Effects of citric acid on Cd speciation in biochar-amended contaminated soils.

IF 3.2 3区环境科学与生态学 Q3 ENGINEERING, ENVIRONMENTAL

Environmental Geochemistry and Health Pub Date : 2025-06-21 DOI:10.1007/s10653-025-02596-5

Bingyao Xu, Jiayu Xu, Meiqi Wang, Weifeng Chen, Usman Farooq, Renhui Miao, Zhichong Qi

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引用次数: 0

Abstract

Understanding the roles of low-molecular-weight organic acids (LMWOAs) in the transformation of chemical speciation of heavy metals in contaminated soil amended by biochar is of great significance for assessing the effectiveness of this carbonaceous amendment. The impacts of citric acid (a typical LMWOA) on the redistribution of Cd in contaminated soil amended by different amounts of biochar (1-5%) generated at various pyrolysis temperatures (300 ~ 700 °C) were investigated in this study. Biochar treatments reduced the exchangeable fraction (F1) of Cd after one year of incubation. Meanwhile, biochars produced at lower temperatures with more surface functional groups showed better immobilization performances (e.g., the F1 values decreased from 54.5% (CK) to 31.7% (adding 5% biochar generated at 300 °C) and 37.3% (adding 5% biochar generated at 700 °C), respectively). In comparison, the iron and manganese-bound fraction (F3) and organic bound fraction (F4) of Cd exhibited increased trends because of the increase in Cd linked to organic compounds and mineral oxides of soil particles. The residual fraction (F5) also showed an increased trend within a long remediation action. That is, the application of biochars favored the Cd redistribution into more stable speciations and led to a decrease in mobility. However, the addition of citric acid was beneficial in transforming immobilized fractions of Cd into mobilized fractions due to the H⁺-driven dissolution and release of Cd precipitation (e.g., for the soil treated with 3% biochar generated at 300 °C, the F1 values increased from 35.9% (before adding citric acid) to 43.5% (after adding citric acid)). Moreover, the high ratio of biochar addition could buffer soil pH reduction caused by adding citric acid and inhibit the dissolution of Cd. The findings have implications for assessing the effectiveness of biochar used as an amendment for reducing the risk of Cd in the rhizosphere of contaminated soils.

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柠檬酸对生物炭改性污染土壤中Cd形态的影响

了解低分子量有机酸（LMWOAs）在生物炭改性污染土壤中重金属化学形态转化中的作用，对评价这种碳质改性的有效性具有重要意义。本研究考察了柠檬酸（一种典型的LMWOA）对不同热解温度（300 ~ 700℃）下不同生物炭（1-5%）改性的污染土壤中Cd再分布的影响。经过一年的培养，生物炭处理降低了Cd的交换分数（F1）。同时，表面官能团较多、温度较低的生物炭具有较好的固定化性能(F1值分别从54.5% （CK）降至31.7%（添加5% 300℃生成的生物炭）和37.3%（添加5% 700℃生成的生物炭）。Cd的铁锰结合分数（F3）和有机结合分数（F4）表现出增加的趋势，这是由于Cd与土壤颗粒的有机化合物和矿物氧化物结合的增加。在长时间的修复过程中，残留分数（F5）也呈现出增加的趋势。也就是说，生物炭的应用有利于镉重新分配到更稳定的物种，并导致流动性降低。然而，由于H+驱动Cd沉淀的溶解和释放，柠檬酸的加入有利于将固定的Cd转化为移动的Cd组分（例如，在300℃下生成3%的生物炭处理土壤，F1值从添加柠檬酸前的35.9%增加到添加柠檬酸后的43.5%）。此外，高添加比例的生物炭可以缓冲柠檬酸引起的土壤pH降低，并抑制Cd的溶解。该研究结果对评估生物炭作为一种改良剂降低污染土壤根际Cd风险的有效性具有重要意义。

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来源期刊

Environmental Geochemistry and Health 环境科学-工程：环境

CiteScore

8.00

自引率

4.80%

发文量

279

审稿时长

4.2 months

期刊介绍： Environmental Geochemistry and Health publishes original research papers and review papers across the broad field of environmental geochemistry. Environmental geochemistry and health establishes and explains links between the natural or disturbed chemical composition of the earth’s surface and the health of plants, animals and people. Beneficial elements regulate or promote enzymatic and hormonal activity whereas other elements may be toxic. Bedrock geochemistry controls the composition of soil and hence that of water and vegetation. Environmental issues, such as pollution, arising from the extraction and use of mineral resources, are discussed. The effects of contaminants introduced into the earth’s geochemical systems are examined. Geochemical surveys of soil, water and plants show how major and trace elements are distributed geographically. Associated epidemiological studies reveal the possibility of causal links between the natural or disturbed geochemical environment and disease. Experimental research illuminates the nature or consequences of natural or disturbed geochemical processes. The journal particularly welcomes novel research linking environmental geochemistry and health issues on such topics as: heavy metals (including mercury), persistent organic pollutants (POPs), and mixed chemicals emitted through human activities, such as uncontrolled recycling of electronic-waste; waste recycling; surface-atmospheric interaction processes (natural and anthropogenic emissions, vertical transport, deposition, and physical-chemical interaction) of gases and aerosols; phytoremediation/restoration of contaminated sites; food contamination and safety; environmental effects of medicines; effects and toxicity of mixed pollutants; speciation of heavy metals/metalloids; effects of mining; disturbed geochemistry from human behavior, natural or man-made hazards; particle and nanoparticle toxicology; risk and the vulnerability of populations, etc.