陕北地区地降水量小、蒸发强烈。神木县做为榆林市的能源基地中心，其周边既是煤炭及相关能源化工企业的分布区又是居民生活集中区，居民生活以及农业生产产生大量的污染物。本文以神木县大保当镇城区及周边为研究对象，利用调查所取得的资料及水化学与水质分析测试数据，对区内的地下水化学特征与规律进行分析，对地下水质量及其污染程度进行评价，并对地下水化学特征及污染成因进行了一定的研究，为寻找优质饮用水源和保护地下水提供了科学依据。 　　　得出了地下水化学特点的规律如下：在丘陵区和河谷区水化学类型分别为重碳酸型及重碳酸硫酸重碳酸氯化物型。在地下水径流方向TDS及各主要离子含量由河谷区向丘陵区逐渐减小，并且TDS浓度与潜水面海拔成反比。 　　　对研究区地下水水化学数据进行全面分析，得出三氮污染为地下水的主要污染成分。利用模糊综合评价方法对地下水质量进行评价，并使用Grubbs检验法及数理统计法研究各组分地下水环境背景值，对地下水污染进行评价，结果表明：丘陵区潜水水质优于河谷区，是当地居民寻找较好饮用水源的目标；研究区地下水污染主要为NO3-N的污染，并且污染主要集中在秃尾河及其较大支沟的沟谷区。 　　　通过对地下水水化学及污染成因分析可得：研究区地下水水化学成分形成的主要原因是溶解沉淀作用、地下水径流、蒸发浓缩三种作用的共同结果。通过对潜在污染源及地下水防污性能的分析，研究区内潜在污染源及污染比较严重的地段均为秃尾河河谷及其各大支沟的沟谷区。研究区主要污染为NO3-N的污染，其主要影响因素为污染源、地下水蒸发浓缩、以及地下水氧化还原环境，其中地层垂向上NO3-N污染主要集中在地下水位埋深小于10.0m的含水层之上，说明包气带厚度大于10.0m的地下水不易遭受污染。 　　　通过本文对区内地下水水化学及污染方面的研究，研究结果可以为大保当镇地下水水资源合理利用及开发以及区内寻找优质饮用水源提供科学依据。

In northern Shaanxi area, the precipitation is very little and the evaporation is intense.As the center of the energy base in yulin,its surroundings areas are the concentration of the energy companies and residents living,at the same time agricultural and livestock production are more in this regions.da bao dang town of shen mu 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 assement and analysis of groundwater,water chemistry and cause of pollution,to area residents looking for high quality drinking water source,and the rational exploitationand utilization and protection of groundwater resources and provide a scientific basis. 　　　Through the study of groundwater chemical composition characteristics,draw a conciusion that:Generally speaking,river valley area are main type of HCO3.SO4and HCO3.CL,hilly area of groundwater chemical types are HCO3. Ca, in the groundwater flow direction the thickness of TDS is inversely proportional to the driver,s elevation sea level,TDS and main ion appears by valley area to upland along the groundwater flow direction gradually decreased. Using a series method,the study area groundwater chemical test data were analyzed,the three nitrogen in groundwater area to the main pollution composition.using the fuzzy comprehensive evaluation method of groundwater quality evalution,and use of the Grubbs testing method and the mathematical statistic method to study the components of the groundwater chemical background value,based on the single factor pollution in-dex method to groundwater pollution was evaluated, the result show that：the quality of the hily area is better than valley area.local residents are looking for good drinking water source to the object of the study area;groundwater pollution are mainly NO3-N pollution,and pollution areas mainly concentrated in the Tuwei River Valley area and 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 dissolve and sediment interaction,the runoff of groundwater,vaporation 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 ,lots of serious pollution for Tuwei river valley area and major branch gully rvine area .Study on thepollution of NO3-N main influence factors: source of pollution,groundwater evaporation and groundwater redox environment,in which the longitudinal NO3-N pollution mainly concentrated in the water depth is less than 10.0m horizon,showthat it is not easy polluted when the thickness of aeration zone more than 10.0m . 　　　Spread out underground water chemistry and water pollution in the area .the results of this study can be for rational development and utilization of groundwater and looking for source of high quality drinking water,at the same time provide scientific basis for.