Non-destructive characterization of atmospheric particulate matter using SEM-EDS: Elemental mapping as a tool for...

The scanning electron microscopy (SEM) technique, coupled with energy dispersive X-ray spectrometry (EDS), is a key tool for characterizing particulate matter (PM), offering advantages such as in natura and non-destructive sample analysis. Published studies typically present SEM images alongside the elemental spectrum from EDS. Less commonly explored in the literature, the EDS elemental maps, performed with successive scans at appropriate resolution, can identify substances even when SEM analysis is compromised. In this present study performed PM analyses via SEM-EDS on samples collected using quartz and fiberglass filters during an environmental monitoring campaign across three regions of Rio de Janeiro, with no filter pre-treatment required. Blank filter characterization revealed that fiberglass filters contained Na, Ba, and Zn (~ 6%), while quartz filters is cleaner. The analysis enabled PM classification as organic/inorganic and natural/anthropogenic. Organic particles in the inland city included pollen and soot from biomass burning, while in the metropolitan area, clusters of small carbon spheres were linked to incomplete fuel combustion. Inorganic particles in the environmental reserve included aluminosilicates from crustal sources, while the inland city had iron-rich particles. Despite the long operation time, EDS elementary maps identified overlapping elements, enabling more accurate determination of PM's chemical composition.