The Contribution Recognition Of Groundwater Nitrogen Pollution Source In Hun River Riparian Zone

Li Guan Pu water source area lies in Hun River riparian zone, Shenyang.Groundwater nitrogen pollution problems in this area are relatively serious. Thepollution sources mainly include the infiltration of top soil pollution sources, the riversupplement of Hun River and the recharge of upstream. In order to provide decisionsfor managers to carry out good pollution treatment, it is very important to identify thesources of groundwater nitrogen pollution, and calculate the contribution of pollutionsources. In this paper, we carried out partition portrayed for the vertical infiltration oftop soil nitrogen, using Hydrus-1D to get the water volume and nitrogenconcentration at the bottom of the unsaturated zone, which can represent the regionalresults by using simulation results of the points data, and used it as initial value toinput the aquifer model to combine the simulation in top soil, unsaturated zone andaquifer. After that, we used Visual Modflow to establish the nitrogen migration andtransformation numerical model in the aquifer, and received the content of nitrogen,which was put into groundwater from various pollution sources, and calculated thecontribution rate of groundwater nitrogen pollution sources by equilibrium formulas.The main conclusions are listed below.(1) The simulation of vertical infiltration of top soil pollution source stuggeststhat the concentrations of ammonia nitrogen at the bottom of the unsaturated zone aredifferent in the south and north part of the research area. The concentration ofammonia nitrogen in the north part is higher, which varies from0.008to0.112mg/L;The concentration in the south part is lower, which varies from0.002to0.017mg/L.As a whole, the concentrations of nitrate nitrogen in the research area are similar, theconcentration in the north part is a little higher than the south part, which varies from4.603to7.555mg/L.(2) The calculating results of water balance stuggests that the recharge of theunconfined aquifer is mainly from the vertical infiltration at the bottom of theunsaturated zone, and the average recharge amount is8033.3m3/d. Secondly it isfrom upstream, and the average recharge amount is4155.6m3/d. The recharge from Hun River to groundwater is large, and the average recharge amount is3144.4m3/d.But the recharge from Xi River is little, which could be negligible. Artificialextraction is the main discharge in the research area and the exploitation quantity is2300m3/d. These is water exchange in groundwater between the north and south partof the research area, which is recharged from south to north.(3) The calculating results of equilibrium contribution stuggests thatgroundwarer nitrogen pollution of the south and north part of the research area comesfrom different sources. Ammonia nitrogen in the south part is mainly from Hun River,and the contribution rate is61.79%. Nitrate nitrogen in the north part is mainly fromtop soil vertical infiltration, and the contribution rate is43.92%. As a whole, ammonianitrogen of the research area is mainly from Hun River, and the contribution rate is47.07%; Nitrate nitrogen is mainly from top soil vertical infiltration, and thecontribution rate is52.39%.