Geochemistry of street dust in Tyumen, Russia: influence of traffic load

This study investigates the elemental composition, organic carbon content, pH values, and particle size characteristics in 50 road dust samples collected from Tyumen, a large city in Western Siberia (Russia). The content of 62 major and trace elements was studied using atomic emission spectrometry (ICP-AES) и inductively coupled plasma spectrometry (ICP-MS). It was revealed that the dust has an alkaline reaction pH = 7.4-10.2 and low organic carbon content (0.07-2.9%). The grain size distribution of the road dust samples revealed that the predominant grain size fraction was of 100-250 μm. The content of small particles (PM₂ and PM₁₀) representing the greatest environmental hazard is minimal on roads with an average traffic intensity. Studies have shown that the main road dust pollutants in Tyumen are Ni, Sb, Cr, Zn, and Co. The average geoaccumulation index (Igeo) values are ranked as Ni (2.2) > Sb (1.5) > Cr (1.3) > Zn (0.4) > Co (0.4) > Cu (0.2). The contamination evaluation through enrichment factor (EF) calculation showed that road dust is highly enriched in Ni and significantly in Cr and Sb. More than 80% of Zn, Co, and Cu and more than 90% of Ni, Sb, and Cr come from anthropogenic sources. The average concentration of Ni and Cr in the road dust of Tyumen is one order of magnitude higher than in other cities of the Earth where similar studies were carried out. The high Ni content is associated with the composition of local soils and roadways, increased content in vehicle exhaust gasses, and abrasion of metal parts. Calculations of the total enrichment index Ze showed that the level of road dust pollution in most of Tyumen's territory is hazardous.