Physicochemical and morphological characterization of atmospheric coarse particles by SEM/EDS in new urban central districts of a megacity

Physicochemical and morphological characteristics of atmospheric particles in new urban centers of fast-developing megacities are not well understood. In this study, atmospheric coarse particles (PM₂.₅–₁₀) were simultaneously collected in multiple stations (10) in new urban centers, namely Beylikduzu, Buyukcekmece, and Esenyurt, of Istanbul using a modified passive particulate sampling method. Scanning electron microscope and energy dispersive X-photon spectroscopy (SEM-EDS) was used to investigate the size distribution characteristics, chemical composition and their weight percent abundances, and morphological properties of the collected particles. The particle clusters were mainly dominated by Ca-rich Al silicates, Ca dominant, Ca- and S-rich, and NaCl particles, respectively. Their potential sources were assigned to the natural sources (e.g., wind erosion, soil resuspension, and sea sprays) and anthropogenic activities (construction, transportation, mining and crushing, and cement production). In addition to the major contributions (up to 47% of particle number abundance), the minor contribution clusters (less than 1%) with transitional metals rich particles (Fe, Zn, and Cu rich) mainly from anthropogenic sources (combustion, traffic, and vehicular emissions) were identified. The typical size range (> 0.65 to < 11.00 μm) distribution of the major particle clusters fits a left-skewed modal distribution with a peak at 1.10–2.30-μm size range. However, the number of particles decreases significantly with increasing distance to the source, and this justification is stronger for larger size fractions (> 2.3 μm). Particle numbers and varieties indicated significant spatial variations depending upon the identified sources, meteorological factors, and temporal conditions. In general, the results of this study suggest that the passive sampling of PM₂.₅–₁₀ coupled with SEM/EDS based single-particle analysis is an effective tool to understand the physicochemical characterization and spatial and temporal variations of atmospheric particles in urban environments.