The origin of toxic elements, environmental risk and new methods on prediction of weathering processes: case study of roadside soils (highway E75, Vojvodina, Serbia)

This composite study presents detailed instructions on the applicability of the results of a sequential extraction method (SE), coupled with statistical analyses, a Secondary Phase Enrichment Factor (Kspef), risk assessment indices, and, for the first time, the Chemical Index of Alteration (CIA). The study gives important data on the current risk of mobility of the elements and the methodology of appropriate measures before establishing an effective mitigation strategy and predicting the risk of mobility after changing environmental conditions, such as the harmful effects of ongoing climate change. The combination of techniques is used to assess the origin and contamination level of potentially toxic elements in the roadside agricultural soil impacted by traffic at Highway E75 (Serbia). The results show that B, Ni, Co, V, Ba, Cr, As, and Mo at most localities are of natural origin, sourced by a protracted decomposition of the geological matrix. Cu, Zn, Pb, Hg, Sb, and Cd have natural and anthropogenic origins (traffic and agricultural activities). Ba has the highest bio/geoavailability and belongs to the group of elements with a higher environmental risk. Groups with a moderate environmental risk include the elements As, Cd, Co, Ni, and V. A moderate to high-risk level of contamination of the soils with Pb, Cu, Zn, Sb, and Hg is documented exclusively at particular localities. The results of SE, coupled with the CIA coefficient, are applicable to predict the processes of chemical alteration of the mineral components of soils, including evaluating a degree of natural soil contamination.