Adsorption And Release Of Heavy Metals In Sediments Of Poyang Lake Under Different Hydrodynamic Forces

With the development of economy and society,heavy metal pollution has been widely studied by scholars at home and abroad due to its difficult biodegradation and typical "three causes".Once the pollutants such as heavy metals enter the ecological environment,they are easy to accumulate in sediments and organisms.The enrichment process mainly includes physical,chemical and biological factors.In this paper,the risk assessment of heavy metals was carried out in the surface sediments of five rivers of Poyang Lake and typical representative areas.The law of adsorption and release of heavy metals in sediments at the tail end of Ganjiang River of Poyang Lake was studied,which provided the basis for improving the water quality prediction model.The main contents and conclusions of this paper are as follows:(1)Based on the sampling and analysis of the sediments from the five rivers of Poyang Lake and typical representative areas,it is concluded that the average contents of four heavy metals in the study area exceed the background values of the sediment in the Poyang Lake Basin and the soil background values in China.Therefore,there is heavy metal pollution in the sediments of Poyang Lake basin to a certain extent,and the heavy metal pollution is CD > Cu > Zn > Pb.(2)The results show that the total potential ecological risk and ecological toxicity of heavy metals in the sediments of the five rivers of Poyang Lake and typical representative areas are low by using the geo accumulation index method and the potential ecological risk index method;and the heavy metal pollution in Poyang Lake Basin has significant difference in sample plots,among which Raohe River Estuary S7,Xinjiang River Estuary S5 and Ganjiang North Branch S1 have become the main heavy metal pollution areas.(3)The PES resuspension simulation device was used to study the adsorption of heavy metal Cu,and it was concluded that the sediments had a strong adsorption capacity for heavy metal Cu,the maximum adsorption capacity was 245.250mg/kg,and the balance of Cu on the sediments The amount of adsorption increases with the increase of shear stress.The correlation coefficients of Freundlich model fitting Cu are above 0.95,which can fit Cu well.(4)The adsorption of Cu on the sediment is mainly fast adsorption,and itsadsorption capacity accounts for more than 45.97% of the total adsorption capacity.Slow adsorption contributes little to the total adsorption process.According to the adsorption kinetic experiment,the functional relationship between the heavy metal Cu adsorption amount qt and C0,τ,t is obtained.When the shear stress and the initial concentration of heavy metal Cu are accurately known,the corresponding functional relationship can be substituted Predict the amount of Cu adsorbed in the sediment at different time periods.(5)The release process of Cu and CD was simulated by PES resuspension simulator.The results showed that the shear stress of pollutant release in sediment was proportional to that of Cu and Cd in overlying water in the order of high speed >medium speed > low speed.The higher the intensity,the higher the concentration.The maximum release of Cu and Cd in sediment was in the order of high speed > medium speed > low speed In other words,the greater the turbulence intensity,the greater the release.