Research Of Groundwater Chemical Characteristics And Pollution In The City Of Yanan And Its Surrounding Areas

Yanan city is the old revolutionary base areas, located in Loessial Gully Hill Area, the shortage of water resources, water resources per capital is only277.8m3. The water supply of Yanan Municipal Area depends mainly on the Xingzi ditch Wang Yao reservoir and Hongzhuang ditch reservoir, but in the water supply network can not access the city fringe or higher areas, residents living water rely mainly on local dispersed mining groundwater, Yanan city and the surrounding areas of groundwater has become a local inhabitant’s important life water. This paper relies on the China Geological Survey Bureau issued a" in the main city of groundwater pollution investigation and evaluation in Northern Shaanxi" project of major city northwest of groundwater pollution investigation and evaluation of the project (1212011121165)",Yanan city and the surrounding area as the research object, make full use of survey data obtained and water chemistry and water quality analysis of test data, the study area groundwater water chemical characteristics and laws, on groundwater quality and pollution assessment and analysis of groundwater, water chemistry and the cause of pollution, to area residents looking for high quality drinking water source, and the rational exploitation and utilization and protection of groundwater resources and provide a scientific basis.Through the study of groundwater chemical composition analysis, the study area groundwater chemical characteristics exhibited significant regional variation:Generally speaking, hilly area of groundwater chemical types are type groundwater, river valley area are main types of HCO3· SO4and HCO3· Cl (or Cl· HCO3), TDS and main ion appears by upland area to valley along the groundwater flow direction gradually increased, and in the groundwater flow direction on the TDS more high diving, the diver’s elevation above sea level is low. In Yanhe River each branch channel upstream or ditch brain lot NO3-N concentrations are low, the concentration of NO3-N content high point distribution in Yanhe River Valley area and urban area; study of NO2-N detection point distribution in Yanhe River and its larger basic branch ditch Valley area.Using correlation analysis, cluster analysis and factor analysis methods, the study area groundwater chemical test data were analyzed, the three nitrogen in groundwater area to the main pollution composition. Of each sampling water chemical data of Q type cluster analysis showed that:the chemistry of water sample has two major group, a group of basic is distributed in smaller river affected by human activities each small branch channel upstream section; another group of basic distribution in Yanhe River and the big ditch valley areas, these areas it is population compared with the aggregation or field distribution is more densely populated region.Using the fuzzy comprehensive evaluation method of groundwater quality evaluation, and the use of Grubbs testing method and the mathematical statistic method to study the components of the groundwater chemical background value, based on the single factor pollution index method to groundwater pollution was evaluated, the results show that:the hilly area groundwater quality is relatively good, local residents are looking for good drinking water source to the direction of the study area; groundwater pollution are mainly NO3-N pollution, followed by Cl-and SO42-pollution, and pollution areas mainly concentrated in the Yanhe River Valley area and its major branch gully ravine area.Based on the groundwater chemistry and pollution causes analysis shows:the chemical composition of water of the study area are mainly formed into water and aeration zone and aquifer rock and soil water rock interaction, hydrodynamic condition of ground water, evaporation and concentration effect and the joint effect of human activity. The potential sources of contamination and groundwater vulnerability analysis, the study area source of pollution in the main distribution area, groundwater vulnerability weak lots and lots of serious pollution for Yanhe valley area and its major branch gully ravine area. Study on the pollution of NO3-N main influence factors:source of pollution, environmental hydrogeological factors (water depth, vadose zone lithology, groundwater dynamic condition), groundwater evaporation and groundwater redox environment, in which the longitudinal NO3-N pollution mainly concentrated in the water depth is less than15m horizon.Spread out underground water chemistry and water pollution in the area of study for the first time in study area, the results of this study can be for residents looking for high quality drinking water sources for Yanan city groundwater resources, rational development and utilization of groundwater pollution and provide scientific basis for.