Biogeochemical Effect on Postdepositional Remobilization of Fe-Mn in Lake Aha, Guizhou Province

Abstract

贵州阿哈湖是一底层滞水带季节性缺氧的中型人工湖.由于长期积累.沉积物顶部微粒悬浮层出现了Fe、Mn富集.湖底缺氧时,经生物氧化作用形成的Fe²⁺、Mn²⁺自沉积物向上覆水体扩散,水体Fe²⁺浓度增高比Mn²⁺滞后出现且超过前结束.沉积物中硫酸盐还原作用一般在沉积物-水界面以下6cm深度内进行,但在缺氧季节上移至沉积物顶部,并抑制了Fe²⁺的释放.还原态Mn²⁺的氧化作用需分子氧参与.缺氧导致Mn的扩散迁移.基于天然水体中存在聚集Mn的生物效应,可寻求一条通过Mn细菌凝聚作用来控制Mn二次释放的途径.;Lake Aha, located in the suburb of Guiyang? Guizhou Province, is a medium artificial reservoir with seasonally anoxic hypolimina. After a long-term accumulation, iron and manganese are enriched in the upper sediments. When waters of oplimnion and hypolimnion are anoxic in late summer and early autumn, Fe²⁺and Mn²⁺ formed by biological respiration, are diffused upto the overlying waters from the sediments. However, the concentration of Fez+increases later and se-creases earlier than that of Mn²⁺. Generally, sulphate reduction takes place within 6cm depth of the sediments. Whereas in the anoxic season, the reduction reaches the upper sediment, inhibiting the diffusion of Fe²⁺. Meanwhile? manganese oxidation needing molecular oxygen as catalyst, causes the violent diffusion of Mn²⁺. Because manganese can be accumulated by microorganism in natural fresh water, it is important to seek method to control manganese remobilization through manganese accumulated action.