Unveiling the potential of <i>Phaseolus vulgaris</i> L. for phytoremediation of As and Hg in agricultural environments in the vicinity of a mining area

This study assesses the phytoremediation potential of <i>Phaseolus vulgaris</i> L. for arsenic (As) and mercury (Hg) in agricultural areas near an abandoned mining site in Cerritos, San Luis Potosí (S.L.P.), México. In June 2023, 60 bean plant samples were collected from three communities (Derramaderos, Joya de Luna, and San José), spanning an area of 3.5 ha. As concentrations were determined by HG-GF AAS with duplicate digestions and instrumental replicates, and Hg by direct mercury analysis. Bioaccumulation (BAF) and translocation factors (TF), along with bioavailable soil fractions, were used to evaluate uptake and mobility. TF values ranged from 1.1 to 1.6 for As and 1.6 to 3.4 for Hg, with over 50% of both elements translocated to aerial tissues. The FAO/WHO does not establish limits for As or Hg in beans, so the results were compared with international guidelines. The levels of As (31.3 ± 1.9 μg kg⁻¹) and Hg (2.75 ± 0.16 μg kg⁻¹) in grains were below the maximum limits established by Chinese regulations (500 μg kg⁻¹ for As and 10 μg kg⁻¹ for Hg) and Brazilian standards for As in beans (100 μg kg⁻¹). These findings support the potential of phytoremediation but underscore the importance of long-term food safety monitoring. This study unveils a significant discovery regarding potentially toxic elements (As and Hg) in <i>Phaseolus vulgaris</i> L. plants growing near an abandoned mine historically used for cinnabar and arsenopyrite extraction, highlighting their potential for phytoremediation. Notably, for every sampled site and element evaluated, results consistently show a translocation factor greater than 1 for the aerial parts (stems, leaves, and grains), underscoring the plant’s exceptional capacity to transfer these elements. This characteristic, combined with the fact that phytoextraction is more environmentally friendly and cost-effective than the conventional method, emphasizes the promising potential of <i>Phaseolus vulgaris</i> L. for large-scale remediation efforts.