Bioavailability of selected trace and rare earth elements to Juncus effusus L.: the potential role of de-icing chlorides in the roadside environment

Background and aim The presence of chlorides in soils, e.g., from de-icing salts may change metal availability to plants. Methods To assess the role of de-icing chlorides on bioavailability of metals, the samples of the rhizosphere soils, roots and shoots of Juncus effusus L. were collected monthly from April to June of 2019 in the vicinity of roads and analyzed for trace (Ag, Cd, Co, Cu, Pb, Zn) and rare earth elements (from La to Lu). Results Concentrations of Cl− were distinctly higher in the shoots than in the roots. Apart from Cd, the concentration sequence of the other metals was as follows: rhizosphere soils>roots>shoots. The bioaccumulation and translocation factors indicated that Cd was the most preferably transported to the shoots as opposed to Ag, Co, Pb and REEs that showed a very low translocation potential. Negative correlations, which were noted between Cu and Co in the shoots and Cl− in soils, revealed their role in salinity stress alleviation. All soil samples showed a positive anomaly of Ce and a negative anomaly of Eu, whereas the shoots showed in turn a negative anomaly of Ce and a distinct positive anomaly of Eu. The lowest salinity factors (K/Na, Ca/Na) of the shoots resulted from an increase of salinity in J. effusus by higher sodium concentrations derived from de-icing NaCl. Conclusions De-icing agents may change the uptake of other elements. In natural habitats, the factors affecting this process include: type of element, soil metal concentrations and interactions, and individual plant features.