溶解性有机质-针铁矿-铅复合体系中铅的界面互作分子机制研究

Dissolved organic matter (DOM) is the most active component of soil organic matter and can interact extensively with soil minerals and heavy metals. The study of micro-interface interaction mechanism in DOM-mineral-heavy metal system is important in predicting the evaluation of the migration, transformation, and bioavailability of heavy metals. However, the key factors and their molecular mechanisms affecting the adsorption of heavy metals in the mineral-organic matter composite system are still unclear. The applicant and his team have been engaged in interfacial adsorption studies of soil minerals, organic matter and heavy metals for a long time. This project selects goethite as a model mineral and extracted dissolved organic matter from different sources to study the influence of DOM and its different fractions on the adsorption of lead by goethite. The interface adsorption experiments and chemical morphological models are used to acquire the adsorption capacity, affinity, element content, molecular weight distribution, affinity/hydrophobicity, surface charge density, site concentration, functional groups, thermodynamic properties, etc., and quantitatively describe the species and distribution of lead. This study may facilitate the advances in the research field of DOM on the adsorption of lead from the molecular scale, and reveal quantitative morphological distribution and interfacial binding mechanism of lead in goethite/DOM/lead composite system.

溶解性有机质(Dissolved organic matter，DOM)是土壤有机质中最具有活性的组分之一，可与土壤矿物、重金属发生广泛的相互作用，研究DOM-矿物-重金属的微界面互作机制，对于预测评估重金属的迁移转化、生物有效性具有重要意义。但DOM影响矿物吸附重金属的关键因素及其分子机制还不明确。申请人及其团队一直从事土壤矿物、有机质和重金属的界面吸附研究。本课题选取针铁矿作为模式矿物，提取不同来源的溶解性有机质，研究DOM及其不同组分对针铁矿吸附铅的影响，将界面吸附实验与化学形态模型相结合，借助多种现代分析技术获取吸附量、亲和力、元素含量、分子量分布、亲/疏水性、表面电荷密度、位点浓度、官能团、热力学特性等性质，从分子尺度探讨DOM对针铁矿吸附铅的影响，揭示铅在针铁矿/DOM/铅复合体系中定量形态分布和界面结合机制。

溶解性有机质（Dissolved organic matter，DOM）是生态系统中极为活跃的一种有机组分，通过与重金属发生吸附、解吸、络合等一系列作用，对重金属的形态分布、迁移转化、生物有效性等具有重要影响。本项目将界面吸附实验与化学形态模型结合，研究针铁矿-DOM-铅复合体系中铅的界面作用机制。具体研究内容包括：分析不同来源DOM特性、光降解过程，解释了不同来源DOM的特性差异；探索DOM不同组分在针铁矿上的选择性吸附；利用等温吸附、元素分析、自动电位滴定、红外光谱等技术，探索不同来源DOM影响矿物吸附重金属的行为，解释影响因素和吸附机理；构建针铁矿-DOM-铅复合体系的LCD模型；通过模拟光降解，揭示DOM促进抗生素光降解的行为；DOM中低分子量有机酸对土壤P提取。本项目取得的主要研究结果如下：1）不同来源的DOM的腐殖化程度、聚合程度及芳香化程度等指标分散度高，均一性差，湖泊沉积物DOM来源表现为内源和外源的双重特性；2）针铁矿对DOM各组分表现出非均质吸附，高分子组分和疏水性组分被优先吸附到矿物表面；3）DOM更够促进针铁矿对铅离子的吸附，离子强度增大、pH降低有利于吸附进行，DOM能降低针铁矿的zeta电位，增加表面酸性官能团数量，针铁矿-DOM复合体吸附铅的过程中DOM起主导作用；4）LCD模型能够用于拟合针铁矿-DOM-Pb(II)复合体系的Pb(II)吸附；5）DOM对抗生素的光降解起到促进作用；6）DOM中的低分子量有机酸与磷提取效率之间的关系可以用二次多项式方程来解释。本项目初步阐明了DOM对针铁矿吸附铅的影响，揭示铅在针铁矿-DOM-铅复合体系中界面结合机制，为深入了解重金属在土壤和水体环境中的迁移和归宿规律提供数据支持。