微电场-人工湿地修复水体重金属污染的效果和机理及优化调控

In our country, effective and environmental methods for waterbody heavy metal restoration are deeply demanded. In this proposal, complementary advantages of electrochemical technique and constructed wetland has been creatively coupled to build a new treatment system called "micro-electric field constructed wetland" which aims to enhance the restoration of water body heavy metal pollution obtaining better ecological and economical effectiveness. Firstly, The impacts of applying micro-electric field on the wetland plant physiological processes and heavy metal absorption will be investigated to obtain suitable electric field conditions and dominant plant species. Furthermore, microbial ecological techniques such as Terminal Restriction Fragment Length Polymorphism (T-RFLP), Phospholipid Fatty Acid (PLFA) Analysis, Polymerase Chain Reaction - Denaturing Gradient Gel Electrophoresis (PCR-DGGE) will be applied to analyze the impact of micro-electric field on the microfloral evolution and structure. Meanwhile, the synergism between wetland plant and microbial in removing heavy metal will be explored. Additionally, heavy metal speciation and quantity in substrate, water phase and deposits will be analyzed to reveal the changes of maximum absorption and absorption-desorption equilibrium brought by micro-electric field application. Together with regular water quality analysis, the heavy metal speciation transportation and transformation in substrate will be further studied. Finally, through identifying the key influences of heavy metal removal in coupled system, optimization and controlling measures will be put forward for achieving the optimal restoration. The findings and out-comings will enrich the scientific and technological supports for micro-electric field constructed wetland as a new technique in restoring water body heavy metal pollution.

国内缺乏高效、生态环保的水体重金属污染修复方法。本项目创新性地将电化学处理与生态工程技术进行优势互补，提出微电场-人工湿地耦合系统，提升人工湿地对水体重金属污染的修复效果。通过研究施加微电场对湿地植物的生理指标和对重金属吸收特性的影响机理，得出适宜的电场条件和优势种；运用16sRNA基因末端限制性片段分析、磷脂脂肪酸和多聚酶链式反应-变性梯度凝胶电泳等微生物生态学技术，解析微电场对微生物群落结构影响，并阐释植物、微生物去除重金属的协同效应；分析施加微电场前后人工湿地基质、水相和沉积物中重金属元素的化学形态和含量，并结合常规水质指标分析，揭示微电场对基质最大吸附量和吸附-解吸平衡浓度的影响，探明耦合系统基质中重金属形态的时空变化及迁移转化规律；识别影响耦合系统去除重金属的关键因素，提出优化调控措施，获得最佳处理效果；成果将为微电场-人工湿地耦合系统修复水体重金属污染提供科学依据和技术支撑。

发挥电化学与人工湿地优势，建立微电场-人工湿地处理系统，提高水体中重金属元素的吸收，强化重金属污染水体的修复作用。首先，研究施加微电场对湿地植物的生理指标和对重金属吸收的特性，得出适宜的电场条件和优势植物种。发现低强度电流能增强植株生理机能，而高强度电压则抑制植物生长、降低抗逆能力，3V左右电压最有利于植物生长，对比之下香蒲和水葱受到电流刺激作用最强；重金属Cu、Pb、Cd、Zn在湿地基质中的含量存在很大差别，重金属含量大小顺序为：Pb>Cu>Cd>Zn，在湿地植物中含量大小的排序皆为：根部>茎部>叶片。其次，运用16sRNA高通量基因测序分析，解析微电场对微生物群落结构影响，并阐释植物、微生物去除重金属的协同效应。发现在电场作用下体系中Thiobacillus和Thauera等具有较强反硝化作用的群落丰度较对照明显增加，在根系和电流作用下微生物群落多样性增加，进一步促进了对重金属的去除；再者，通过正交实验，分析了电压、通电时间、水力停留时间对耦合系统去除重金属的影响。结果表明，其影响作用为电场电压>水力停留时间>通电持续时间，优选条件为电场电压4V、通电持续时间12h以及水力停留时间48h。在最优条件下，引入电场后，人工湿地中发生电解、氧化还原、絮凝、沉积等作用，一定程度上增强了系统净化能力，提高了重金属去除率，与传统人工湿地相比，电场人工湿地对重金属Cu、Pb、Cd、Zn的平均去除率分别提高了2%、0.5%、10%、28%。成果将为微电场-人工湿地耦合系统修复水体重金属污染提供科学依据和技术支撑。