Assessing PTEs in a polluted urban green environment and proposing sustainable approaches for its recovery

This study investigates the potential of common plant species to uptake contaminants from a polluted urban soil, which has remained abandoned for three years due to toxicity concerns, with the goal of enabling its multifunctional reuse as an urban green space. We firstly conducted a taxonomic survey of the spontaneously growing vegetation, from which we selected the most suitable species for further study. Plant ability to concentrate potentially toxic elements (PTEs) and essential nutrients was assessed by a semi-quantitative ICP-OES assay and, based on this preliminary screening, five plant species were chosen for a controlled in field experiment. Before the trial, pollutant concentrations were evaluated in the irrigation water (drawn from the local aquifer) and the soil. Furthermore, the mobility of six key pollutants exceeding regulatory limits (Co, Cr, Cu, Ni, Pb, Zn) was assessed with the BCR protocol and pollutants were found to be non-mobile (< 7 %), with Zn only exception.

The five-month in field experiment was conducted during the dry season and involved planting the selected species under different soil conditions. Two soil amendments were applied: a pH-lowering agent (FeSO₄) to enhance PTEs mobility and uptake, and an organic compost to promote biomass production thus increasing the total element recovery. Untreated control plots were also included for comparison.

Soil improvers affected both plant uptake patterns and biomass production. While all species accumulated nutrients and low to moderate levels of PTEs (bioaccumulation and translocation factors were below 1 for all pollutants), they developed substantial biomass, especially in compost-amended sections. At the end of the growing season, the harvested biomass was successfully processed to recover its cellulosic fraction, achieving optimal yields (∼45 %) while minimizing residual waste.