| pond is an important type of water body in villages and towns in the northern plains,pond has an important impact on the environment of villages and towns.Non-point source pollution in villages and towns in the northern rural areas represented by the North Canal(Tianjin Section)are prominent,combined with the ideas of river basin management planning,we Conducted an investigation of village pond,as well as pond non-point source pollution control technologies.Provide technical support for the improvement of the water environment of the North Canal(Tianjin Section)Canal.In this study,through the analysis of the landscape pattern index of Wuqing District,the spatial distribution characteristics of pond and related patch types in the area are clarified.The pond are the main nodes of non-point source pollution.On this basis,through on-site investigation,sampling and analysis of the current water environment of typical villages and towns pond.According to the survey results,combined with the current status of technology and economy,an optimized experiment was conducted on the pond constructed wetland technology.The experiment determined the mix ratio of the composite filler and the residence time of the pond wetland.The QUAL2 K model was used to simulate the contribution of optimization measures such as pond and wetlands to the reduction of pollutants entering the North Canal.The main conclusions of the paper are as follows:(1)There are 14 types of plaques in the study area.The distribution structure of each type of plaques is relatively compact,the shape is relatively simple,and the shape of the canal is slightly complicated.The ratio of reservoir ponds to dry land is about 9:1,which is consistent with the distribution ratio of traditional ponds.Dry land,rural settlements and reservoir pits are the three main types of land use,and also the three types of plaques with significant edge effects.These types of plaques are more open and human activities are more frequent.And there is more material energy flow with the river channel and lake patches.Reservoir pits,canals and dry land patches have good spatial connectivity.(2)There are four main types of location relationship between pond and ditches in the study area.Based on this,six typical village and town pits closely related to the North Canal were selected to carry out water environment surveys.It was found that the worst months of water quality were November in winter and July in summer.One of the most representative pond is Dawang Village.The survey shows that the representative ponds have high plant diversity and singularity,have certain autotrophic ability,but are subject to human disturbance.The water quality fluctuates a lot and belongs to eutrophic water bodies.Peripheral runoff pollutant analysis shows that the pre-precipitation with SS as the object of removal can also remove COD,TP,NH3-N and other pollutants.(3)In the pond wetland optimization experiment,the results of the matrix filler adsorption experiment showed that the removal rates of TP,fly ash,steel slag,and anthracite coal were all high,the removal rates of COD were average,and the removal rates of NH3-N and TN were poor.Among them,fly ash will make the effluent more alkaline;while anthracite will make the effluent weakly acidic.After optimization experiments,fly ash,steel slag and anthracite were used in a ratio of 1:1:2.Rain test shows that SS removal rate of pond wetland is 72.3%,TN removal rate is about 42.49%,TP removal rate is about 43.64%,NH3-N removal rate is about 46.78%,COD removal rate is about 58.21%,SS removal rate is 74.5%,and p H meets Farmland irrigation water standards.(4)The simulation results of the QUAL2 K model on river improvement measures show that pond wetlands have a certain contribution to the reduction of river pollution load,and the removal effect of NH3-N is better than phosphate.Together with other improvement measures,the specific nitrification rate of the river can be increased to 0.2. |
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