Distribution Of Nitrogen In The Soil Profiles Around The Wenyu River Unsaturated Zone

Nitrogen pollution has become a worldwide environmental problem. Nitrate is considered the most ubiquitous contaminant of groundwater in the world and often poses a serious threat to the quality of public drinking water supplies. In recent years the pollution of groundwater with nitrate in Beijing area has been further aggravated. Based on the previously study on the distribution of ammonium and nitrate in groundwater,aiming at the seriously contaminated areas along Wenyu River, a series of fine profiles in unsaturated zone have been conducted. The vertical distribution character of nitrogen in unsaturated zone profiles have been studied in different areas, which are contaminated with different concentrations of ammonia in groundwater. Meanwhile, impact factors and mechanism, which is important to influence the dis-tribution, form and content of nitrogen, are discussed through comparative analysis and principal components analysis.The soil sample collected from unsaturated zone were analyzed. The results showed that: ammonium-nitrogen and nitrate-nitrogen are the main nitrogen forms in the vadose zone, whereas the content of nitrite-nitrogen is the lowest. The average concentration of ammonium-nitrogen and nitrate-nitrogen are 5.76mg/kg and 5.52mg/kg, respectively. The variance coefficient of nitrate-nitrogen is the greatest, and that of nitrite-nitrogen is the smallest, ammonium-nitrogen is midterm. And ni-trate-nitrogen has a stronger variability. Among the five profiles, profile 4# possesses the highest nitrogen content while profile 2# shows the lowest one. The vertical dis-tribution of nitrogen in one profile is different according to different forms of nitrogen. The concentration of ammonium-nitrogen is increase with the increase of depth. The concentration of nitrate-nitrogen both in the upper profile and the lower profile are smaller than the middle profile, making the curve like a“peak model”; and the con-centration, below the water table, become decrease with the increase of depth. The distribution of nitrite-nitrogen is unconspicuous. And the distribution of total nitrogen in the profile is controlled by the distribution of ammonium-nitrogen and ni-trate-nitrogen. The results of the comparative analysis indict(indicate) that the distribution of ni-trogen in the profile(s) have a good consistency(correlation) with the lithology, Eh and groundwater table in the unsaturated zone. In order to make a further understand of the factors that are important to control the distribution of nitrogen, principal com-ponents analysis is used. Both the results of principal components analysis and related analysis show that: the main factor is various based on different snitrogen forms. The lithology, Eh and water content in the profile are important to the distribution of am-monium-nitrogen. Both the content of clay and water moisture have a promoting effect on the concentration of ammonium-nitrogen.While Eh value has an inversely relationship with ammonium-nitrogen. That is, the concentration of ammo-nium-nitrogen will increase with the decrease of Eh value. With regard to ni-trate-nitrogen, the main factors affecting its distribution are lithology and Eh. Both the content of clay and Eh has a positive effect on the concentration of nitrate-nitrogen.