Tridax procumbens: Applicable Weed in Phytoremediation and Bioindication of Soil Contamination by Mercury

Spontaneous plants have significant potential for phytoremediation of metal-contaminated soils. This study evaluated Tridax procumbens L. for mercury (Hg) decontamination. The plant was cultivated in a sand and vermiculite (1:1) substrate with Hg concentrations of 0, 1, 3, 5, and 7 mg kg^-1. After 90 days, biometric growth and total Hg uptake by the aerial and root tissues were analyzed. Bioconcentration (BCF), translocation (TF), and bioaccumulation (BAF) factors, along with the elongation ratio (RER), tolerance (TI), and absorption (AI) indices, were used to assess the phytoremediation potential. BAF ranged from 1.46 to 11.04, BCF ranged from 6.07 to 30.31, and TF averaged 0.72, showing high Hg accumulation in roots and shoots. Vegetative development was affected by the concentration of Hg in the substrate (Hg_s), with TI varying from 97 to 6.62% at Hg_s of 1 and 7 mg kg^-1, respectively. AI increased proportionally to Hg_s, ranging from 8.12 to 17.81 μg, indicating that the mass of Hg absorbed by the plant increased even with a reduction in biomass production. T. procumbens, despite the reduction in its biomass, did not show any visual signs of chlorosis or necrosis, demonstrating resistance to Hg toxicity. These findings suggest that T. procumbens is a promising phytoremediator for soil decontamination and bioindication of Hg contamination, contributing to global efforts to protect, restore, and promote the sustainable use of terrestrial ecosystems and to halt and reverse land degradation and biodiversity loss.