Environmental Impact Assessment Of Nitrogen Pollution In Soil Of Aerated Zone On Groundwater In Xiong’an New Area

Xiong’an New District,as the leading city of the National Green City Development and Construction Demonstration,groundwater conservation will be an important part of the ecological civilization construction of the new district.In this study,the typical soil and groundwater in the aeration zone of Xiong’an New District were investigated,the “three nitrogens” was taken as the main evaluation factor.By analyzing the distribution characteristics of the "three nitrogens" concentration in the vertical section of the aeration zone and its enrichment depth,A preliminary evaluation of soil nitrate nitrogen pollution was given by using Hazen probability curve method and single factor evaluation method.the conclusion is as follows: Soil pollution is dominated by nitrate nitrogen,and the enrichment is above 10 m in profile,and 46.4% of soil pollution shows moderate pollution.Based on the vertical distribution characteristics of nitrogen,oxygen and oxygen isotopes and hydrogen and oxygen isotopes in soil,the vertical migration of nitrogen in the aeration zone and the possible migration depth were analyzed.The possibility of nitrogen in the soil entering the groundwater was discussed.According to the status of nitrogen pollution in aeration zone and groundwater,the relationship between groundwater and soil nitrogen pollution was established by nitrogen and oxygen isotope tracing method.The contribution of nitrate nitrogen in groundwater to the upper soil was obtained.Nitrogen pollutants can migrate vertically to groundwater.On this basis,the soil bulk density,water content porosity and groundwater dilution coefficient were used as evaluation factors.The calculation method of soil nitrogen concentration pollution limit for groundwater quality was established by the principle of three-phase equilibrium coupled groundwater dilution model,and the following conclusions were obtained: The concentration of nitrate nitrogen in the soil exceeded the standard,the proportion of pollution risk to high risk is 62.5%;The rate of nitrite nitrogen and ammonia nitrogen is lower,the number of samples with a maximum nitrogen concentration lower than the standard limit accounted for 97.5% and 77.5% of the total sample,respectively.Parameter sensitivity analysis showed that soil bulk density and water content porosity were the main influencing factors of risk assessment.