Study On Distribution And Release Of Nutrient From Sediments In Ulansuhai

Lake wetland sediment is one of the three main components of aquatic ecosystem,and it is also an important material host in water bodies.In lake ecosystems,sediments play an important role in the"source-sink"effect of pollutants in overlying waters.After the reduction of external pollution control,endogenous pollution is the main source of pollution in water environment system.Effective control of internal pollution has become a key issue in water environment system governance.The deterioration of aquatic ecological environment in Ulansuhai Lake is becoming more and more serious,and many negative impacts follow.It is urgent to remediate aquatic ecosystems.A lot of research has been carried out by researchers and then corresponding engineering measures to effectively control the external pollution have been taken by maintenance managers.But the eutrophication of water quality is still serious,therefore the treatment of internal pollution has become particularly important.In this paper,the sediment of Ulansuhai Lake was studied to simulate and analysis the release of nutrient from sediments by laboratory experiments,which basic on consulting a large number of relevant overseas and domestic research status,collecting research data and field monitoring.The sediment thickness of Ulansuhai was uneven distribution for the hydrodynamic conditions of lakes,the distribution of ancient rivers and the location of rivers entering the lake.The maximum thickness was over 2.17 meters,and the minimum was about 0.20 meters.The average thickness of the whole lake was0.88 meters.Sedimentary silt accumulation was 397.722 million tons,which was influenced by the source and distribution of sediments,the silting-promoting effect of aquatic vegetation and the action of wind and wave.There were obvious spatial and temporal differences in sediment deposition of Ulansuhai Lake.Organic nitrogen was the main form of nitrogen in sediment of the Ulansuhai Lake.The horizontal distribution of total phosphorus varied greatly under the influence of hydrodynamic conditions and sedimentary environment.In the vertical direction,the distribution of total nitrogen was obvious that it decreased with the increased of depth and the regression of agriculture,production and living had obvious influence on nitrogen deposition.The vertical distribution of total phosphorus was significantly different,which was related to human activities,environmental factors,early evolution and diagenesis.According to the organic pollution index,most of the areas are in the state of organic pollution by calculated the whole Ulansuhai Lake area.After determining the treatment scope of Ulansuhai Lake,the preliminary estimate was about 45.75km~2,and the amount of organic pollution was about22.56 million tons,which can by treated by in-situ remediation method.Phragmites and potamogeton pectinatus can effectively absorb and control the release of nutrients from sediments.The results showed that the purification effect of phragmites groups was higher than that of potamogeton pectinatus groups.Phragmites groups had the best purification effect on mild eutrophication water body,and high-density phragmites groups had the best purification effect on water quality.It was suggested that outburst and submerged plants be planted in sediments with high organic pollution,and most of the nutrients can be taken out by harvesting the above-ground parts of outburst plants at maturity stage,so as to prevent the secondary pollution of lakes caused by decay of sediment bottom after plant death and slow down the trend of lake bottom elevation.