BIOGEOCHEMICAL MECHANISM OF POSTDEPOSITIONAL MIGRATION OF Fe AND Mn IN LAKE AHA, CHINA

摘要

Lake Aha in Guizhou Province, China is a medium-sized artificial reservoir with seasonally anoxic hypolimnion. Long-term sedimentary accumulation of iron and manganese resulted in their enrichment in the upper sediments. In anoxic season, Fe~(2+) and Mn~(2+) formed from biological oxidation, would diffuse upto upper water from sediments. However, the concentration of Fe~(2+) increased later and decreased earlier than that of Mn~(2+) . Generally, sulfate reduction occurred at 6 cm below the sediment-water interface. Whereas, in anoxic season, the reduction reached sediment top, inhibiting the release of Fe~(2+) . As the oxidation of Mn~(2+) required molecular oxygen as catalyst, serious anoxia caused the violent diffusion of Mn~(2+). Based on the bio-effects on the accumulation of Mn in natural fresh water, it's necessary to seek a way to control manganese rerelease through accumulated manganese bacteria action.