Studyon Characteristicsof Sediment,Overlying Water Pollution And Sediment Phosphorus Releasein Nanhu Lake

Sediment is not only a habitat for plants and animals in lakes,but also an important pool of nutrients and other pollutants.Under certain conditions,nutrients in the sediment will be released into the overlying water,seriously affecting the water quality.In this study,the spatial and temporal distribution and contamination characteristics of nutrient in the water column and sediment,and the sediment phosphorus release kinetic and potential were studied by means of field investigation and experimental simulations,and the main results are as follows.There are obvious differences in the spatial and temporal distribution of nutrient concentration in the water column of Nanhu Lake.With the change of seasons(summer-autumn-winter),the concentration of total nitrogen,total phosphorus,orthophosphate,chlorophyll a and permanganate index showed a decreasing trend.Among the 9 sampling sites,the nutrient concentrations at the sites located in the sub-lake area were higher than those in the main lake area.There are differences in the vertical and horizontal distribution of nutrient concentrationin the sediment and interstitial water.In the depth range of 0-25 cm,the total nitrogen content of sediment decreased with depth,while the total phosphorus content of sediment increased with depth in the range of 0-15 cm,and then decreased with depth in the range of 15-25 cm.In the depth range of 0-25 cm,the interstitial water total nitrogen concentration increased with depth in the range of 0-20 cm,showing a strong sedimentation trend,and decreased in 20-25 cm.The interstitial water total phosphorus concentration increased with depth in the range of 0-10 cm,and decreased with depth in the range of 10-25 cm.The concentration of total nitrogen and total phosphorus in the interstitial water was higher than that of overlying water in autumn and winter,indicating a gradient risk that the total nitrogen and total phosphorus of the sediment may be released through the interstitial water to the overlying water.The results showed that the maximum release and release potential of sediment phosphorus were significantly and positively correlated with the interstitial water concentration and sediment content.The release kinetics and release potential of sediment differed greatly at different sites,and the release potential is mainly manifested by the increase of the water-soil mass ratio.