Wu Gang, Islam Md Shoffikul, Fu Qingling, Liu Yonghong, Zhu Jun, Fang Linchuan, Hu Hongqing
State Environmental Protection Key Laboratory of Soil Health and Green Remediation, Hubei Key Laboratory of Soil Environment and Pollution Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
State Environmental Protection Key Laboratory of Soil Health and Green Remediation, Hubei Key Laboratory of Soil Environment and Pollution Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China; Department of Soil Science, University of Chittagong, Chattogram 4331, Bangladesh.
J Environ Sci (China). 2025 Dec;158:324-336. doi: 10.1016/j.jes.2025.03.005. Epub 2025 Mar 8.
Cadmium (Cd) contamination in agricultural soils poses severe threats to human health and ecosystem integrity. While biochar is recognized for its ability to immobilize heavy metals, the impact of plant-derived low molecular weight organic acids (LMWOAs), such as citric acid (CA), on this process remains unclear. This study shows that CA and biochar synergistically immobilize Cd in alkaline soil from extensively polluted southeastern Hubei, China. Soils were amended with maize stover biochar at rates of 0, 0.5 %, 1 %, and 2 % (W/W), with or without CA addition (1 mmol/L), and incubated for 80 days. Results show that biochar significantly reduced bioavailable Cd, with a 2 % application decreasing extractable Cd by 26.84 %. Unexpectedly, CA alone increased Cd mobility by 9.38 %; however, when combined with high-dose biochar, CA and biochar synergistically enhanced Cd immobilization, reducing bioavailable Cd by 27.40 %. Advanced analytical techniques, including BCR sequential extraction, X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy with energy-dispersive X-ray spectroscopy, confirmed that the interaction between biochar and CA altered Cd speciation, promoting its stabilization. This study is the first to show that CA and biochar synergistically immobilize Cd in alkaline soils, disproving the idea that LMWOAs hinder biochar's metal remediation. Our findings show that biochar can prevent or even harness LMWOAs' activating effects on Cd, indicating its great potential for sustainable Cd remediation in alkaline soils. This study improves our understanding of biochar-soil interactions in organic acids and gives new scientific bases for enhancing heavy metal-contaminated soil remediation procedures.
农业土壤中的镉（Cd）污染对人类健康和生态系统完整性构成严重威胁。虽然生物炭因其固定重金属的能力而受到认可，但植物源低分子量有机酸（LMWOAs），如柠檬酸（CA），对这一过程的影响仍不清楚。本研究表明，CA和生物炭在来自中国湖北东南部重度污染的碱性土壤中对Cd具有协同固定作用。以0%、0.5%、1%和2%（W/W）的比例用玉米秸秆生物炭改良土壤，添加或不添加CA（1 mmol/L），并培养80天。结果表明，生物炭显著降低了生物可利用态Cd，施加2%的生物炭可使可提取Cd降低26.84%。出乎意料的是，单独的CA使Cd的迁移率提高了9.38%；然而，当与高剂量生物炭结合时，CA和生物炭协同增强了Cd的固定作用，使生物可利用态Cd降低了27.40%。包括BCR连续提取、X射线衍射、傅里叶变换红外光谱和带有能量色散X射线光谱的扫描电子显微镜在内的先进分析技术证实，生物炭与CA之间的相互作用改变了Cd的形态，促进了其稳定化。本研究首次表明，CA和生物炭在碱性土壤中对Cd具有协同固定作用，反驳了LMWOAs会阻碍生物炭对金属修复的观点。我们的研究结果表明，生物炭可以预防甚至利用LMWOAs对Cd的活化作用，表明其在碱性土壤中可持续修复Cd方面具有巨大潜力。本研究增进了我们对生物炭与土壤在有机酸中相互作用的理解，并为加强重金属污染土壤修复程序提供了新的科学依据。
