Phytoremediation strategies present promising approaches for mitigating metal contamination in soils. This study examines the effectiveness of compost and biochar amendments, applied separately or in combination, in altering the properties of sandy mining waste soils (Sw) and affecting levels of metallic trace elements (MTEs). The research evaluates changes in soil physicochemical parameters, metal concentrations in soil pore water (SPW), and metal accumulation in Phaseolus vulgaris. Compost and biochar addition significantly affected SPW pH, which remained alkaline, while increasing SPW electrical conductivity (EC). A treatment combining 20% compost and 2% biochar (SwC20B2) enhanced soil enzymatic activities, with the highest values observed for FDA and ALP activities. Metal availability in the SPW appeared higher on D(0) compared to D(12), with notable reductions in Pb and Zn concentrations observed in the SwC20B2 treatment. Despite this decline, metal accumulation in plant shoots did not significantly differ from that in plants grown in unamended Sw, although all plants exhibited substantial growth. The minor decrease in SPW pH, likely due to compost, may have enhanced metal mobility at D(0). Notably, SPW Pb and Zn concentrations increased with higher compost rates, with SwC20B2 registering the highest Pb and Zn. Although these amendments did not directly alleviate metal mobility, they show potential for use in phytostabilization strategies by using suitable plant species.

The extensive use of copper (Cu) in viticulture has resulted in its high accumulation in soils, threatening ecosystems and soil health. Biochar, widely recognized for its potential in remediating metal-contaminated environments, offers promising sorption properties that strongly rely on both feedstock composition and the final biochar’s characteristics. This study investigates five biochars produced from different vineyard by-products; grape marc (BM), grape seed (BS), exhausted grape seed (BES), pruning (BP1), and pruning subjected to double pyrolysis (BP2). These biochars were comprehensively characterized in terms of physicochemical and structural properties, elemental composition, and potential toxicity. The maximum copper sorption capacities of the biochars ranged from Q _max of 39.35 to 134.36 mg Cu ² ⁺g ⁻¹ , depending on their properties, and followed the Langmuir isotherm and pseudo-second-order (PSO) kinetic models (for BM). Fourier-transform infrared spectroscopy (FT-IR) confirmed the presence of surface functional groups such as –OH, –COOH, and aromatic structures. Zeta potential (ZP) analysis indicated a predominantly negative surface charge across a wide pH range. Copper sorption was primarily attributed to π-cation interaction and precipitation mechanisms, while copper desorption assays revealed limited copper release, suggesting strong retention. Scanning electron microscopy (SEM), coupled with energy-dispersive X-ray spectroscopy (EDS), was used to analyze the morphology of the biochar and to verify copper incorporation in the Cu-loaded samples. Given the strong influence of feedstock on metal sorption efficiency, vineyard by-products were characterized by thermogravimetric analysis (TGA), FT-IR, and determination of lignocellulosic composition and physicochemical properties. Biochar from vineyard by-products, particularly grape marc (BM), demonstrated the highest potential, highlighting the valorization of vineyard by-products as a sustainable in situ remediation strategy in vineyard soils, in line with circular economy principles.

Mining activities often contaminate soils with heavy metals, generating environmental and health risks. This study investigates the ecotoxicity of muddy (Mw) and sandy (Sw) mining wastes on Phaseolus vulgaris and assesses the impact of five locally sourced biochar amendments on plant growth and soil pore water (SPW) properties. Most biochars improved water retention, except for argan nut shells (An) biochar, highlighting the importance of feedstock type. Sw supported better plant growth than Mw regardless of biochar addition, due to textural differences. Palm fronds (Pf) biochar significantly enhanced surface leaf area in Sw. SPW analysis revealed that biochar affected pH and electrical conductivity (EC) differently across soil types. Mw consistently increased pH, while Sw’s pH was biochar-dependent. A significant 5.1-fold EC increase was recorded in Sw amended with Pf. All biochars reduced Pb availability in Mw at planting, while Cu availability decreased in Sw at harvest. In Mw, Pb, Zn, and Cu, uptake and accumulation were unaffected by biochar, while a slight reduction was observed in Sw roots. A germination test with Lepidium sativum confirmed these findings, particularly the inhibition observed with An. This dual approach highlights the toxicity of mining soils and biochars’ potential as amendments for soil remediation programs.