Study On The Control Effect Of Pollution Resistance Of Typical Wetland Pond System In Danjiangkou Reservoir Area

Danjiangkou Reservoir is the water source of the middle line of the South-to-North Water Transfer Project.During the“Eleventh Five-Year Plan”to the“Thirteenth Five-Year Plan”period,the state implemented the third-stage pollution prevention and control plan in the Danjiangkou Reservoir Area,and the point source was basically controlled.With the gradual treatment of point source pollution,non-point source pollution control has gradually become the key to the water quality guarantee of Danjiangkou Reservoir.This paper selects three natural wetland pond systems of the natural,semi-natural and artificial types in the Danjiangkou reservoir area.Through the field monitoring analysis and indoor simulation test methods,the pollution control effects of different types of wetland ponds in the Danjiangkou reservoir area are studied.By using Duncan single factor analysis method,the control effect of natural and semi-natural wetland pond system on surface source pollution in Danjiangkou reservoir area is analyzed from time and space.From the perspective of load balance,the control characteristics of surface source of constructed wetland pond system are studied.The internal control characteristics of the system,the change of the control characteristics with time,the relationship between the control characteristics and the pollution purification effect,etc.,provide a scientific basis for the effect of the wetland pond system on the surface source control.The main findings are as follows:?1?The overall control effect of the natural wetland pond system represented by the Xiaohe small watershed is not significant.From the spatial point of view,the average value of total nitrogen and total phosphorus in Wetland Pond No.1 monitoring point is the highest;the average value of total nitrogen concentration in Wetland Pond No.2monitoring point is the smallest,and the mean value of ammonia nitrogen concentration is the highest;in the natural ditches monitoring point,compared with other ditch monitoring points The average concentration of total phosphorus and permanganate index in the natural ditches No.1 monitoring point is higher;in all monitoring points,the average value of total phosphorus concentration in natural wetlands is the lowest,0.03 mg/L;the average concentration of each pollutant in the basin is not at the highest status.?2?The semi-natural wetland pond system represented by Zhanggou small watershed has a good removal effect on some indicators.In the wetland pond system,the average nitrogen concentration of the No.2 monitoring site was the highest,2.85 mg/L,and the mean values of ammonia nitrogen and permanganate index were the lowest,0.32 mg/L and 2.89 mg/L,respectively.The average phosphorus concentration was the same.The direction of water flow shows a decreasing trend,that is,Wetland Pond No.1 acts as a“source”in total nitrogen removal,and acts as a“sink”in ammonia nitrogen and permanganate index removal;Wetland Pond No.2 in terms of total nitrogen removal It has the function of“sink”and acts as a“source”for the removal of ammonia nitrogen and permanganate index;the wetland pond system has a good removal effect on phosphorus.The mean values of total nitrogen,ammonia nitrogen and permanganate index in the deep pool area of the river channel are higher than the average concentration of pollutants in other monitoring points in the river section.The average value of total phosphorus concentration in the deep pool area is lower than the average concentration of pollutants in some monitoring points.?3?The artificial wetland pond system represented by the Yujiawan small watershed has obvious effect on the prevention and control of pollution runoff purification.The average removal rate of total nitrogen and ammonia nitrogen in the wetland pond system can exceed 80%,the overall removal rate of total phosphorus is about 80%,and the removal rate of permanganate index is close to 40%.The wetland pond system has a good removal effect on pig farm wastewater.The effluent concentration of total nitrogen and ammonia nitrogen is basically lower than 2.5 mg/L,which is better than the first-class A emission limit of comprehensive wastewater discharge standard?GB18918-2002?;The phosphorus emission concentration is lower than 1 mg/L,reaching the first-class B emission limit of the comprehensive wastewater discharge standard;the permanganate index export concentration reaches the Class III standard of surface water environmental quality standard.?4?Factors such as the area of the constructed wetland pond,the type of plant,and the concentration of pollutants at the inlet will cause the amount of pollutants adsorbed by the sediment to be different,so that the sediment release characteristics of different constructed wetland ponds are different.The average nitrogen flux of the No.1 pond sediment was the largest,which was 343.37 mg·?m²·d?^-1.The average nitrogen flux of the bottom mud of No.4 pond was the highest,which was 12.60 mg·?m²·d?^-1;The release flux of total phosphorus in the mud of No.1 pond was the largest,which was 29.71mg·?m²·d?^-1.The maximum release flux of permanganate index in the No.3 pond sediment was the largest,which was 168.16 mg·?m²·d?^-1 The absorption of pollutants in the mud of the No.1 and No.2 ponds is the dominant factor,and the absorption of the plants in the No.3 and No.4 ponds is the main factor for the removal of pollutants.