Study On The Effects Of Sediment Elution On Overlying Water Environment And Sediment Nutrient Migration And Transformation

Endogenous pollution of sediments is one of the main causes of eutrophication in water bodies.Due to the complex and changeable generation and deposition processes of endogenous pollution of sediments,it brings great challenges to water pollution control.Nowadays,endogenous pollution has become a global phenomenon.environmental issue.In this study,the black and odorous sediment on the wetland surface and the original overlying water of the wetland were treated as the treatment objects.The effects of sediment elution on the overlying water environment and the migration and transformation of sediment nutrients in static and dynamic water conditions were discussed,in order to provide data support for the application of sediment elution engineering.The paper achieved the following results:（1）The sediment elution changed the morphology,composition and structure of the sediment,resulting in a significant decrease in the flow plastic sense of the sediment.Compared with the non-eluted group（C）,the proportion of sediment particle size in the eluted group（E）in the range of 63-2600μm increased by 26.7%on average,while the proportion of small particle size in the range of 4-63μm decreased by 48.9%on average.With the increase of the proportion of large particles in the sediment and the transfer of suspended particles,the bulk density of the sediment in the eluted group（E）increased by 9.01%on average compared with that in the non-eluted group（C）.At the same time,the water content and organic matter of the sediment decreased after elution.The analysis of sediment storage shows that the first elution has a great influence on sediment storage,and the influence degree decreases with the increase of elution times.（2）Sediment elution can obviously remove the turbidity and SS concentration of overlying water in still water state,resulting in an increase in the transparency of overlying water.In the elution group（E）,the turbidity of overlying water decreased by32.4%on average,and the transparency increased by 3.6%on average.The elution of sediment increases the times（time）of sediment-water-gas contact,and has obvious improvement effect on the anaerobic environment of water body.In the static water state,the average horizontal DO concentration of the non-elution group（C）is only 0.86 mg/L,while that of the elution group（E）is 3.3mg/L;Due to the recovery of DO concentration in water,the degradation effect of N and P pollutants is remarkable.Under the static state,the average concentration of N pollutants in the non-eluting group（overlying water+interstitial water）is 8.2mg/L,and that in the eluting group（E）is 4.13 mg/L,which is 49.6%lower than that in the unwashed group（C）.In static state,the average concentration of TP（overlying water+interstitial water）in non-eluting group（C）is 0.54mg/L,and that in eluting group（E）is 0.19mg/L,which is 64.8%lower than that in unwashed group（C）.Under the static state,Ammonia nitrogen and soluble TP in the sediments of the non-eluting group（C）are mainly released,while those of the eluting group（E）are mainly adsorbed.The analysis of greenhouse gas release fluxes in hydrostatic state showed that the average CH₄,CO₂,N₂O release fluxes of the non-eluting group（C）were 0.742,7.4,and 0.01mg/（m~2·h）,respectively,while the eluting group（E）The average release fluxes were 0.066,4.6,and 0.002mg/（m~2·h）,respectively,which were 91.1%,37.8%,and 80%lower than those of the non-eluted group,respective（3）The anti-disturbance ability of sediment was significantly improved by sediment elution,and the sediment resuspension was inhibited.In the elution group（E）,the turbidity of overlying water decreased by 59.2%on average,and the transparency increased by 14.1%on average.During the experiment period,the average DO concentration in the eluant group（C）was 0.98mg/L,and that in the eluant group（E）was 3.48mg/L,with an average increase of 255%.Under dynamic water condition,the average concentration of N pollutants in the eluant group（C）（overlying water+interstitial water）is 10.3mg/L,and that in the eluant group（E）is 6.1mg/L,which is 40.8%lower than that in the unwashed group（C）.Under dynamic water condition,the average concentration of TP in the eluant group（C）（overlying water+interstitial water）was 1.29 mg/L,and that in the eluant group（E）was 0.36mg/L,which was 69.8%lower than that in the unwashed group（C）.In the elution group（E）,the release amount and risk of ammonia nitrogen and soluble TP in bottom mud were greatly reduced under the moving water condition.The elution treatment was still effective in reducing the release flux of CH₄,CO₂,and N₂O in a dynamic water environment.The average CH₄,CO₂,and N₂O release in the non-eluting group（C）were 0.39,3.26 and 0.003mg/（m~2·h）,respectively,the release amount of the eluted group（E）decreased by 87.8%,20.6%,and 75.6%,respectively,compared with the non-eluted group（C）.By transferring suspended particles in sediment,sediment elution can effectively reduce the endogenous pollution,improve the transparency of water body,and promote the recovery of DO in water body,which is extremely beneficial to the improvement of anaerobic environment of water body and of great significance to the restoration of water ecological environment for the growth of submerged plants.Figure[43]table[13]reference[110]...