三峡水库消落区土壤磷素释放与富营养化

Eutropication and phosphorus release of soil in drawdown area ofThree Gorges reservoir

三峡工程建成后,其独特的水库调度方式将在库周形成垂直距离为30m的消落区,淹没陆地面积632km2。消落区土壤受库水周期性的淹没、出露、冲刷、淤积,加上耕作和施肥影响,将形成一个脆弱生态系统。湖库消落区土壤是污染物的源或汇。消落区土壤磷素释放对水体富营养化有重要影响。研究消落区土壤磷负荷及其释放机制,可以为水库磷负荷提供基础数据,给消落区土地利用方式提供决策依据。淹水土壤磷素释放是与多个因子相关的复杂过程。本文分析了消落区土壤磷释放对富营养化的潜在影响,综述了土壤磷素释放的影响因素:磷形态、有机质、铁、铝、pH、温度和微生物。重点讨论了土壤在淹水—干燥—淹水条件下土壤性质变化和土壤磷素释放机制。一般认为,土壤淹水后,土壤氧化还原电位降低,提高了磷的有效性,促进了磷释放。干—湿交替比连续淹水释放磷是增加或减少,目前还存在争论。

After the completion of three gorges project, the special attemperation of water will make a 30-meter-high drawdown area, which is 632 km^2. Flooded, revealed, washed, deposited periodly by the water in the reservoir and the farming and fertilization, the soil of drawdown area will become a breakable ecosystem. The soils in the drawdown area of reservoir or lake are source or sink for pollutants. Phosphorus release of soils in the drawdown area strongly affected eutrophication of water column. Studying the load and release mechanism of phosphorus in soils may offer basic data of phosphorus loading in the reservoir and decision data of land using. Phosphorus release in flooding soils is a complex process, which is related to many factors. This paper analyzed the potential effects of phosphorus release on eutropication, including phosphorus forms, organic matter, iron, aluminum, pH value, temperature and microbes. Mainly discussed the changes of soil properties and the release mechanism of soil phosphorus under flooding-drying-flooding conditions. In general, the soil flooded will decrease the Eh, improve the availability and release of phosphorus. The release of phosphorus under drying-flooding alternation is more or less than that under successive flooding is on debate.