Distribution Characteristics Of Soil Nitrogen In Aeration Zone Along Dasha River

Nitrogen pollution has become a worldwide environmental problem.Nitrogen pollution is common in surface water and groundwater at home and abroad,which poses a serious threat to drinking water sources.This paper starts a study on the Dasha River section near Lingquan Lake at the head of the New River and the Jiaozuo Section of the Middle Route of South-toNorth Water Transfer.Through field surveys,site sampling,long-term observations,and laboratory tests,The nitrogen content and form on the profile of the Dashahe aeration zone are studied.Analyze the spatial distribution characteristics of nitrogen in the vertical and horizontal directions along the aeration zone along the river,and discuss its influencing factors and conversion mechanism.The results showd that ammonia nitrogen and nitrate nitrogen were the main nitrogen in the soil extracts of the aeration zone in the study area.The average contents of the two are3.481mg/kg and 4.938mg/kg,respectively.The content of nitrite nitrogen is the least.In different forms of nitrogen,the coefficient of variation of nitrate nitrogen is generally larger than that of ammonia nitrogen.In the same profile,the vertical distribution rule of different forms of nitrogen is different: the content of ammonia nitrogen decreases first and then increases with the increase of soil depth in the vertical direction.The content of nitrate nitrogen is lower in the surface layer of aeration zone and near the water surface,and higher in the middle;the vertical distribution of nitrite nitrogen has no obvious regularity.The distribution of nitrogen in the lateral space of aeration zone also has certain regularity.The content of ammonia nitrogen in vadose zone decreased with the increase of distance from river channel.The horizontal distribution of nitrate nitrogen in vadose zone is different with the increase of vadose zone depth,which can be divided into surface soil,middle soil and deep soil.As a whole,the content of nitrate nitrogen in vadose zone increases first and then decreases with the increase of distance from river channel.As the content of total nitrogen is affected by the content of ammonia nitrogen and nitrate nitrogen in the aeration zone,the change of total nitrogen with the increase of distance is not obvious.According to the horizontal section,except for the middle layer(0.6-0.8m),the content of nitrite in other layers is higher at the nearest(10m)and farthest(200m)from the river channel,and lower at the middle point.Through correlation analysis and principal component analysis,it is found that the distribution of nitrogen in aeration zone profile is closely related to the physical and chemical properties of soil.The main influencing factors of nitrogen form were different.The main factors affecting the distribution of ammonia nitrogen are water content,p H value and Eh value.Among them,water content,p H value and ammonia nitrogen content are positive,while Eh and ammonia nitrogen are negative.The main factors affecting the content of nitrate nitrogen are eh value and water-soluble salt,both of which have positive effects on the content of nitrate nitrogen.