Assessment Of Vulnerability In Groundwater And Numerical Simulation Of Nitrogen Pollution In The Blown-sand Region Of The Northern Shaanxi Provience

As an important part of energy and chemical industry base in northern Shaanxi, the wind beach area in northern Shaanxi is the base which focused on the major component of the national investment and collectted the mining and deep processing the oil, coal, natural gas, and the chemical industry with them as the main raw material in the whole. How to protect the scarce groundwater become the priority, with the shortage of water resources been the bottleneck restricting the development of the area. This study was conducted to identify the situation of groundwater pollution in the study area, numerically simulate the major pollutants of the "three nitrogen" to predict the trend of its changes, as well as research vulnerability of the groundwater in the area, map the strong vulnerable areas, provide a reference for the government's functional departments in correlative development plans-making.Vulnerability of the groundwater and numerical simulation of the "three nitrogen" was studied systemicly with the aim of protect the groundwater resoure , the object of shawllow layer groundwater and the way of collectting data,field survey,sampling and indoor experimentation. The results and recognize form the research are summarized as following:1. In the 783 water samples, the main pollution is the ammonia, nitrous acid nitrogen and nitric acid nitrogen, which are sub-standard rate of 3 percent, 12.48 percent and 12.86 percent respectively. Comparatively, the ammonia pollution is light , heavy pollution is only a few scattered points, including the Baijie forestry centre, Qingyun hill, Earslin beach, Gangfang fossa. The serious nitrous acid nitrogen pollution are mainly located in Zhangjiawan around Yulin City, Caohaize, and Qingyun hill, less pollution are distributed in sand dunes covered hill and valley, and no pollution is in the marsh area in the sand. The serious nitric acid nitrogen pollution areas are mainly distributed in Mahe farms, Niujialiang farms, Baijie forestry centre and the old Joss House Bay in the town of Balasu and other places. Nitrate pollution is mainly in farming areas.2.With the adoption of the reformative DRAIC modle, the vulnerability of the the wind beach area in northern Shaanxi is comparatively strong. Thereinto, the 56 percent of the total study area is occupied by the highly strong vulnerable area, and the 6.7 percent is occupied by the strong vulnerable area.3.The laws that root absord water is consistent with the laws that root absord the "triple-nitrogen", but the amount of absorption is relatively small for crops root. Nitrogen absorption of wheat roots is mainly in the form of NH₄⁺, less in the form of nitrous acid nitrogen and nitric acid nitrogen When the nitrogen application rate is about 275.5 kg/hm2, the "triple-nitrogen" absorption of the root is about 224.5 kg/hm², the absorption rate is 81.6 percent, while about 18.4% of the residual nitrogen is in the soil. Part of it is adsorbed by soil and part of it migrate adown with water into groundwater.4. The rate of ammonia migration in the aeolian sand is about 10cm / a. The ammonia moved to 63cm blow surface after five years, and moved to 96cm after ten years. The nitrous acid nitrogen and nitric acid nitrogen migration is faster than ammonia, they moved to the water table 3 meters below surface in the sixth year and the following year respectively, and the flux of nitrous acid nitrogen and nitric acid nitrogen into the water table were 0.00104 mg / cm³ and 0.0025mg/cm³.5. The ten years forecast showed that the most shallow groundwater in the study areas is in the good considition. The main polluted area is around the Yulin city,Qiaojie village and the old Joss House Bay Village near to the town of Balasu. The trend of the pollution is not clear, except for some little change in the scope of nitrous acid nitrogen pollution and some new pollutted point in Erlintu town and riverbay village.