西南岩溶地下河悬浮颗粒物中铁物种的协同效应和铁循环调控机制

As a source of drinking water, pollution of the southwestern karst Subterranean river is a major environmental problem of water body. Making full use of natural conditions and laws to purify environmental pollution is a research hotspot and development trend in the field of environmental protection. This project would use the iron-containing substances of suspended particulates from the karst underground river in Guangxi as the iron cycle species, and choose nitrite (nitrogen) and hydrophosphate (phosphorus) as the targeted pollutants for redox reactions and adsorption reactions, respectively. In view of the key scientific issues in the research on purification of groundwater contaminants that are currently centered on the iron cycle, the specific contribution of iron species to the migration, transformation and fixation of N and P in the iron cycle system would be studied. The main effective pathways on iron recirculation processes affecting by the migration, transformation, and fixation processes of N and P would be determined. This study would also propose and validate strategies for coordinated regulation of the iron recirculation system for migration, transformation and fixation processes of N, P by iron species variation in the karst subterranean river. This study is based on the synergistic effect of iron species in suspended particulates for nitrogen and phosphorus purification in the karst subterranean river. We aim to explore the iron regulation mechanism for purification of targeted pollutants by iron species, and to provide theoretical basis and practical methods for an in-situ remediation technology for polluted water using subterranean iron regulation system.

西南岩溶地下河饮用水源污染是水体重大环境问题。充分利用自然条件和规律净化环境污染是环保领域的研究热点和发展趋势。针对目前以铁循环为核心的地下水污染物净化研究的关键科学问题，本项目以广西岩溶地下河悬浮颗粒物含铁物质为铁循环物种，以亚硝酸盐（氮）和磷酸氢盐（磷）分别作为氧化还原反应靶向污染物和吸附反应靶向污染物，具体研究铁循环体系中铁物种对N、P的迁移、转化、固定作用的贡献比重；确定N、P的迁移、转化、固定过程分别对悬浮颗粒物中铁循环过程影响的主要途径；提出并验证地下河环境中悬浮颗粒物的铁物种对N、P迁移、转化、固定过程的铁循环体系协同调控策略。本研究基于岩溶地下河悬浮颗粒物中铁物种的氮、磷净化铁循环协同效应，探讨外源铁物种对目标污染物净化的铁循环调控机制，为利用地下河铁循环体系原位修复污染水体提供理论依据和实践方法。

灵水和罗波潭是广西武鸣岩溶盆地位中最大的两个地下水水系和饮用水水源地一级保护区。本项目在罗波潭及灵水泉口过渡带开展了悬浮颗粒物/表层沉积物中铁循环对氮磷污染影响控制机制研究，以期为利用悬浮颗粒物/表层沉积物中铁循环对水源地进行保护提供理论支持。通过水样指标检测、沉积物氮磷成分检测，结合扫描电镜（SEM）、BET比表面积、X射线衍射光谱（XRD）和X射线光电子能谱（XPS）等材料科学研究手段，较全面地认识了灵水和罗波潭泉口水和物质环境特征。灵水和罗波潭的铁背景值较高，灵水的地下水出口的表层沉积物中含有大量铁结合态磷和铁结合态铝，说明沉积物中的铁物种对氮磷固定、降低水中氮磷浓度有重要作用。.SEM和比表面积结果表明，灵水和罗波潭两处的悬浮颗粒物形貌为层状不规则颗粒物；说明粘土矿物是两处地下水悬浮颗粒物的主要成分。XRD中并未得到含铁铝结晶成分，说明与氮磷结合的铁铝物种主要以无定形形态存在，而石英石等粘土矿物则因其层状结构提供的比表面积为悬浮颗粒物在地下水系统中运输提供了良好的载体。XPS研究表明，悬浮颗粒物中的Fe和Al以氧化态的形式存在，但没有出现P的特征峰，说明了P物种在岩溶泉口交互带更倾向于储存在沉积物中，一旦沉积物由于水动力的影响成为悬浮颗粒物，P物种也随之释放到环境中。.原位高分辨薄膜扩散梯度技术（DGT）研究发现，Fe(II)浓度与泉口距离成反比，表层沉积物上覆水的物质活性程度显著。说明灵水地下水环境有利于活性Fe(II)物种的存在，是天然的Fe（II）循环研究场。.两处研究地的悬浮颗粒物的吸附动力学研究表明，两处颗粒物对氨氮、硝态氮及磷的吸附均由吸附质分子向吸附剂表面扩散这一过程决定。而且，两处颗粒物对硝态氮的吸附量最小，对磷的吸附量要大于氨氮的吸附量。这可能是由于颗粒物中含有的金属水合氧化物对磷的阴离子形态有较好趋向性。在pH、腐殖质、溶解氧三个条件影响因子中，腐殖质对促进颗粒物对氮磷的吸附作用，而另外两者影响不明显。.