阿哈湖Fe、Mn沉积后再迁移的生物地球化学机理

BIOGEOCHEMICAL EFFECT ON POSTDEPOSITIONAL REMOBILIZATION OF Fe-Mn IN LAKE AHA, GUIZHOU PROVINCE

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 Fe2+ increases later and secreases 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.