Loss Of Nitrogen And Phosphorus On Water Pollution And Its Prevention Measures In Greenland Of Xi'an

Urban green space is an significant part of the sponge city.The building of urban green land has not only beautified the city's apperance,but also it has improved people's quality of life.However,with the rapid development of urban green space,there have been a series of broblem,such as soil pollution of urban green space has caused water pollution.This paper taked urban green space of Xi'an city as the researching object.By analyzing five different types of urban green land,about the content of nitrogen and phosphorus in the soil,the content of nitrogen and phosphorus in urban green land soil and its effect on runoff were studied.Thus,using montmorillonite,illite,and kaolinite as water-retainong agents,an improved simulation experiment was conducted on the green soil to explore the water retention properties of different water retaining agents and to calucate the water retention capacity.The research rusults provided scientific theoretical basis and technical supporting for the healthy develppment of urban green space soil,protection of urban water and soil environment,and construction of a new type of sponge city,making the development of sponge city more sustainable.Through the research,obtained the following main results could be obtained:?1?The contents of nitrogen and phosphorus in different types of green space were different.The order of nitrogen and phosphorus from high to low is:the botanical>garden>isolation>wetland>campus green space.Among them,the nitrogen content respectively were0.2412g/kg,0.2069g/kg,0.1630g/kg,0.1625g/kg,0.1481g/kg,and the phosphorus content were0.2577g/kg,0.2565g/kg,0.1833g/kg,0.1742g/kg,0.1636g/kg;the soil nitrogen and phosphorus contents in the vertical niche Greenland were gress soil>shurb soil>treesoil.Amongthem,thenitrogencontentrespectivelywere2.221g/kg,2.111g/kg,and1.881g/kg;the different factors in the soil were correlation anslysied.The water content of soil was significantly correland with total nitrogen,nitrate nitrogen,andavailablephosphorus.Thecorrelationcoeffcientswere0.895,0.867,and0.791.Therefore,the soil moisture content directly affected the content of nitrogen and phosphorus conteent in camous green soil,nitrogen and phpsphorus pollution load of surface runoff,it could be find that there was significant correlation betweeen nitrogen and phosphorus in soil and them in surface runoff,indication that the content of nitrogen and phosphorus in soil directly determined nitrogen and phosphorus content on surface runoff.?2?The loss of niteogen and phosphorus in green soil were mainly caused by surface runoff and seepage.The excellent water quality of rainfall runoff around the five different type of green land was:campus greenland>wetland>wetland>isolation zone greenland>park>botanical garden;surface runoff formed by 3 rainfall,the surface runoff of botanical garden and park are polluted;2 water bodies before the surface runoff of wetland were affected.To the pollution,the surface runoff formed by the third rainfall was not polluted;the surface runoff quality of the 3 rainfall in the campus was not polluted;During the three runfalling processes,the pollution load of pollutants on the surface runoff of campus were that pollution lad of nitrogen respectively were 679.72mg,641.24mg,409.01mg,and pollution loads of phosphorus resperectly were33.27mg,27.40mg,24.14mg.?3?It was accorounding adsorption experiment of repeated water absorption experment,absorptionexperimentofnitrogenandphsophoruswith montmorillonite,illite,and kaolinite shown that the ablity to adsorb water,nitrogen and phsophorus were montorillnite>illite>kaolinite.The langmuir model and Freundlich model were used to fit the the adsorption capacity of three kinds of water retaining agents in different concentractions of nitrogen and phsophorus.The results showed that the adsorption characteristics of the water retaining agent nitrogen corresponded to Langmuir model,whlie the adsorption effect of the water retaining phsophorus was more consistent with the Freundlich model.?4?The adsoeption experiments of three water retain agents shows that montorillonite had the best effect of water retention,N,P retention.Therefore,montmorillonite leaching experiment was chosen as a water retention agent to put in soil column leaching experiment,to study the effect of different concentrations of montmorillonite on nitrogen and phosphorus absorption.With the same height and different water-retaining agent content in soil colimnd,the nitrogen and phosphorus retention effect were:0.4g/kg water retention agent>0.2g/kg water retention agent>no water retention agent;with the same water retention agent content and different heights in soil columns.The concentration of TN,TP,NH₃-N,and soluble phosphorus all decresed with increasing of soil column height,except NO₃-N.Through comprehensive analysis of the above studies,it was recommended to apply montmorillonite with a mass fraction of 0.4g/kg in the surface soil of urban green space in the city of Xi'an in order to achive better water fertilizer retention effects.