The Study Of Biological Denitrification In Dongping Lake Water

Dongping Lake is not only the final water-transferring lake of the east line of the"South-to-North Water Deliver project",also bear the important function of the water source of West-to-East Water Deliver project in shandong province,special geographic location makes the Dongping lake plays a very important role in supply water,aquaculture,tourism,flood control,maintain the ecological balance,and social stability,so the water environment is very important to the intake area.In this paper,the denitrification ability of Dongping Lake was discussed by analyzed the water environment and studied the denitrification rate and the potential of summer denitrification under different vegetation/utilization methods.Based on the investigation of the dominant species of Phragmites communis and Potamogeton crispus,the plant denitrification ability of Dongping Lake was obtained.The factors of affect the denitrification rate of Dongping Lake were studied by factor control experiment.And finally,systematically analyzed the Potamogeton crispus denitrification by simulation.Based on the research above,the main conclusions as following:（1）The average of TP in overlying water was 0.041±0.032 mg·L^-1,and NH₃ was1.17±0.24 mg·L^-1,The variation range of NH₄⁺in surface sediments was 10.39²40.00mg·kg^-1,The variation range of NO₃^-was 0.01⁵6.14 mg·kg^-1,and the variation range of organic matter was 3.23⁹0.91 g·kg^-1,All the indicators showed higher in summer.Both NH₃ and TP in each region overlying water have samples exceeded the typeⅢstandard values of GB 3838-2002 National Environmental Quality for Surface Water,and the content of NH₃,NO₃^-and NO₂^-in the mixed zone was significantly higher.The NH₄⁺and organic matter was highest and NO₃^-was the lowest in Phragmites communis area of the surface sediments.The seasonal variation of the physical and chemical indexes in different regional columnar sediments was inconsistent,in the vertical direction,In addition to the NH₄⁺and organic matter in the aquaculture area is mainly concentrated in the surface layer0-1 cm and NO₃^-is mainly concentrated in 3-4 cm,and there is no significant difference between the other three regions.（2）The results showed that the denitrification rates in the surface sediments of Dongping Lake were between 1.01μmol·m^-2·h^-1 to 29.48μmol·m^-2·h^-1 and it mainly happens in winter.The region of denitrification rates under Phragmites communis area,aquatic culture area,Potamogeton crispus area and macrophyte mixed area respectively was 1.21²9.48,1.19²1.38,1.33¹9.81 and 1.01⁸.59μmol·m^-2·h^-1,The denitrification of columnar sediments mainly occurred at 0-1 cm in aquatic culture area,while the other regions mainly occurred at 2-3 cm,but there was no significant difference.（3）Based on denitrification impact factor analysis,the seasonal and the regional of different vegetation types and utilization patterns play the important role for the denitrification rate in Dongping Lake.The factor control experiment showed that the influence of different factors on denitrification is NO₃^-concentration>temperature>the TOC concentration,denitrification rate and NO₃^-concentration presented a very significant positive correlation,and on the whole,there also have a negative correlation between denitrification rate and temperature,there is no significant relationship between denitrification rate and TOC concentration.（4）Through the indoor simulation experiment of Potamogeton crispus,the results showed that the effect of different biomass on the overlying water was significant,and the effect on sediment was relatively small.The denitrification rate range is0.20±0.002².89±0.65μmol·m^-2·h^-1,and the denitrification rate was no significant differences between three kinds of biomass,it was mainly influenced by the aquatic environment and the denitrification mainly by water diffusion denitrification.（5）According to the study of Dongping lake biological denitrification,the total amount of nitrogen removal was 184.63 t·a^-1,The region of nitrogen removal under Phragmites communis area,aquatic culture area,Potamogeton crispus area and macrophyte mixed area respectively was 31.09,22.56,126.00 and 4.98 t·a^-1,seasonal variation performance for highest nitrogen removal in winter and low in spring.Under the conditions of sufficient nitrate and organic carbon source,the potential denitrification in summer was 1711.11μmol·m^-2·h^-1,the potential denitrification rates in the Phragmites communis area,aquatic culture area,Potamogeton crispus area and macrophyte mixed areanear the shore were 1711.11,1179.44,1023.61 and 1334.19μmol·m^-2·h^-1.According to the plant nitrogen removal study,the Phragmites communis and Potamogeton crispus amount of nitrogen were about 33.48 t and 50.03 t.There was a great significance for control the nitrogen concentration,reduct the nitrogen loadcuts and improving the quality of environment through denitrification and salvage plants.