Analysis And Evaluation Of Available Nitrogen Content In Soil Of Shenzhen City

Soil is a basic component of environment and it is one of the most important natural resources.In soils N losses not only impact groundwater,but also cause non-point source pollution and eutrophication.This paper takes the water source protection area,river estuary,coastal area sediments,vegetable planting soil and golf course soil in Shenzhen as the research object,and analyzes the distribution of available nitrogen content in different soil types.We are using the principle of statistics to establish a semivariogram function model,and carry out ordinary Kriging interpolation analysis and calculation.The main conclusions are as follows:1.In the research area,there are average concentration of soil available nitrogen in water sources,river estuaries,coastal area sediments,vegetable planting soil and golf courses which contents are 59.43 mg/kg,119.96 mg/kg,53.24 mg/kg,54.10mg/kg,45.15 mg/kg.The highest and lowest average content of available nitrogen is found at river estuaries and golf courses respectively.The soil available nitrogen coefficient of variation is a medium intensity variation.Statistical results are normally distributed.The average ammonia nitrogen content is 6.42 mg/kg,36.51 mg/kg,2.23mg/kg,1.68 mg/kg,2.04 mg/kg,respectively.The highest and lowest average content of available nitrogen is found at river estuaries and vegetable planting soil respectively.The results show that the ammonia nitrogen content is relatively stable.The coefficient of variation of ammonia nitrogen is the same as the intensity of variation of available nitrogen.Statistical results are normally distributed.The average nitrate nitrogen content is 1.72 mg/kg,5.26 mg/kg,0.64 mg/kg,8.31 mg/kg,and 0.95 mg/kg,respectively.The highest and lowest average content of nitrate nitrogen is found at vegetable planting soil and coastal area sediments respectively.The statistical results show that the coefficient of variation of nitrate in river estuary and water source soil is greater than 1,which is a super-intensity variation,indicating that the nitrate nitrogen content of these two places is greatly affected by the external environment.The analysis results show that the content of nitrite nitrogen in soil accounts for the lowest proportion of available nitrogen,it's about 5%.This indicates that the nitrate content in soil is little in available nitrogen.2.The distribution of soil nitrogen in the near surface water of the survey area indicates that the soil nitrogen content in the river estuary is greatly affected by industrial pollution and human activities,and the soil in the secondary protected area of the estuarine soil and water source contributes to surface water pollution.The coastal area sediment has little contribution to the nitrogen pollution of the surrounding seawater,and the seawater nitrogen pollution mainly comes from pollutant discharge.The distribution of soil nitrogen in the ecological planting area of the survey indicates that agricultural non-point source pollution plays an important role in the pollution of surface water bodies.The most important pollution factor for the environment is nitrate nitrogen.We must strengthen the scientific management of vegetable plots and rationally apply fertilizer to prevent nitrate nitrogen in the soil from causing eutrophication in the surrounding water bodies.At present,the risk of non-point source pollution from Shenzhen golf courses is not enough to threaten the surface water quality of Shenzhen.The impacts of the soils in the survey area on the nitrogen content of the water environment are as follows:vegetable planting soil,river estuaries,water sources,golf courses,coastal area sediments.3.The semi-variance theoretical simulations of available nitrogen,ammonia nitrogen and nitrate nitrogen in soil showed that the available nitrogen accorded with the Gaussian model,the ammonia nitrogen accorded with the index model,and the nitrate nitrogen accorded with the spherical model.The spatial distribution of soil N content is simulated by ordinary Kriging interpolation unbiased valuation method.Available nitrogen is characterized by point distribution.NH₄⁺-N is characterized by zonal distribution which is decreasing from north to south.Ammonia nitrogen content in the northwest and south is higher than other places.NO₃^--N is charactrerized by zonal and island-shaped distribution,which is concentrated in the middle and north,and showing a decreasing trend from south to north.Soil nitrate nitrogen has a certain impact on the nitrate content in surface water.The main sources of pollution are industrial activities and human activities.