湖泊沉积物中铁异化还原对界面磷再生的影响机制研究

The process of microbial dissimilatory Fe(III) reduction plays a key role in governing the cycling and regeneration of organic and inorganic phosphorus at the water-sediments interface especially during the redox boundaries seasonal variation. Considering the important effects of this process in environmental geochemistry, this project focuses on the regeneration mechanism of organic and inorganic phosphorus on the water-sediments interface driven by the process of microbial dissimilatory Fe(III) reduction. Taking Lake Wuliangsuhai as the studied area, which characterized as obvious seasonal hypoxia, the dynamics of iron and phosphorus fractions across the water-sediment interface will be characterized according to the in situ investigation every week during the ice-covered period, then the systems of “sediments (inactivated) - iron reduction microbial - iron oxide - phosphorus” and “sediments (inactivated) - iron oxide - phosphorus” will be established to study the key factors and mechanism impacting phosphorus regeneration during the dissimilatory reduction process of iron oxides at the water-sediments interface. Meanwhile a new operation definition of “truly dissolved size fraction (<0.02µm)” is introduced in this work to make an effort to understand the interface behavior of iron and phosphorus more accurately. Accordingly, the project presents important innovations due to the introduced new ideas, methods and theory, especially considering the coupling effects of the dissimilatory reduction of iron oxides and the regeneration of organic and inorganic phosphorus at the water-sediments interface during the redox boundaries seasonal variation. Based on this project, it will help to insight the environmental effects of iron oxides on phosphorus at the water-sediment interface during the redox boundaries seasonal variations in lakes from the cold and arid area of China, and to find the critical condition of iron oxides acting as phosphorus sink or source. Otherwise, the project can accumulate data set on integrated control of lakes pollution at the condition of environment change, which also provides scientific references on the lakes protection and resource development of Inner Mongolia.

湖泊水-沉积物界面铁异化还原对界面磷再生的影响机制具有重要的环境效应。本项目引入“溶解态”的新操作定义，以铁氧化物的环境效应为切入点，以季节性缺氧明显的乌梁素海为研究对象，以水-沉积物界面铁氧化物与磷的形态动态特征为基础，以铁氧化物对磷界面行为的影响机制为主线，构建“沉积物（灭活）-铁氧化物-磷”和“沉积物（灭活）-铁还原微生物-铁氧化物-磷”两种模拟体系，系统开展铁异化还原对界面磷再生循环的影响机制研究，在立意、研究思路与方法等方面均有显著创新。本研究对理解寒旱区湖泊沉积物中铁氧化物在氧化还原边界层季节性迁移中的控磷机理，明确湖泊环境中铁氧化物对磷源汇功能转换的临界条件，全面理解铁氧物异化还原对有机磷界面行为及再生循环的影响机制，完善“微生物-铁-磷”耦合的环境地球化学循环方面的基础理论和研究思路等均具有重要的科学价值，对丰富我国寒旱区湖泊富营养化治理的控磷方法等具有借鉴作用。

项目绕着拟解决的关键科学问题与预期研究目标，采用连续提取法和XRD技术，验证了乌梁素海积物中铁氧化物的主导形态与可提取态铁间的响应关系，FeU和FePRS是沉积物中铁的主要赋存形态，分别占FeT含量的46.7和33.5%，并有FeU>FePRS>Feox2>Fecarb>Feox1>Femag的含量序列。分析了不同湖泊沉积物中P/Fe化学计量比的差异性特征，总结归纳了湖泊环境中铁氧化物对磷源/汇功能转换的环境条件及其耦合效应，不同湖泊沉积物的释磷能力序列为：武汉城市湖泊>太湖>鄱阳湖>博斯腾湖>岱海>大龙池>乌梁素海>呼伦湖。从沉积物中分离纯化了3株铁异化还原菌株，并进行16SrRNA基因序列分析鉴定，构建了上覆水-孔隙水-沉积柱芯微宇宙系统，开展了长时间尺度不同季节不同微生物种类驱动下铁异化还原对磷再生循环影响机制的微宇宙模拟实验研究，确定了冰封期表层沉积物孔隙水（0-5cm）温度、pH、Eh的范围分别为：1-4℃、7.0-7.5、-470--220mv；上覆水-孔隙水-沉积物系统中的IP和Fe2+具有较好的浓度响应关系，表明微生物添加组对铁氧化物的异化还原及有机磷的降解均较强，导致沉积物向上覆水释放IP的趋势显著。基于氧化还原序列分层添加的微宇宙实验模拟系统清晰地刻画了各氧化还原带中相应还原菌株驱动下的铁与磷生物地球化学耦合循环过程与机制，沉积剖面上铁还原带（8-10cm）中磷的释放潜力更大，是释磷的热点层位，对上覆水的营养盐浓度有较大的潜在影响。研究发现，并非所有微生物添加组的铁与磷均表现出同步释放的趋势；硝酸盐还原菌倾向于降解有机质和有机磷而释磷，异化铁还原菌等更倾向于还原溶解铁氧化物而释放铁结合态磷，揭示不同微生物在不同温度下释磷机理及释磷来源的差异性；厘定了冰封期与非冰封期水-沉积物界面生物地球化学动态的差异性特征，提出了耐冷微生物驱动下元素界面行为的环境效应对春季藻类生长启动阶段营养供给的重要认识。. 项目在完成计划任务的同时也开展大量的拓展研究，获得各类实验数据15000多个，发表SCI论文6篇，全面完成了预期目标。