Spatiotemporal Assessment of Soil and Vegetation Pollution with Toxic Metals from Road Traffic along the First Romanian Highway

The present study is dedicated to the assessment of soil and vegetation pollution with toxic metals on a section of the oldest highway in Romania, which has been in operation for more 50 years. In the assessment, the limits of the national legislation were complied with, and the analysis was related to locally identified reference levels at a distance from the road, the main potential source of pollution. The average concentrations of toxic metals in the investigated soils had wide amplitudes, and the variations were quite large. The recorded values of the concentrations were at high or moderate levels compared to those in previous research. The contamination factor, geo-accumulation index and other calculated indices indicate the presence of pollution at a moderate level. The concentrations of toxic metals in the range 0.15–0.42 mg/kg d.m. for Cd; 2.00–6.04 mg/kg d.m. for arsenic, 16.20–76.27 mg/kg d.m. for Cu, 17.40–28.40 mg/kg d.m. for Ni, and 149.00–535.00 mg/kg d.m. for Zn exceeded the reference levels in the soil in at least one studied area. The concentrations of Zn at two observation points exceeded the alert threshold, indicating the presence of pollution caused by road traffic. Among the factors that can influence pollution, the following can be distinguished: the specifics of the areas and the activities carried out, the increase in cars transiting the highway, and the location in relation to the entrance or exit areas of the highway.