土壤矿物-有机物-微生物互作界面重金属的化学行为

The representative soil reactive components such as clay minerals, bacteria and humic substance are selected. Experiments of microcosm, long-term soil cultivation with input of heavy metals and field treatments of contaminated soils with organic materials and recombinant bacteria will be conducted. The isothermal adsorption, surface site analysis, attenuated total reflection Fourier transformation infrared spectroscopy (ATR-FTIR), isothermal titration calorimetry (ITC), scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) and X-ray absorption fine structure (XAFS) studies will be employed to investigate the adsorption quantity, affinity, distribution, functional groups, thermal kinetics, atomic separation distances and coordination numbers of Cu, Cd and Pb at the interaction interface of soil mineral-organic matter-microorganims. The binding mechanisms of heavy metals on the interfacial surface of multi-components at the molecular level are elucidated. The transformation patterns of heavy metal species in soil with time, organic matter and microorganisms are characterized. The role and contribution of different soil components in the immobilization of heavy metals could be discriminated. The mathematic models for the immobilization and release of heavy metals in soil are established. Possible strategies for regulating the transformation of heavy metals in soils will be proposed based on both of the environmental factors and soil properties including the content of organic matter and microorganisms that influence the interfacial behavior of heavy metals. The study may facilitate the advances in the research field of soil mineral-organic matter-microorganism interactions and environmental chemistry of heavy metals. The results obtained will also provide scientific basis for the in-situ remediation of heavy metal-contaminated soils.

选取代表性土壤粘粒矿物、细菌和腐殖质，通过微宇宙模拟实验、未污染土壤输入重金属的长时间培养试验，以及重金属污染土壤添加有机物料和重组菌的田间小区试验，借助等温吸附、表面位点分析、红外光谱、等温微量热滴定、电镜-能谱及X-射线吸收光谱等现代分析技术，以Cu、Cd、Pb等重金属为对象，探讨土壤矿物-有机物－微生物互作界面重金属的宏观吸附量、亲和力、分布、化学形态、官能团、热力学特征及键长与配位数等。从分子水平揭示重金属在多组分界面的结合机制与影响因素，摸清土壤中重金属形态随时间、有机物含量和微生物数量转化的规律，明确不同土壤组分在重金属离子固定中的作用和贡献,构建土壤重金属固定与释放的数学模型，根据影响重金属表面行为和有效性的环境因素及土壤有机物和微生物数量等，提出调控土壤重金属转化的方法。推动土壤矿物-有机物-微生物相互作用及重金属环境化学研究的深入，为重金属污染土壤原位修复提供理论支撑。

以三种典型的土壤矿物（蒙脱石、高岭石、针铁矿）、代表性土壤细菌（大肠杆菌E. coli；枯草芽孢杆菌 Bacillus subtilis、恶臭假单胞菌Pseudomonas putida）以及腐殖酸为材料，采用化学平衡吸附，结合原子力显微镜（AFM）、电位滴定、傅立叶变换红外光谱、X-射线吸收精细结构（XAFS）、微区X-射线荧光成像（µ-XRF）以及等温滴定量热技术（ITC）探讨了：1）土壤组分之间的相互作用机制；2）Cd、Pb在微生物及其与矿物-腐殖质复合体等多组分界面的结合特点与吸附模型；3）长时间尺度下土壤中Cu和Cd的形态转化特征与规律。主要获得了以下方面的成果：1）首次在单细胞水平获得了细菌与粘粒矿物间多样的吸附方式及吸附力；2）明确了生长期不同导致细菌在粘粒矿物表面吸附的差异；3）阐明了腐殖酸（HA）在细菌与土壤矿物吸附中的贡献；4）探讨了抗镉真菌（Penicillium sp.）XJ-1对镉的吸附特征及机理；5）构建了矿物-细菌复合体对Cd吸附的表面络合模型；6）揭示了Cd与Pb在蒙脱石-细菌复合体上的分配和竞争吸附规律；7）初步阐明了矿物与细菌复合体表面镉的结合特征与机制；8）明确了在较长时间尺度下，有机物和微生物的增加引起土壤中Cu和Cd向稳定有机结合态转变的规律。为重金属污染土壤的风险评估以及土壤修复措施的制订提供了科学依据。发表 SCI论文22篇，主编出版SCI专刊1期, 召开第21届环境生物地球化学国际学术会议。参加国内外学术会议12次，做口头报告11次。培养博士和硕士研究生8名。