Factors of high total phosphorus concentration in the Nanchang typical area of Poyang Lake
In this study,the Nanjishan national monitoring site(NJS site)and its confluence area were selected to explore causes of the high TP concentration through the field investigation of the water environmental factors and sediments.Results indicated that the TP exceedance in the surface water mainly occurred in the low lake water level period(LLP)and lake discharges period(LDP),with the exceedance multiples of 3.06 and 2.78 times,respectively;and TP concentration was significantly correlated with dissolved organic matter(DOM)and turbidity.Three-dimensional fluorescence spectroscopy(3D-EEM)regional integration method and parallel factor analysis(PARAFAC)showed that the DOM consisted of three components,which were dominated by humus-like substances such as fulvic acid(partition Ⅲ,components C1and C2),and the main source of which was the degradation of wetland plant litter,with the highest proportion(55.74%)in the LLP.The proportion of protein-like substances(partition I and component C3)increased to more than 35%during the RDP due to inputs of the confluence tributaries and the neighboring disc-shaped lake.TP showed a significant positive correlation(P＜0.05)with humic organic matter and a significant negative correlation(P＜0.05)with proteic organic matter,indicating that TP and humic organic matter have a common origin.TP and turbidity showed a significant positive correlation(P＜0.05),and the highest turbidity was observed in LLP(mean value of 320.83NTU),during which the tributaries and the disc-shaped lake were cut off.The sediment substrate in the study area was chalky,dominated by fine components,and the median grain size DX(50)belonged to fine chalky(2～16µm);the range of sorting coefficients was 2.11～2.75,with poor sorting;the sediment samples were mostly located in the bottom-side suspended and homogeneous suspended transport area,with weak sedimentary hydrodynamics and weak transport capacity;the suspended particulate matter that was not easily deposited,resulting in high turbidity.The average TP content of 0～5cm surface sediment was high(527.89mg/kg),and sediment P was released to the overlying water,with the largest P release flux(0.21mg/(m2·d))in the NJS site,indicating that surface sediments was one of the important influences on TP concentrations in the site waters.
Poyang Lakesurface water qualitydissolved organic mattersedimentgrain size parameters
万方数据
维普
