Phytoremediation by trees as a nature-based solution for mitigating metal contamination in urban soils

Trace metals in the environment are important pollutants affecting human health, particularly in urban areas worldwide. Phytoremediation as a nature-based solution (NBS) and environmentally friendly technology may decrease high concentrations of trace metals in urban soils, protecting public health (especially children) and contributing to urban sustainability. This study examined trace metal contamination of urban soils and trees in six cities in the Republic of Srpska (RS), Bosnia and Herzegovina (BiH) and investigated the potential of selected tree species for phytoremediation as a NBS for metal-polluted urban soils. Contamination of urban soils was assessed by quantifying the concentrations of 11 trace metals (B, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, and Zn). To estimate phytoremediation potential of urban tree species, concentration and bioconcentration factor of the 11 metals were quantified in leaves of three common and abundant tree species: Aesculus hippocastanum L. (horse chestnut), Platanus acerifolia Willd. (plane), and Tilia sp. (lime). The results showed that trace metal concentrations in leaf samples did not exceed toxicity threshold guideline values. Further assessments are needed to establish the true potential of the three species as NBS for urban soils.