National Engineering Laboratory for lake water pollution control and ecological restoration technology, State Environmental Protection Key Laboratory for Lake Pollution Control, Research Center of Lake Eco-environment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
Environ Sci Pollut Res Int. 2018 Jan;25(2):1933-1942. doi: 10.1007/s11356-017-0556-3. Epub 2017 Nov 4.
Nitrogen and phosphorus diffusion at the sediment-water interface is vital to the water quality of lakes. In this paper, N and P diffusive fluxes at the sediment-water interface in Erhai Lake were studied using the sediment-pore water diffusive flux method. Characteristics of temporal and spatial variation of N and P diffusive fluxes were analyzed. Effects of the physicochemical properties of sediments and overlying water were discussed. Results showed that (1) the total N and P diffusive fluxes at the sediment-water interface of Erhai Lake are relatively low. The diffusive flux of ammonia nitrogen is 8.9774.84 mgd m, higher in the middle of the lake, followed by the northern and southern regions successively. The P diffusive flux is -0.0070.050 mgd m, higher in northern region of the lake, followed by middle and southern regions successively. The annual N diffusive flux has two peaks, and the higher peak is in September. The annual P diffusive flux shows a "V-shaped" variation, reaching the valley in July. N and P diffusive fluxes decrease with an increase of sediment depth. Overall, N and P diffusive fluxes at the sediment-water interface in Erhai Lake show different temporal and spatial variation. (2) Aquatic plants promote N and P diffusion at the sediment-water interface in Erhai Lake. The pH, DO, and SD of the overlying water are important influencing factors for the P diffusive flux. P diffusive flux is inversely proportional to the total phosphorous (TP) concentration of the overlying water. The physicochemical environment of overlying water slightly influences the N diffusive flux. The activity of sediments and the organic content are two main influencing factors of N diffusive flux, while P content and morphology of sediments are the main influencing factors of P diffusive flux. Iron and manganese ions are important elements that influence N and P diffusive fluxes at the sediment-water interface. (3) The P diffusive flux at the sediment-water interface in Erhai Lake is mainly affected by the physical and chemical properties of water, whereas the N diffusive flux is mainly influenced by the mineralization of organic matter in sediments. The P diffusive flux at the sediment-water interface is sensitive to the overlying water quality. Sediment transformation from "source" to "sink" was observed in 1 year. On the contrary, N diffusive flux is less sensitive to lake water quality. Endogenetic pollutant control in Erhai Lake should focus on P control.
氮磷在沉积物-水界面的扩散对湖泊水质至关重要。本研究采用沉积物-孔隙水扩散通量法，研究了洱海沉积物-水界面氮磷的扩散通量。分析了氮磷扩散通量的时空变化特征，并探讨了沉积物和上覆水理化性质的影响。结果表明：（1）洱海沉积物-水界面总氮和总磷扩散通量均较低，氨氮扩散通量为 8.9774.84mg·d-1·m-2，湖心最高，依次为北部和南部较低；磷扩散通量为-0.0070.050mg·d-1·m-2，北部最高，依次为中部和南部较低。氮扩散通量的年通量具有两个峰值，较高峰值出现在 9 月；磷扩散通量呈“V”形变化，在 7 月达到谷值。氮磷扩散通量随沉积物深度的增加而降低，总体上，洱海沉积物-水界面氮磷扩散通量呈现出不同的时空变化特征。（2）水生植物促进了洱海沉积物-水界面氮磷的扩散，上覆水的 pH、DO 和 SD 是磷扩散通量的重要影响因素，磷扩散通量与上覆水中总磷（TP）浓度呈反比。上覆水的理化环境对上覆水中总氮（TN）扩散通量的影响较小。沉积物活性和有机含量是影响氮扩散通量的两个主要因素，而沉积物磷含量和形态是影响磷扩散通量的主要因素。铁锰离子是影响沉积物-水界面氮磷扩散通量的重要元素。（3）洱海沉积物-水界面磷扩散通量主要受水理化性质影响，氮扩散通量主要受沉积物有机质矿化作用影响，沉积物-水界面磷扩散通量对上覆水质变化较为敏感，在 1 年内发生了由“源”到“汇”的转变，氮扩散通量对湖水水质变化相对不敏感。洱海内源污染控制应侧重于磷控制。
