The Study On The Effect Of Vegetation Buffer Zone About N And P Pollution In Liao River Protection Zone

In the middle of 1990 s, with the construction of the northeast old industrial base and the rapid development of economy, the water pollution in Liao River Basin is aggravating.The main source of pollution is nitrogen and phosphorus from the agricultural non-point source pollution. So far, the construction of riparian buffer zone is one of the most economic and effective measures for controlling agricultural non-point source pollution. The domestic and foreign scholars have done a lot of researches about it, but for the northern region, especially in Liao River Basin, there are few reports about the riparian buffer zones of vegetation pattern and the effective width. The study of the best combination of the zone vegetation pattern, the reasonable and effective removal of width can provide theoretical basis for China to treat water pollution. It can also set up a solid theoretical foundation for the subsequent recovery of riparian buffer construction and provide theoretical guidance for building healthy riparian buffer zones.This study takes the middle and upper reaches of the Liao River Basin, Tieling section, as an example: firstly,the paper analyzes of the present situation and problems of riparian zone of Liao River reserve; secondly, the paper selects suitable herbaceous vegetation. Through laboratory hydroponic experiment research, the papercomparatively analyzesplant’s ability of removing nitrogen and phosphorus nutrition elements to determine the best riparian buffer zone plants; finally, the paper builds six different vegetation patterns of artificial riparian buffer zone according to the test site terrain, which canbe tested in the form of rainfall simulation. Bycomparatively analyzing the removal rate of different vegetation patternsand width of vegetation buffer in agricultural non-point source pollution, the paper concludes that :(1) The rate of the natural vegetation cover of Liao River has reached over 80%, but the species of vegetation are single. The mainly species are plant community and over 90%of them are herbaceous plants.(2) Based on the field survey, literature review and the guidance of plant experts, four herbaceous plants(coronilla varia, sweet clover, ryegrass and alfalfa) are selected into the hydroponic experiment. The result shows that it is the sweet clover that has the highest removal rate of nitrogen and phosphorus. The average removal rate of TN and TP are69.73% and 51.85%, respectively.(3) Different vegetation patterns have different effect on removing various forms of nitrogen and phosphor in the polluted water.The removal rate of nitrogen and phosphorus for shrub + grass vegetation model is significantly higher than that of single herb vegetation planting pattern. The average removal rates of TN、NH4+- N and TP for salix+ sweet clover buffer strip and single sweet clover buffer strip are 65.71%、67.85%、38.70% and 35.36%、41.19%、24.64%, respectively;(4) In the same vegetation pattern,the removal rate of nitrogen and phosphorus in the soil is significantly higher than that in the surface runoff. The average removal rates of TN,NH4+-N and TP in surface runoff and soil solution for salix + melilotic buffer strip are58.2%、40%、32% and 71.3%、66.4%、40%, respectively, with an increase of 18.4%、66% and 25%;(5) The removal rate of nitrogen and phosphorus increases first, then decreases and increases again with the increase of the riparian buffer zone width. When the width of the buffer zone is between 7-10 m, the removal rate is the lowest. However, the removal rate of nitrogen and phosphorus becomes the highest when the width reaches 13m;(6) In the six vegetation patterns of riparian buffer strips, the removal rate of nitrogen and phosphorus for salix + sweet clover buffer strip is the highest and the removal rate of ryegrass vegetation buffer strip is the lowest. The sequence of removal capacity of nitrogenand phosphorus for six vegetation patterns of riparian buffer strips are salix + sweet clover > salix + Artemisia genus weeds > sweet clover > artemisia weeds > salix +ryegrass > ryegrass.