Phytoremediation of soils amended with landfill leachate sludge using Nicotiana alata L. under different heavy metal loads

Abstract

The application of sludge to infertile and organically deficient soils, combined with phytoremediation techniques to support soil restoration, shows promise for rehabilitating extensively disturbed sites, such as landfills. This study aimed to evaluate the effects of biosolid-amended soils with varying levels of heavy metal contamination on the phytoextraction efficiency, growth, and development of Nicotiana alata L. The sludge-amended soil was artificially contaminated with varying concentrations of Pb, Cr, and Ni. A Box-Behnken experimental design was employed with three factors, each representing a specific metal added at three levels: 0, 150 and 300 mg kg− 1 of dry mass. At harvest time, phenological and physiological parameters were measured in plant tissues. Heavy metal content, along with bioconcentration and translocation factors were determined to assess phytoextraction efficacy. The highest concentrations of Pb, Cr, and Ni observed in the roots were 269 mg kg⁻1, 273 mg kg⁻1, and 273 mg kg⁻1, respectively. However, in aerial tissues, the maximum values found were 38, 8, and 81 mg kg⁻1 for Pb, Cr, and Ni, respectively. Overall, N. alata exhibited a greater affinity for extracting and translocating Ni in its tissues, followed by Pb and, lastly, Cr. These differences may be associated with specific biological roles of Ni and variations in metal mobility in soils. Metal extraction variables were statistically linked to metal concentrations in the soil.Interaction effects among contaminants were observed, highlighting the importance of their joint assessment rather than one-dimensional analyses.