Research Of Groundwater Chemical Characteristics And Nitrate Pollution Source Of Yaoxian Map-area

Yaoxian is located southeast of Tongchuan C ity, Shaanxi Province, the degree of its groundwater exploitation is very large, and the groundwater is the basic drinking water for its villagers, so the study of groundwater contamination in the area is necessary. This paper systematically studied the topography, hydrogeological and groundwater recharge conditions of Yaoxian region; with the method of water chemical analysis, therefore we can reveal the variation of groundwater chemical characteristics within the region. Then give classification to the groundwater according to the water quality report, so we can conclude that water pollution is mainly caused by nitrate ions. Finally, use the Factor Analysis methods to get the concrete analysis of the pollution sources from nitrate nitrogen. The major conclusions we have drawn are as follows:(1) The hydrochemical types of different water are mainly containing HCO3-、Na+、Ca2+、Mg2+ which is 52 percent of the total water types, second for the types of HCO3-、Na+ and HCO3-、Na+、Mg2+ with Na+ and Ca2+ being the main cations and HCO3- being the main anion. Besides natural process of different aquifer rock,anthropogenic activities which is mainly expressed agricultural activities in this region also plays an critical role in hydrochemical compositions.(2) According to the results of the ions tests, 3 is the most important ion with excessive rate being 22.5% and nearly nothing of 4 and NO2-. Thus, NO3- is the main pollutant among the triple-nitrogen.(3) Factor analysis method is used to analyse 9 ions as Cl-、SO42-、HCO3-、Ca2+、Mg2+、PO43-、NO3-、F- and Na+, finally we can get 3 common factor that give the most contribution to the contribution rate. Ca2+、Mg2+、Cl-、SO42- and NO3-are the most outstanding in factor 1 while PO43- belongs to factor 3,which can reflect the influence of anthropogenic activities on groundwater. Na+ and HCO3- gather in factor 2 which can reflect the influence by natural processes.(4) Make a superposition graph of NO3- and land use types which contains farmland, urban, mixed use land and useless land, the result is that farmland has the most serious nitrate pollution, the next are urban and mixed use land.