A study investigated the efficacy of nitrogen (NBC), phosphorus (PBC), sulfur (SBC), and iron (FBC)-modified biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More in remediating soils contaminated with cadmium (Cd) and lead (Pb). These biochars were prepared from maize straw using an impregnation-pyrolysis method and tested on calcareous soils in controlled pot experiments. The goal was to assess their capacity to immobilize heavy metals, enhance soil health, and reduce metal uptake in Chinese cabbage.

The findings revealed that biochar modifications significantly influence their remediation potential. PBC exhibited the highest adsorption capacity for Cd and Pb due to its rich phosphate functional groups, followed by SBC and NBC. FBC, despite its advanced pore structure, showed poor performance owing to its acidic nature, which lowered soil pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More and increased the availability of heavy metals.

PBC and SBC effectively immobilized Cd and Pb, transforming these metals into less bioavailable forms. Soil pH analysis showed PBC and SBC increased alkalinity, enhancing metal stabilization. Conversely, FBC reduced pH, leading to increased metal availability. Plant experiments demonstrated that PBC reduced Cd and Pb accumulation in Chinese cabbage by 34.4%-58.9% and 9.2%-53.1%, respectively, promoting healthier growth and reducing oxidative stress through enhanced antioxidant enzyme activity.

Among the treatments, PBC consistently outperformed others, improving soil conditions and minimizing heavy metal risks. NBC also proved effective, especially in reducing metal translocation in plants. While SBC offered moderate benefits, FBC was unsuitable for this purpose due to its acidity.

This study underscores the importance of tailoring biochar modifications for specific soil conditions and contaminants. PBC emerges as a promising amendment for mitigating heavy metal pollution in calcareous soils, supporting sustainable agriculture and environmental protection.

SOURCE: Bostani, et al (2025) Differentiated effects and mechanisms of N-, P-, S-, and Fe-modified biochar materials for remediating Cd- and Pb-contaminated calcareous soil. Ecotoxicology and Environmental Safety. https://doi.org/10.1016/j.ecoenv.2024.117661