Atmospheric particulate matter (PM), particularly nuisance dust in arid regions, poses significant environmental and health risks due to its complex composition and ability to transport toxic elements. This study investigates the soluble, insoluble, and total concentrations of key elements including sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), and manganese (Mn) in fine dust particles collected from Samarra city, Central Iraq, a semi-arid urban area prone to frequent dust storms. Sampling was conducted weekly from early June to late November at three monitoring stations using a standardized sedimentometer method (ASTM, 1982). Soluble fractions of Na, K, Ca, and Mg were analyzed via flame photometry, while insoluble and total fractions of Fe and Mn, along with other elements, were determined using atomic absorption spectrometry (AAS) following appropriate digestion procedures. Results revealed pronounced seasonal trends, with peaks in soluble, insoluble, and total concentrations during mid-summer (July–August), driven by high temperatures, low precipitation, and shamal winds mobilizing crustal materials from local soils and distant desert sources. Calcium dominated total concentrations (up to ~422 mg/g), reflecting the region's carbonate-rich sedimentary geology (limestone and dolomite), followed by Mg (up to ~68 mg/g), Fe (up to ~82 mg/g), Na (up to ~44.5 mg/g), K (up to ~25.7 mg/g), and Mn (up to ~4.35 mg/g). Soluble fractions were particularly high for Na and Ca, while insoluble phases dominated for Fe, Mn, and Mg. Atmospheric sedimentation rates varied markedly, peaking at ~6 g/m²/week in late July (highest at Station 1), with secondary peaks in mid-June (~5.5 g/m²/week) and an overall range of ~1.3–5 g/m²/week, declining in late summer before autumn increases. Igeo values indicated moderate to strong contamination for Ca (3.0–3.60), moderate contamination for Na (~0.78–1.6), Mg (~1.10–1.45), and Mn (~1.08–1.72), no contamination for K (~–0.8 to –1.3), and negligible contamination for Fe (~–0.35 to 0.2). Atmospheric sedimentation rates in Central Iraq city dust varied from 1.3 to 6 g/m²/week, peaking at ~6 g/m²/week in late July (highest at Station 1) during intense shamal-driven dust storms. These patterns underscore predominantly natural crustal origins with minor anthropogenic influences from urban resuspension, traffic, and localized activities. The findings highlight the critical role of regional dust cycles, Tigris valley salinization, and carbonate geology in PM dynamics in central Iraq. Elevated Ca enrichment and high summer deposition rates pose risks for respiratory health, soil alkalinization, and ecosystem nutrient cycling.
