三峡库区消落区表层沉积物磷吸附特征

Phosphorous adsorption characteristics of upper layer sediments in the water level fluctuating zone of Three Gorges Reservoir area

以三峡库区消落区表层沉积物为研究对象,通过对干湿交替沉积物中磷的赋存形式、吸附等温曲线的分析,揭示了干湿交替过程中沉积物磷的分布规律、吸附特征以及磷的源汇变化。结果表明:上覆水总磷变化呈现11月总磷<5月总磷<8月总磷。消落区覆水到出露沉积物最大磷吸附量、土壤最大缓冲能力在增加,磷零吸持平衡浓度、易解吸磷在降低,表明沉积物在夏季出露落干的过程中,固磷能力增强,释磷能力减弱;消落区土壤首次覆水过程中土壤磷呈现出由源到汇的转变。成库初期,覆水时沉积物主要表现为磷的积累,次年水库开闸放水排沙时,消落区表层富磷沉积物被冲刷排出。

The upper layer sediment in the water level fluctuating zone of Three Gorges Reservoir area （TGRA） is studied through an analysis of phosphorous forms and adsorption isotherm curves in the fluctuating zone with wet-dry cycles. The result shows that the total phosphorous （TP） content for August would be higher than of May in the overlying water, while the lowest value is found in November. The max adsorption quantity of phosphorus and the max buffer capacity of soil of sediments increase while their equilibrium phosphorus concentration and reactive desorbed phosphorus drop when sediments alternated from the submerged state to the exposed state, which indicates that phosphorous fixing strengthens whereas phosphorous releasing weakens in the exposed sediments in summer. Moreover, in the course of being submerged for the first time, sediments phosphorous show an alternation from a source to a sink. During the initial stage of impoundment of Three Gorges Reservoir, phosphorous is being accumulated in the sediment. This phosphorous-enriched upper sediment layer in the water level fluctuating zone will be washed away with reservoir sluicing in the following year.