Tridax procumbens L. como possível fitorremediadora para solos contaminados por cádmio e chumbo

Abstract

Contamination by heavy metals such as cadmium (Cd) and lead (Pb) represents a serious environmental issue due to their toxicity and the difficulty of restoring affected soils, with significant impacts on agriculture and human health. Phytoremediation has emerged as a promising alternative, using plants to mitigate soil toxicity. This study investigates the phytoremediation potential of Tridax procumbens L. in soils contaminated with Cd and Pb. Treatments consisted of different concentrations of Cd and Pb in the substrate (0, 1, 3, 5, and 7 mg kg⁻¹ – T0, T1, T3, T5, and T7, respectively), along with a control for each concentration. After the experiment, plants were harvested and separated into roots and aerial parts (stems and leaves). Following acid digestion of the samples, Cd and Pb quantification was performed by atomic absorption spectrometry with cold vapor atomization. Bioaccumulation factor (BAF), bioconcentration factor (BCF), and translocation factor (TF) were calculated to assess metal uptake and mobility. The results showed that Pb significantly reduced plant growth and impaired nutrient uptake, causing necrosis and chlorosis. Cd, on the other hand, had no significant impact. Biomass decreased progressively with increasing Pb concentrations, whereas Cd did not affect biomass production. Pb accumulated mainly in the roots, limiting its translocation to the aerial parts. In contrast, Cd was absorbed at concentrations from 3 mg kg⁻¹ and accumulated in both roots and shoots, showing regular translocation (TF = 1). Bioaccumulation factors for Cd were 2.25 at 5 mg kg⁻¹ and 1.61 at 7 mg kg⁻¹, indicating high uptake. The Tolerance Index (TI) was higher for Cd (82.25%) than for Pb (55.5%), classifying the plant as tolerant to Cd and moderately tolerant to Pb. The results indicate that Tridax procumbens has potential for the phytoremediation of Cd-contaminated soils, while its sensitivity to Pb limits its application for this metal. This study reinforces the relevance of phytoremediation in mitigating heavy metal contamination.