Morphology and mineralogy of ambient particulate matter over mid-Brahmaputra Valley: application of SEM–EDX, XRD, and FTIR techniques

Abstract

AbstractAmbient particulate matter (PM), collected during a dust event over mid-Brahmaputra Valley of India, was characterized. The PM samples were analyzed using scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM–EDX), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) techniques. The SEM micrographs revealed varied shapes of the PM, viz. spherical, irregular, angular, cluster, flaky, rod-like, crystalline and agglomerate structures indicating the probable nature of their sources and formation as biogenic, geogenic, or anthropogenic. Some biogenic particles like plant materials, pollens, and diatoms were captured under SEM. The presence of diatom in PM samples was indicative of wind-blown dust from the dried bed of the Brahmaputra River. The honeycomb-like structures of brochosomes secreted by the leafhoppers of the Cicadellidae family were also captured. On the contrary, the background sample had mostly carbonaceous particles. The XRD and FTIR analyses indicated the presence of quartz, feldspar, kaolinite, illite, augite, and calcium aluminum silicate, cerussite, calcite, montmorllonite, and organic carbon. The airmass backward trajectory analysis explained the local contribution of the dust.