秸秆腐殖化对铅/镉在黄土分形组分界面异质性吸附的非生物调控机制

Straw incorporation is regarded as an important approach for straw recycling in the “twelfth five-year plan” of China, and the investigation of released humification component from straw on the transformation behavior of heavy metals has attracted much more attention these years. The co-contaminated loess by lead and cadmium is applied in the research as the experimental samples to reveal the controlling mechanism of adsorption/complexation on loess component interface in the humification process. The litter bag method is used to indicate the releasing and transformation properties of the humification component, including humic acid (HA), fulvic acid (FA) and dissolved organic matter (DOM). The selective extraction methodology (SEM) and response surface methodology (RSM) are involved to optimize the separation process of loess component of clay minerals, organo-mineral complex, HA/FA, DOM, manganese oxides and manganese/iron-manganese oxides, and the products are analyzed with spectral instruments. The adsorption/complexation mechanism of lead and cadmium on loess component in humification system is described with adsorption experiment, modeling illustration and instrumental measurement. The achievements are valuable to reveal the interface combination nature of heavy metals and soil system with continuous input of exogenous organic matter, and significant for contaminated soil remediation and related subjects development.

秸秆还田是国家“十二五”期间秸秆资源化利用的重要导向，秸秆腐殖化产物对土壤重金属迁移转化行为的调控作用是值得关注的关键问题。本项目以铅/镉复合污染黄土为研究对象，围绕秸秆腐殖化过程对重金属/黄土组分界面吸附/络合行为调控机制这一科学问题展开研究。采用尼龙网袋法和光谱技术跟踪识别秸秆腐殖化产物（胡敏酸、富里酸和可溶性有机质）的生成特性和转化规律；引入选择性萃取分离法和响应曲面法优化黄土主要组分（粘土矿物、有机无机复合体、胡敏酸/富里酸、可溶性有机质、锰/铁锰氧化物）的提取过程并进行产物性质表征；结合吸附实验、模型验证和仪器检测手段揭示腐殖化体系铅/镉/黄土组分吸附/络合行为差异的内在机制。本项目对于深入明确外源有机质连续输入条件下重金属/土壤体系的结合本质具有重要意义，相关成果有利于拓宽土壤污染化学精细化研究的切入面并促进学科交叉和发展。

有机质共存条件下重金属/土壤组分结合行为和转化机制研究具有重要的理论意义和现实意义。系统分析黄土理化性质并对秸秆腐殖化产物进行表征，探讨不同操作条件对腐殖化产物的微观影响。借鉴SSSA、SSSC和IHSS推荐的方法分离粘土矿物、有机无机复合体和铁锰结核三种黄土主要组分，对提取产物进行全面识别鉴定。采用等温线和动力学模型探讨三种分离产物与铅/镉的结合行为，研究反应条件对实验结果的影响。利用修正型Stern-Volumer方程揭示铅/镉与溶解性有机质的配位过程，Gibbs-Heimhaltr方程分析反应热动力学特性，Tessier连续提取法研究铅/镉的形态转化及与溶解性有机质的响应关系。以黄土区金盏菊根际圈土壤溶解性有机质为实测样本，综合多种光谱或波谱表征手段，包括SEM、FT-IR、XRD、ICP-OES、NMR、Raman、UV-Vis、XRF、3D-EEMs等，明确溶解性有机质与铅/镉的结合行为及对反应过程的调控机制。本研究为揭示有机质干扰下黄土铅/镉迁移转化行为机制提供了关键信息，有助于污染黄土修复技术的理论完善和升级改造。项目资助已发表学术论文11篇（其中SCI收录9篇）；授权国家发明专利4项；获各级各类奖项3项；参加学术会议(或进修)4次；培养硕士研究生3名（全部取得硕士学位）。