The Impact of Proximity to Road Traffic on Heavy Metal Accumulation and Enzyme Activity in Urban Soils and Dandelion

Urban soils usually comprise a mosaic of various types and usually present with elevated contents of heavy metals. This is due to their long-term accumulation in the soil, which is ensured by the continuous emission of pollutants, including from road traffic. The aim of this study was to estimate the impact of traffic pollution on the state of the soil environment using a phytoindicator (Teraxacum officinale). The contents of selected heavy metals in the soil and dandelion organs and the activities of selected redox enzymes in the soil in the vicinity of a busy city road were determined. The degree and direction of the movement of heavy metal ions in plants were assessed using the translocation factor (TF) and bioaccumulation factor (BCF). Selected indicators (AF-absorption factor, CF-contamination factor, EF-enrichment factor, PN-Nemerow's pollution index, PLI-pollutant load index) were used to determine possible heavy metal contamination in soils, and the adaptation mechanisms of dandelion were evaluated by assessing selected enzymatic and non-enzymatic antioxidising systems. The research results confirmed that the proximity of a busy street reduced the enzymatic activity of the soil and increased the content of heavy metals in the soil and in dandelion. The heavy metal content levels did not exceed the permissible standards for soils in communication areas. The indicators used did not provide a clear answer as to the degree of anthropogenic contamination with individual metals. The higher contents of the metals in question in the above-ground parts of plants suggest that they may be caused by the impact of atmospheric pollution and not by the metal contents in the soil.