Study On Release Law And Biological Stability Of Pollutants In Wetland Sediment

Sediment pollution has become the focus of water environment pollution prevention and control.Water pollution events in many areas are caused by sediment,and the problem of internal pollution has attracted the attention of many scholars.The concentration of pollutants in sediment is usually several times or even dozens of times higher than that in overlying water.Most of the studies on sediment in China are typical rivers and lakes,such as"three lakes"and"three rivers".Because the geographical location of each river and lake is different from its sedimentary environment,the sedimentary behavior has occurred.Even if the same research method is used to study the sediment of different waters,the results may be very different.Daqing Longfeng Wetland is the only place in Heilongjiang Province at present,there is little research on the urban wetlands of peat sediment such as Daqing Longfeng Wetland.Therefore,this paper takes the Longfeng Wetland sediment as the research object.The release law and surface characteristics of typical pollutants in sediment are studied,and the release of pollutants in natural state is simulated in order to find out the release law of pollutants at the interface between sediment and water.To explore the adsorption behavior of typical pollutants on the surface of sediment particles is of positive significance to the treatment of sediment in typical waters of northern China.Based on the analysis of the physical and chemical properties of the sediment and overlying water body of Longfeng wetland in Daqing,the causes of water pollution and the content of pollutants were found out in this study.The effects of different soil-water ratio,disturbance intensity and static time on the content of sediment pollutants were investigated,and the release of static and sediment suspended pollutants was compared by simulating natural water conditions.The adsorption capacity and kinetic behavior of nutrients in sediment were studied by traditional adsorption experiment,and the fractal characteristics of sediment particle surface were studied by covering method.Finally,the oxygen consumption characteristics and biological stability of black and smelly sediment were studied.The results show that the water body of Daqing Longfeng Wetland is inferior V,the sediment is rich in organic matter,the particle size is small,and it is easy to release pollutants into the overlying water.In the aspect of sediment pollutant extraction,when distilled water is used as leaching solution,the ratio of soil to water is small,the greater the oscillatory intensity is,the more pollutants are extracted,and the extract should be centrifuged in time.After six cycles of cleaning,the sediment can be cleaned.The discharge of pollutants from sediment under static condition is much smaller than that under dynamic resuspension,and the release amount of pollutants in 1 hour is tens or even hundreds of times as much as that in static condition for 1 day.With the increase of resuspension times,the particle size of sediment decreases and the viscosity decreases.The grain increased by 12.596%,the specific surface area increased to 2664.4 kg/m²,and the fractal dimension increased from 2.504 to 2.783.The fractal dimension was positively correlated with SSA and clay content.After cleaning,the maximum adsorption capacity of NH₃-N and SRP was 0.573 mg/g and 0.72 mg·g,respectively.the fitting degree of adsorption kinetics curve was higher than that of quasi-second order kinetic curve.The description of adsorption in fractal adsorption model is more microscopic than that in traditional adsorption model.The surface fractal dimension of sediment particles is 2.6887,and the average coordination number of one SRP molecule and particle surface active site is 0.86.The adsorption of SRP on sediment is irreversible.The oxygen consumption of sediment is a complex process.According to the sediment of Longfeng wetland,its oxygen consumption characteristics can be divided into strong reductive material oxygen consumption.There are five stages:reducing substance oxygen consumption,biochemical carbon oxygen consumption I,biochemical nitrogen oxygen consumption and biochemical carbon oxygen consumption.The sediment of 0.035m3consumes 20.584 mg dissolved oxygen for 36 hours.The pollutants in the disturbed sterilized sediment reached stable after 9 days of release,while the stability process of the unsterilized sediment was divided into first release and then degradation,and the concentration of pollutants was in dynamic balance.