Biochar has attracted interest due to its ability to improve soil fertility, soil carbon, and crop yield. Also, biochar can adsorb metals and render them less bioavailable. We investigated the soil availability, sequential extraction, and maize uptake of Cd, Pb, and Zn in a highly contaminated soil amended with rice straw biochar rates (0.0, 5.0, 10.0, 20.0, and 30.0 Mg ha⁻¹). We hypothesized that biochar application to the soil cultivated with maize attenuates metal toxicity and mobility in slag-polluted soils near an abandoned Pb smelting plant in Brazil. Results showed that applying biochar increased the soil organic carbon, CEC, and P up to 27, 30, and 107, respectively. Plant accumulation of P and N was 104 and 32% higher than control, while aerial and root biomasses were increased by 18 and 23%. The sequential extraction showed that Pb and Zn in the original soil were retained mainly in residual fractions (94 and 87%, respectively), while Cd was mostly allocated in the organic fraction (47%). Biochar rates increased the proportion of Cd in the organic fraction to 85%, while Pb and Zn were redistributed mainly into iron oxides. The Cd, Pb, and Zn bioavailability assessed by DTPA decreased 32% in the biochar-amended soil, reducing plants’ metal uptake. The maize biomass increase, metal soil bioavailability decrease, and low metal concentration in shoots driven by biochar indicate that phytoattenuation using rice straw biochar and maize cultivation could reduce risks to humans and the environment in the polluted sites of Santo Amaro.

生物炭因其提高土壤肥力、土壤碳和作物产量的能力而引起了人们的兴趣。此外，生物炭可以吸附金属并降低它们的生物利用度。我们调查了用稻草生物炭速率（0.0、5.0、10.0、20.0 和 30.0 Mg ha ^-1）。我们假设在巴西一个废弃的铅冶炼厂附近，将生物炭应用于种植玉米的土壤会减弱金属毒性和金属毒性和流动性。结果表明，施用生物炭可使土壤有机碳、CEC和P分别提高至27、30和107。P 和 N 的植物积累分别比对照高 104% 和 32%，而地上和根系生物量分别增加了 18% 和 23%。顺序提取表明，原始土壤中的铅和锌主要保留在残留部分（分别为 94% 和 87%），而 Cd 主要分配在有机部分（47%）中。生物炭率使有机部分中 Cd 的比例增加到 85%，而 Pb 和 Zn 主要重新分配到氧化铁中。镉、铅、DTPA 评估的 Zn 生物有效性在生物炭改良土壤中降低了 32%，从而降低了植物对金属的吸收。玉米生物量增加、金属土壤生物有效性降低以及由生物炭驱动的枝条中金属浓度降低表明，使用稻草生物炭和玉米种植进行植物减毒可以降低圣阿马罗污染场地对人类和环境的风险。