鄱阳湖水位对沉积物磷释放的影响及总磷考核建议

Study on release potential of sediment phosphorus under water level fluctuation in Poyang Lake and suggestions on assessment

为探讨干湿交替对湖泊沉积物内源磷释放的影响,结合基础资料和模拟试验,研究了鄱阳湖水位波动及其驱动下沉积物中磷的释放过程,并对湖区总磷(TP)考核提出建议。结果表明:2020~2022年鄱阳湖星子站水位高幅波动,最高水位差分别为15.01,11.42 m和12.69 m,导致水面面积也呈现高度动态性,最低水位时的裸露面积分别达到3433.92,3442.40 km^(2)和3618.36 km^(2),大面积沉积物会经历干湿交替过程;沉积物磷释放模拟试验结果显示,南矶山和青岚湖断面沉积物经历裸露-暴晒-淹水后,淹水初期沉积物TP的平均释放通量分别高达16.67 mg/(m^(2)·d)和13.23 mg/(m^(2)·d);综合考虑鄱阳湖水体中TP组成特征和水位波动的影响,建议湖区国控断面以活性磷酸盐(SRP)或者溶解性总磷(TDP)替代TP作为磷考核指标,并动态调整磷考核标准的阈值,当星子站水位低于11.00 m时以河流标准考核。

In order to investigate the effect of alternation of wetting and drying on phosphorus release from lake sediments,this paper studied the process of phosphorus release from sediments driven by water level fluctuation of Poyang Lake based on basic data and simulation test,and gave some suggestions for total phosphorus(TP)assessment of the lake.The results showed that the water level of Xingzi Hydrological Station fluctuated in 2020~2022,and the maximum water level difference were 15.01,11.42 m and 12.69 m,respectively,resulting in a highly dynamic lake area.The exposed area at the lowest water level reached 3433.92,3442.40 km^(2) and 3618.36 km^(2),respectively,with a large area of sediments experiencing the alternation of wetting and drying.The results of simulation test showed that the average TP release fluxes from the sediments of Nanjishan and Qinglan Lake sections experienced bare-exposure to sunshine-flooding were 16.67 mg/(m^(2)·d)and 13.23 mg/(m^(2)·d),respectively,in the early stages of simulation.Considering the characteristics of TP composition and the influence of water level fluctuation in Poyang Lake,it was suggested that soluble reactive phosphate(SRP)or total dissolved phosphorus(TDP)should be used as the phosphorus assessment parameter instead of TP for Poyang Lake,and the threshold should be dynamically adjusted.When the water level of Xingzi Hydrological Station was lower than 11.00 m,the river standard should be used for the assessment.