• 中文核心期刊
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环境修复过程中溶解性有机质对镉环境行为影响研究进展

Research Progress on the Effect of Dissolved Organic Matter on the Environmental Behavior of Cadmium in the Environmental Remediation

  • 摘要: 随着经济社会的快速发展和镉(Cd)的持续排放,Cd污染日益成为中国乃至全球面临的重大环境问题。溶解性有机质(DOM)作为有机物中最活跃的组分,其分子量通常在几Da至几百kDa之间。DOM包含的羧基、羟基、酚基等多种活性官能团是环境中诸多重金属的配位体和迁移载体。DOM与Cd之间通过物理吸附、配体交换、表面络合等作用,显著影响着Cd在环境中的形态、生物可利用性、毒性和迁移转化。但从Cd污染修复的角度来看,Cd与DOM的络合作用是控制Cd修复成效的关键因素。DOM可以通过配体交换直接形成DOM-Cd二元络合物。根据DOM、Cd(Ⅱ)和矿物/金属表面阳离子(Mi/Me)的不同桥接位置,也可以形成A型或B型两种三元络合物。DOM来源多样,成分、结构复杂,不同条件下DOM对Cd呈现钝化或活化两种作用,在Cd污染原位钝化修复、淋滤修复或者植物修复中得到广泛应用。本文在总结近年来国内外相关研究基础上,对DOM和Cd的络合作用类型进行了重点评述,分析了DOM分子量、环境pH值、离子强度、温度等因素影响Cd-DOM络合作用及Cd吸附(解吸)机制,在此基础上探讨了DOM在土壤/沉积物Cd污染原位钝化修复、异位修复中的主要应用方向,这些方法有助于降低Cd污染修复环境风险和修复成本。通常情况下,小分子量DOM含有更丰富的官能团和更复杂的络合位点,容易形成可溶性DOM-Cd络合物,特别是对于分子量<30kDa的DOM 组分,可向环境中释放更多的Cd;在较高pH值环境条件下,则有利于增强DOM-Cd络合物的稳定性和土壤对Cd的吸附,而高离子强度对Cd吸附有很强的抑制作用;在Cd污染修复工作中,选择腐殖化程度较高的较大分子量DOM(>30kDa),并配施铁氧化物等无机钝化剂,可明显地提升Cd污染原位钝化修复成效;在Cd的化学淋滤或植物修复中,选择小分子量DOM(<5kDa)以提高污染修复的成效。未来该领域研究建议关注三方面:①不同分子量DOM与Cd的络合作用研究,精准解析DOM内部不同组分的功能基团与Cd的络合作用。②加强多种因素影响和控制下DOM对Cd吸附与解吸、迁移转化和生物有效性研究。③加强DOM在Cd污染修复技术研究,完善DOM与Cd相互作用的数值模拟模型,为Cd污染长期观测工作提供路径指引和数据支撑,更加精准地揭示Cd在环境中的迁移转化过程。

     

    Abstract: With the rapid development of the economy and society and the continuous emission of cadmium (Cd), Cd pollution has become a major environmental problem faced by China and even the world. As the most active component in organic matter, molecular weight of DOM is usually between several Da and several hundred kDa.The various active functional groups contained in DOM, such as carboxyl, hydroxyl, and phenolic groups, are ligands and migration carriers for many heavy metals in the environment. The interaction between DOM and Cd significantly affects the morphology, bioavailability, toxicity, and migration transformation of Cd in the environment through physical adsorption, ligand exchange, and surface complexation. However, from the perspective of cadmium pollution remediation, the complexation between Cd and DOM is a key factor controlling the effectiveness of Cd remediation. DOM can directly form DOM Cd binary complexes through ligand exchange. According to the different bridging positions of DOM, Cd(Ⅱ), and mineral/metal surface cations (Mi/Me), two types of ternary complexes can also be formed: A or B.DOM has complex and diverse sources, components, and structures, under different conditions, DOM exhibits two effects on Cd: passivation or activation, which has been widely used in in-situ passivation remediation, leaching remediation, or phytoremediation of Cd pollution. Based on the review of relevant research results in recent years, this article evaluates the types of complexation between Cd and DOM, and analyzes the effects of factors such as DOM molecular weight, pH, ion strength, and temperature on Cd-DOM complexation and the mechanism of Cd adsorption and desorption. On this basis, Summarize the application research of DOM in in-situ passivation remediation and ex-situ remediation of soil/sediment Cd pollution. These methods help to reduce environmental risks and remediation costs of Cd pollution remediation. Under normal circumstances, small molecular weight DOM contains richer functional groups and more complex coordination sites, making it easy to form soluble DOM-Cd complexes. Especially for DOM components with molecular weight<30kDa, which can release more Cd into the environment; Under higher pH environmental conditions, it is beneficial to enhance the stability of DOM-Cd complexes and soil adsorption of Cd, while high ionic strength has a strong inhibitory effect on Cd adsorption; In the remediation of Cd pollution, selecting larger molecular weight DOM (>30kDa) with higher humification degree and applying inorganic passivators such as iron oxides can significantly improve the in-situ passivation and remediation effect of Cd pollution; In the chemical leaching or phytoremediation of Cd, small molecular weight DOM (<5kDa) is selected to improve the effectiveness of pollution remediation. it is recommended to conduct research in the following three areas in the future: firstly, study the complexation between different molecular weights of DOM and Cd, and accurately analyze the complexation between functional groups of different components inside DOM and Cd. Secondly, strengthen the research on the adsorption, desorption, migration, transformation, and bioavailability of Cd by DOM under the influence and control of multiple factors. Finally, Strengthen the research on DOM in Cd pollution remediation technology, improve the numerical simulation model of the interaction between DOM and Cd, provide path guidance and data support for long-term observation of Cd pollution, and more accurately reveal the migration and transformation process of Cd in the environment.

     

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