The Characteristics Of Internal Pollutants In Sediment And The Research Of In-situ Controlling In Nanfei River Demonstration, China

The sediment of Nanfeihe River records the history of water pollution, authropogenic influence and environmental transition nearby, due to its tight interaction and connection with water body quality of Nanfeihe River. For controlling endogenous load and improving ecological system condition of Nanfeihe River, it has important theoretical and practical significance to do a research on current status and dynamic change of sediment pollution of Nanfeihe River. Under the state water pollution control and treatment of major science and technology topics relying (issue:2011ZX07303-002), we did plenty of indoor experimental analysis, it systematically focus on the nutrients of engineering demonstration sediment, the contaminative characteristics of heavy metal, the risk assessment of environment, the nutrients releasing rule of sediment-overlying water interface, the result of Nanfeihe River sediment nutrients releasing under the circumstance of in-situ control technology:(1) From the engineering demonstration to take 10 representative sampling point, the content range of nitrogen, phosphorus and organic matter were 253.83mg/kg-1235.73mg/kg,131.34mg/kg-1068.75mg/kg and 1.49%-6.83%, with high content of nitrogen and phosphorus in the surface sediment. According to the evaluation results of organic nitrogen and organic index, there was a certain degree of nitrogen pollution and organic pollution in demonstration period. The content range of heavy metals Pb, Zn, Cr in surface sediment of demonstration period were 21.6-152.9mg/kg,36.7-1529mg/kg and 33.6-132.6mg/kg. Through the evaluation results of geoaccumulation index and potential ecological risk coefficient method, the pollution degree of heavy metals in sediment was Zn> Pb> Cr; the content of Zn had exceeded the safety value in each sampling point, and there was more serious Zn pollution in the sampling points of P8, P9 and P10; the pollution of Pb mainly concentrated in the downstream area; there was a lesser degree of Cr pollution which mainly distributed in the sampling points of P9 and P10.(2) Results of nutrients releasing rule at sediment-overlying water interface illustrates that:a. As temperature of water environment grows, it influences much more to nutrients releasing at sediment-overlying water interface. When the temperature reaches 25 ℃ from 5 ℃, concentration of P shows a gently downward trend after the first rise and concentration of N states a fast increasing trend from a slow one in overlying water, along with concentration of COD increased by 1.64-fold; b. Whilst water environmental PH is 7, N、 P and COD releasing reaches minimum at sediment-overlying water interface, and the releasing level grows whatever the PH of water becomes upper or lower; c. Distribution influences nutrients releasing at sediment-overlying water interface in a greater effect When the distribution to it is strong enough, sediment in water will be floating again, which leads increasing concentration of N, P and COD in overlying water.(3) By adding some physicochemical coagulants, the experiment controlled by in-situ control method based on exploring sediment nutrients releasing shows that:when the amount of coagulant reaches 800mg/L, the controlling effect aimed on sediment nutrients releasing do the best.