Can rail transport-related contamination affect railway vegetation? A case study of a busy railway corridor in Poland

Rail transport is considered a serious risk to the environment; however, its environmental impact has been addressed insufficiently with many resulting uncertainties. A busy railway corridor was used to determine if the side of a railway track could distort the assessment of soil contamination with potentially toxic elements (PTEs) and if soil phytotoxicity changes up to 50 m away from the track. The studied soils showed a moderate to heavy level of contamination with Cu, Ni, Pb and Zn. Cu, Ni and Zn content decreased significantly with the distance from the track while Pb content increased slightly, probably because the Pb came predominantly from exhaust gases, while the source of the remaining elements was the abrasion of railway infrastructure components. The side of the railway track proved to be a significant factor that influenced Ni and Pb content in particular. The phytotoxicity test predominantly showed a slight inhibition of plant growth with a maximum value reaching 70.4% but with an absence of significant differences in phytotoxicity between the distances. The ecological risk assessment did not reveal a serious threat to the environment from the PTEs in the soil. Based on the results, it is appropriate to define a heavily polluted zone at a minimum distance of 50 m from the track, and both sides of the railway track should be assessed so that the actual level of contamination is not underestimated. Further research is needed on this issue urgently due to the severe and hitherto overlooked environmental risks associated with rail transport.