干湿交替驱动下洲滩湿地沉积物中溶解性有机质（DOM）与重金属结合机制研究

Structural evolution of dissolved organic matter (DOM) in the alternate wetting/drying cycles extremely complicates and challenges the behavioral analysis of DOM binding with heavy metals in beach wetland sediments, which is the focus of soil, environment and ecological science field. Based on the typical characteristics of “alternate wetting/drying cycles” in the wetland of Dongting Lake, this project is to analyze binding interactions of DOM with heavy metal (Cd and Cu) in beach wetland sediments. This work could be done by using various test means(e.g. spectral quenching titration, equilibrium dialysis, and potentiometric titration), multiple detection techniques(e.g. spectrum, mass spectrometry and microscopic observation), and abundant analysis methods (e.g. chemometrics analysis and complexation model). To reveal the coupling relationship of alternate dry-wet cycles - DOM structure - binding rules of DOM and heavy metals. We investigate the evolution characteristics of DOM composition structure in the process of alternate wetting-drying in beach wetland sediments from both apparent and molecular levels; elucidate the correlation between the structural evolution of DOM and the morphological changes of heavy metals; clarify the effect of alternating dry-wet environment on the interaction between DOM and heavy metals and their mechanisms. Hence, this research will be the theoretical basis for the study of the ecological environmental behavior of DOM and heavy metals in beach wetland, as well as the theoretical guidance for the environmental risk assessment and remediation of heavy metal pollution.

干湿交替过程伴随的溶解性有机质（DOM）组成结构变化使得洲滩湿地沉积物中DOM结合重金属行为的解析极具复杂性和挑战性，是土壤、环境和生态科学领域关注的焦点和热点。本项目基于洞庭湖洲滩湿地“干湿交替”的典型特征，以洲滩湿地沉积物中DOM与重金属Cd、Cu为研究对象，通过野外调查采样，利用光谱滴定、平衡渗析、电位滴定等试验手段，光谱、质谱、显微观测等检测技术，辅以化学计量学、络合模型等分析方法，结合表观和分子两个层面探讨洲滩湿地沉积物干湿交替过程中DOM组成结构的变化过程，探究沉积物DOM组分特征与重金属形态的科学关联，阐明干湿交替环境下沉积物DOM结合重金属的分子机理，揭示干湿交替-DOM组成结构-DOM结合重金属三者之间的耦合机制。研究成果有助于完善洲滩湿地沉积物DOM与重金属环境地球化学过程的相关理论，对洲滩湿地环境风险的评估和重金属污染的修复具有重要的实践意义。

解析干湿交替驱动下沉积物溶解性有机质（DOM）组成结构演变规律及其与重金属分子结合机制是明确洲滩湿地沉积物中碳循环的关键。本项目基于洞庭湖洲滩湿地“干湿交替”典型特征，以洲滩湿地沉积物DOM与重金属为研究对象，基于响应面模型和改进神经网络方法构建了重金属Cd吸附模型，明确了DOM组成和浓度是控制Cd在沉积物表面物理化学迁移过程的关键因素；借助高分辨质谱技术结合重金属形态分级提取技术，探究了沉积物干湿交替下DOM分子组成变化规律、重金属形态变化特征、DOM与重金属响应关系，发现干湿交替过程中沉积物DOM中芳香性物质保留以及N和S元素释放/消耗机制是调控重金属行为的关键；结合多种光谱学技术，阐明了磷酸盐共存条件下DOM对重金属迁移的影响机制，发现了磷酸盐与DOM的竞争机制会相互限制其与重金属的相互作用；通过根箱培养试验结合化学计量学分析，探究了水分条件变化与根际环境共驱动下重金属与沉积物DOM的结合效应与机制，提出了铁氧化物与富里酸共存对重金属向根表迁移的促进机制；基于吸附与共沉淀反应，构建了富里酸-铁氧化物-重金属三元耦合反应体系，发现了富里酸分子中多糖C-O基团与羧基O=C-O是连接铁氧化物与重金属的关键结合位点，相较于富里酸-铁氧化物吸附型复合物，其共沉淀型复合物结合的重金属具有更低的有效性。基于洲滩湿地沉积物中DOM-矿物-重金属三者环境效应，评估了三种不同晶型锰氧化物（δ-MnO2, γ-MnOOH和Mn3O4）对重金属污染沉积物的修复效果，发现沉积物中可浸出Cd、生物可提取态Cd以及酸可溶态Cd浓度分别减少43.9%–66.81%、45.16%–99.40%和27.55%–35.49%，这归因于Mn-O官能团络合等关键机制。本项目研究成果对洲滩湿地沉积物中DOM与重金属环境地球化学循环过程研究提供了重要的理论支撑，对洲滩湿地环境风险评估、沉积物污染预防和重金属污染沉积物修复具有重要的实践意义。基于上述研究工作，本项目在Water Research、Journal of Hazardous Materials、Environmental Pollution等期刊发表论文18篇，圆满完成了各项既定任务指标，也获得了国内外广泛关注与引用。