Phosphorus-Loaded Biochar-Assisted Phytoremediation to Immobilize Cadmium, Chromium, and Lead in Soils

Soil contamination with heavy metals (HM) poses significant challenges to food security and public health, requiring the exploration of effective remediation strategies. This study aims to evaluate the remediation process of soils contaminated with Cd, Cr, and Pb using Lolium perenne assisted by four types of biochar: (i) activated coffee husk biochar (BAC), (ii) nonactivated biochar coffee husk (BSAC), (iii) activated sugar cane leaf biochar (BAA), and (iv) nonactivated biochar sugar cane leaf (BSAA). Biochar, loaded with phosphorus (P), was applied to soils contaminated with Cd, Cr, and Pb. L. perenne seedlings, averaging 2 cm in height, were planted. The bioavailability of P and heavy metals (HM) was monitored every 15 days until day 45, when the seedlings reached an average height of 25 cm. At day 45, plant harvesting was conducted and stems and roots were separated to determine metal concentrations in both plant parts and the soil. The study shows that the combined application of biochar and L. perenne positively influences the physicochemical properties of the soil, resulting in an elevation of pH and electrical conductivity (EC). The utilization of biochar contributes to an 11.6% enhancement in the retention of HM in plant organs. The achieved bioavailability of heavy metals in the soil was maintained at levels of less than 1 mg/kg. Notably, Pb exhibited a higher metal retention in plants, whereas Cd concentrations were comparatively lower. These findings indicate an increase in metal immobilization efficiencies when phytoremediation is assisted with P-loaded biochar. This comprehensive assessment highlights the potential of biochar-assisted phytoremediation as a promising approach for mitigating heavy metal contamination in soils.