> Al₂O₃> CaCO₃>MgO > Fe₂O₃> Cr₂O₃ during both storms. Hematite (Fe₂O₃) which has high absorption potential in visible and near UV Wavelength is found to increase from 1.47 % (pre-DS) to 6.14 % (DS-1) and 5.43 % (DS-2), respectively. For the visible range spectrum (0.38–0.68 μm), it is discovered that the imaginary part of the refractive index (k) value rises from 0.004 to 0.048 during DS-1 and from 0.003 to 0.045 during DS-2. The present work could reduce the uncertainty in the radiation budget estimations of mineral dust over the Thar Desert region.