Contamination and Determinants of Potentially Toxic Elements in Road Dust Across Urban-Rural Gradient in Al-Qasim, Iraq

Road dust is a significant environmental concern in urban areas, acting as a reservoir for various potentially toxic elements (PTEs). This study investigates the spread and contamination of PTEs - As, Cd, Ni, Pb, Co, Cr, Cu, and V - in 50 road dust samples across an urban-rural (downtown, midtown, and rural areas) gradient in Al-Qasim City, Iraq. Fifty dust samples were collected, representing concentrations above world means for As (43.66 +/- 5.98 mg/kg), Ni (113.18 +/- 33.70 mg/kg), Cr (195.30 +/- 60.52 mg/kg), and Co (14.73 +/- 4.38 mg/kg). The differences between PTE concentrations were not significant across the urban-rural gradient. As showed a moderate level of geochemical contamination and, together with Cr and Ni, represented a significant enrichment. The pollution load index (PLI) was also extremely high (PLI >3) for all PTEs. Canonical Correspondence Analysis (CCA) indicated that Cr, Ni, and Co are closely associated with urban-related factors, including distance from the city center and road density. Cu, V, Pb, and Co also showed positive correlations with a Landsat-derived Normalized Difference Vegetation Index (NDVI), emphasizing the role of vegetation in PTE distribution. The findings revealed the complexity of PTE distribution due to the influence of various environmental factors, highlighting the urgent need for comprehensive environmental management and remediation strategies in the region.