Recent research suggests that biochar amendment is a promising approach to mitigate soil contamination via immobilizing heavy metals and organic pollutants. Through intensive literature review, this paper was aimed to better understand the processes, mechanisms, and effectiveness of biochar in immobilizing chemical contaminants in soil. The quality characteristics of biochar as a soil amendment varied greatly with the feedstock materials and the pyrolysis conditions. Biochar products from different sources demonstrated remarkably diversified capacities and efficiencies for stabilizing soil contaminants. Soil-incorporated biochar was able to stabilize Cd, Cu, Ni, Pb, and Zn and reduce their bioavailability through enhanced sorption (based on electrostatic attraction, ion exchange, and surface complexation) and chemical precipitation (incurred from soil pH elevation and ash addition of carbonates and phosphates). The stabilization efficacy was largely determined by cation exchange capacity, pH, and ash content of the biochar. Biochar amendment increased the mobility of anionic toxic elements [e.g., CrO42-, AsO3-, and Sb(OH)6-] in soil. Soil-incorporated biochar was also able to adsorb non-polar organic compounds (through pore filling, partition, and hydrophobic effect) and polar organic compounds (via H-bonding, electrostatic attraction, specific interaction, and surface precipitation). The adsorption efficiency was controlled by the biochar surface properties specific surface area, microporosity, and hydrophobicity. Biochar may facilitate the mineralization of organic pollutants by enhancing soil microbial activities. The effectiveness of biochar-facilitated soil remediation was case specific, changing with the biochar source, amendment rate, placement, soil type, and pollutant species. More field studies are needed to evaluate the long-term effectiveness of biochar-facilitated soil remediation under practical circumstances.

中文翻译：

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生物炭促进土壤修复：机制和功效变化

最近的研究表明，生物炭改良剂是一种通过固定重金属和有机污染物来减轻土壤污染的有前途的方法。通过深入的文献综述，本文旨在更好地了解生物炭在土壤中固定化学污染物的过程、机制和有效性。生物炭作为土壤改良剂的质量特性因原料和热解条件而异。来自不同来源的生物炭产品在稳定土壤污染物方面表现出显着多样化的能力和效率。掺入土壤的生物炭能够稳定 Cd、Cu、Ni、Pb 和 Zn，并通过增强吸附（基于静电吸引、离子交换、和表面络合）和化学沉淀（由土壤 pH 值升高和碳酸盐和磷酸盐的灰分添加引起）。稳定效果很大程度上取决于生物炭的阳离子交换容量、pH 值和灰分含量。生物炭改良剂增加了土壤中阴离子有毒元素 [例如 CrO42-、AsO3- 和 Sb(OH)6-] 的迁移率。掺入土壤的生物炭还能够吸附非极性有机化合物（通过孔隙填充、分配和疏水作用）和极性有机化合物（通过氢键、静电引力、特定相互作用和表面沉淀）。吸附效率受生物炭表面性质、比表面积、微孔率和疏水性控制。生物炭可以通过增强土壤微生物活动促进有机污染物的矿化。生物炭促进土壤修复的有效性因具体情况而异，随生物炭来源、修正率、放置、土壤类型和污染物种类而变化。需要更多的实地研究来评估在实际情况下生物炭促进土壤修复的长期有效性。