Traffic-Related Pollutants in Roadside Soils of Different Countries in Europe and Asia

We investigated the magnetic and chemical properties of the roadside soil samples collected from five European and Asian countries. Spots in which cars slowed down and/or accelerated due to the traffic organization (speed limits, junctions, and traffic lights) were selected for sampling. Apart from the Zabrze site (Poland), the magnetic susceptibility and heavy metal contents decreased with increasing distance from the road edge. The highest mass-specific magnetic susceptibility values (chi) were observed in the samples collected from Mumbai (India) and Zabrze (Poland). Moreover, the high contents of Fe, Ni, Mn, and Co were observed in Mumbai, whereas in Zabrze, all the examined elements demonstrated high contents, except for Co. Analyses revealed that magnetite was the main magnetic mineral in the roadside soil samples. The high correlation coefficients (r=0.87) between the magnetic susceptibility values and the total Fe content demonstrated that Fe occurred mainly as ferrimagnetic particles of technogenic origin resulting from traffic emissions. The traffic origin of the pollutants was also confirmed by the increased contents of the typically anthropogenic metals (Pb, Zn, Cd, and Cu) and a good correlation (r=0.83) between the Ti and Mo contents, which do not occur in natural associations. The ratio between particular polycyclic aromatic hydrocarbons (PAHs) and high content of PAHs typical for car exhaust also implied traffic as their main source.