Diagnosing the traffic impact on roadside soils through a multianalytical data analysis of the concentration profiles of traffic-related elements

•Traffic-related elements accumulate in upper soil close to the road.•Concentration of some metals is above the target values according to the local legislation.•There is a high concentration gradient of Traffic-Related Elements in old roads with high traffic density.•The Igeo helps in establishing traffic impacted areas.•PCA analysis of soil transects reveals some of the traffic metals with a decreasing profile with depth.

The road traffic has become one of the most serious environmental problems in many cities and the main source of pollution of urban soils. To diagnose properly the magnitude of such impacts on roadside soils, eight urban and metropolitan soils were selected as a function of traffic density, distance to the road and years of operation, for which the concentration of 60 elements (major, minor and trace elements) were measured by semi-quantitative ICP-MS after acid digestion, as a first step in assessing the traffic impact. With this information, a comprehensive study was carried out focusing on the quantitative analysis of the concentration of 46 elements from the 8 sampling areas, analyzing the vertical and horizontal distributions of the metals in the roadside soils. The chemometric analysis showed that only the traffic-related elements accumulate in topsoil and present a high decreasing profile with depth and the distance to the road; however, this clear behavior takes places only in old roads that have undergone the traffic impact for a long time, but not in new roads or roads with low traffic density. Finally, the geoaccumulation indexes are suggested to be used instead of the local guidelines to assess the pollution state of the roadside soils, especially for the emerging trace elements like Antimony.