Study On The Impact Of DO On The Release Of Nitrogen And Phosphorus From Sediment In Eutrophic Water

When the water body has high concentration of nitrogen and phosphorus, it will cause a large growth of cyanobacteria. Under this condition, the water will become eutrophication. After the exogenous nitrogen and phosphorus have been effectively controlled, the nitrogen and phosphorus in sediment will become the major pathway leading to eutrophication. The release of nitrogen and phosphorus in sediment is affected by a variety of external factors, and the dissolved oxygen (DO) is one of the most important factors. Therefore, this paper will set three different level of dissolved oxygen:highly dissolved oxygen(DO>7.0mg/L)、anaerobic (DO<1mg/L) and low dissolved oxygen (2.0mg/L<DO<4.0mg/L))in order to explore the law of the impact of DO on the release of nitrogen and phosphorus from sediment. At the same time we also study the affect of various degree of nutrient in the water body on the release of nitrogen and phosphorus under less dissolved oxygen level. Meanwhile we will use GM (1,1) model to predict the change of total nitrogen and total phosphorus in water body.According to the experiment, we found the dissolved oxygen was the most important factor to the nitrogen and phosphorus release from sediment to overlying water. At the highly dissolved oxygen level, the NO3--N was the main form release from sediment. However the NH4+-N was more easily release from sediment when the dissolved oxygen was less than1mg/L. And the best condition to remove nitrogen in water body and sediment was under highly dissolved oxygen. The law of nitrogen release from sediment would not change after adding organic carbon. Only when the dissolved oxygen was between2mg/L to4mg/L will be benefit for the remove of nitrogen in water body. Also phosphorus in sediment would more easily release when the water body was anaerobic. While in the rest of the dissolved oxygen conditions would inhibit the phosphorus release from the sediment.Nutrient degree also affected the nitrogen and phosphorus release from sediment. When the dissolved oxygen water body was about2.0mg/L to4.0mg/L, it had no affect on the law of nitrogen and phosphorus release. The nitrogen release would be promoted by the low nitrogen degree in water body; otherwise it would prevent the nitrogen release from sediment. Also with the increasing COD concentration would be propitious to the NH4+-N and NO3--N release from sediment, but it would inhibit the removal the total nitrogen in sediment. The adsorption of phosphorus would be promoted when phosphorus concentration was in highly level.The model of GM (1,1) was capable of predicting the change of total nitrogen in water body; however, the total phosphorus in water body could not be predicted.