Study and Application of Layered Sediment Nutrient Release for a Waterfront Body

The spatial characters of accumulated sediment,pollutant content distribution in sediment in Neijiang were systematically analyzed.By conducting the layered sediment nutrient release experiment,the relationship between sedimentary pollutant release intensity and water velocity was induced for each divided area in Neijiang.A 2-D unsteady flow-water quality numerical model which contained the internal pollutant release was established and the post environmental impact of the dredging program in Neijiang was quantificationally estimated.It was found that the sediment deposition and pollutant content in sediment in Neijiang were asymmetrically distributed and the thickness and pollutant content of the deposited sediment in the south area of Neijiang were higher than that in other areas. Generally the pollutant content in sediment decreased from the surface layer to the bottom layer,and the release intensity of TN,TP,COD of the middle layer was averagely decreased by 40.8%,32.1%,and 28.3% than that of the surface layer respectively.After the dredging program the intensity of internal pollutant release in Neijiang was obviously weakened and the total amount of internal pollutant release during the tidal cycles in flood and dry season were reduced by 26.3% and 22.3% respectively than that under the present condition.