Assisted phytoremediation of lead contaminated soil using Atriplex halimus and its effect on some soil physical properties

Lead is one of the most harmful trace elements found in soils. Despite reductions in environmental lead exposure, an historical lead pollution continues affecting soils in many areas. To mitigate the impact of lead, phytoremediation assisted with addition of chelating agents can be a suitable option. In order to evaluate the phytostabilization and/or phytoextraction capacity of Atriplex halimus, a pot assay with six phytoremediation treatments was established using different combination of two chelating agents (citric acid and fulvic acids), a composted substrate as organic amendment and a soil highly contaminated with lead (2952 ± 280 mg Pb kg−1, pH 6.30 ± 0.13) collected in the Valparaíso Region, Central Chile. Chelating agents were applied to irrigation water considering a concentration of 4 g L−1, while the organic amendment was applied at the beginning of the assay (dose of 5% v/v). After 180 days, the addition of the chelating agents significantly increased the Pb concentrations in tissues, an effect that was enhanced by application of the organic amendment, reaching concentrations of 32, 42, and 360 mg Pb kg−1 in leaves, stems, and roots, respectively. The treatments considered the addition of fulvic acids showed higher total plant dry weight levels (16.4 and 18.2 g, respectively) compared to the rest, which ranged from 8.3 to 10.0 g. With respect to soil physical properties, chelating agents increased microaggregate stability, but fulvic acids addition significantly decreased the soil available water. In general, Atriplex halimus demonstrated good potential for the phytostabilization of lead contaminated soils and a limited phytoextraction capacity.