Selected Properties and Composition of Saharan Dust in Relation to Atmospheric Deposition in the Košice Area (Slovakia)

Abstract

This paper analyses Saharan dust (SD) from settled precipitation from the episode of its record occurrence in eastern Slovakia at the end of March and early April 2024.The aim is to assess the impact of SD on atmospheric deposition (AD) and particulate matter immissions in the Košice area with the metallurgical industry present. The particles' size and distribution, chemical, and phase composition were analyzed. The methods of laser granulometry, electron microscopy (SEM and EDX), ICP MS, CHNS, and X - ray powder diffraction analysis were used. Saharan dust is polydisperse, with a mean geometric grain diameter of 15.1 μm; the proportion of particles with sizes below 10 and 2.5 μm is 37 and 10.9 %, respectively. The proportion of particles larger than 20 μm is 45 %. The SD sample is polymineralic, with quartz as the dominant component, accompanied by calcite and dolomite to a lesser extent. Additionally, feldspars, micas, kaolinite, and other common phyllosilicates and rock - forming minerals were confirmed. The main components of the analyzed EDX spectra, apart from oxygen and silicon, also included elements such as Al, Ca, K, Fe, Mg, and Na. The SD sample contained a relatively high carbon content (9.6%). Based on their occurrence in the spectra, the elements were present in the following order: O, Si, Al, Fe, Ca, Mg, K, C, Ti, Na, Cu, P, Mn, Nb, Ba, Br, Cr, and Pt. The chemical composition of SD is very similar to the average composition of the Earth's crust. Compared to the concentrations of the monitored elements in AD, the SD sample exhibited higher levels of aluminum and, to some extent, calcium and magnesium. In the case of other elements, their concentrations in AD from an area in the metallurgical industry were significantly higher than in Saharan dust. The estimated contribution of Saharan dust to the atmospheric deposition of the solid fraction in the study area ranges from 4.6% to 22%, depending on the emission loading rate.