Phytoremediation Potential of Heavy Metals Using Biochar and Accumulator Plants: A Sustainable Approach Towards Cleaner Environments

Native plant species show significant promise for the remediation and rehabilitation of mine tailings contaminated with heavy metals (HM). Nonetheless, the harmful impact of HM can decrease plant survival, growth and reproduction, thereby diminishing the effectiveness of phytoremediation. Consequently, incorporating organic amendments into mine tailings, like biochar, can promote plant growth, decreasing the bioavailability of HM and their eventual potential to alter the food chain. This study aims to evaluate the capability of coconut fiber biochar in combination with <i>Sanvitalia procumbens</i> to phytostabilize HM in mine tailings by analyzing the effect of coconut fiber biochar on HM bioaccumulation levels (roots and leaves), as well as on morphological, physiological, and genotoxic parameters of <i>S. procumbens</i> grown in mine tailing substrate and mine tailing/biochar. Also, a physicochemical analysis of coconut fiber biochar was conducted. This research was conducted over 100 days on plants grown in greenhouse settings using two different substrates (mine tailing and agrolite [75/25 <i>v</i>/<i>v</i>] and mine tailing and coconut fiber biochar [75/25 <i>v</i>/<i>v</i>]). Every 25 days, 12 plants were selected per treatment for analysis. The bioaccumulation pattern exhibited by <i>S. procumbens</i> was Zn > Pb > Cu > Cd, in root and leaf tissues for both treatments. <i>S</i>. <i>procumbes</i> grown in mine tailing/biochar substrate showed the lowest HM bioaccumulation levels in both tissues in comparison to mine tailing substrate: Zn from 2.95 to 2.50 times lower; Pb 3.04 to 2.82; Cu 3.10 to 2.12; and Zn 2.12 to 3.00 in roots and leaves, respectively. The coconut fiber biochar was rich in functional groups, such as carboxyl and hydroxyl groups, which could favor HM adsorption. Immobilization percentage of HM by coconut fiber biochar showed the following pattern: Pb (66.33%) > Zn (64.50%) > Cu (62.82%) > Cd (55.39%). Incorporating coconut fiber biochar as an amendment improves HM phytostabilization efficiency by reducing their bioaccumulation, increasing biomass production and chlorophyll concentration, and reducing genetic damage levels. This strategy represents a sustainable approach towards reducing the ecological risk of HM biomagnification, alleviating the adverse effects of HM exposure on ecosystem health.