| Liao river,one of the seven major rivers in China,originates from Guangtou Mountain in Pingquan county,Hebei province and it flows through four provinces including Hebei,Inner Mongolia,Jilin and Liaoning(autonomous regions),totaling 1345 km in length.As the largest river in the southern part of Northeast China,Liao infuses through the Bo sea,with its basin area being 21.9×104 km,and Hun river,Liao river,west Liao river,east Liao river and Zhao Sutai river,etc.as its main tributaries.This paper takes parts of Liao river within Jilin Province as the main focus,including East Liao river,Zhao Sutai river and its tributaries Tiaozi river,which not only provide valuable water resources for the area they cover,but also receive local sewage from daily life,agriculture and industries.Thus,improving the river basin water condition and alleviating the agricultural non-point source pollution is the key problem to be solved in this heaviest-polluted river within Northeast China.Supported by pilot projects ―Liao river basin water pollution comprehensive treatment technology integration and demonstration‖ under the major national scientific and technological project,―water pollution control and governance‖hosted by my mentor,this study is based on the existing research results of our research group,combining with field sample collection,field test simulation and numerical model simulation.It carries out a systematic research on the basin soil water conservation and riparian buffer retention capacity,aiming to offer theoretical basis for improving riparian buffer rtention capacity,controlling agricultural non-point source pollution and easing the basin water pollution problems.The main conclusions of this paper are as follows:(1)The application of Arcgis10 in researching the spatial distribution characteristics of the river basin soil physical properties.On the two sides of the river and areas around its reservoirs,the spatial distribution of bulk density and total porosity takes a sharp contrast,with the bulk density being low.By contrast,farmland soil exhibits high bulk density value yet low total porosity value,indicating inferior soil moisture absorption and poor transporting capacity due to the frequent human activities;with regard to forest soil,the bulk density value is low and total porosity is high,indicating that the soil physical properties are greatly influenced by the forest tree species.(2)Study on water conservation capacity and spatial distribution characteristics of TN,TP based on geographic statistical methods.The research results show that the spatial distribution of soil water capacity when saturated exhibits a downward trend as it goes from the central to southeast areas;spatial distribution of effective water capacity shows a downward trend from southeastern areas to the northwest.Spatial distribution of soil total nitrogen and total phosphorus are consistent,all showing the anisotropic spatial heterogeneity and longitudinal gradient change trend from southeast to northwest.(3)The rainfall runoff experiment results show that the riparian buffer can intercept nitrogen and phosphorus,with the width of the buffer being one of the factors that affect its ability to intercept.On the other hand,water capacity and permeability obstruct its ability to intercept.(4)The application of finite element simulation to establish riparian buffer pollutant interception model and illustrate on the soil migration pattern of nitrogen and phosphorus in the buffer from a micro-scale perspective.The results further verify the interceptive effects that soil in the buffer exerts on nitrogen and phosphorus.The great precision of HYDRUS2D/3D simulation model can be properly applied in studying the nitrogen and phosphorous transport pattern in the buffer strips.(5)Suggestions regarding the proper construction of the riparian buffer are proposed based on the research results.Riparian buffers in 15-60 m width are best suited in low hilly land;5-20 m wide in plains. |
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