以内蒙古乌拉盖地区地下水为研究对象，综合利用水化学计量分析、多元统计分析、空间统计分析及氧化还原分析等，开展区域地下水水化学特征及成因研究。结果表明：研究区地下水水化学特征存在显著的空间变异性；水岩作用是控制水化学演化的主要因素，蒸发浓缩及离子交换作用次之；硅酸岩风化是主控的水岩作用，碳酸盐岩溶解次之，蒸发岩影响较为微弱，这与区域地质背景相匹配；部分地下水存在硝酸盐污染，空间分析表明区域分散的农牧业及生活污水排放成为地下水硝酸盐污染的重要来源，氧化还原分析表明区域存在潜在的反硝化趋势。研究结果可为干旱及半干旱区地下水资源可持续开发利用提供科学依据。

The sustainable use of groundwater in arid and semi-arid regions is related to regional ecological security and food security.However,with the rapid development of social and economic construction,the exploitation of groundwater resources is significantly increased,which made severe water supply shortage.Likewise,the water resource problem caused by the water quality crisis are more serious than the reduction of water quantity.Carrying out research on groundwater chemistry in arid and semi-arid areas not only had important academic significance for clarifying the origin and formation of groundwater but also had important value for scientific and reasonable regional groundwater development and protection of groundwater resources. This research took Wulagai area of Inner Mongolia as the research area,and comprehensively utilized water stoichiometric analysis,multivariate statistical analysis,spatial statistical analysis,and redox analysis to carry out regional groundwater hydrochemical characteristics and causes. The results showed that the groundwater hydrochemical characteristics had significant spatial zoning characteristics.There were certain differences in the water chemistry of deep and shallow groundwater in different regions.The shallow groundwater in Zone 1 was Ca-HCO3 pattern (40%),the deep groundwater was Ca-HCO3 (38%) and Na-HCO3 patterns (38%);shallow groundwater in Zone 2 was also Ca-HCO3 pattern (57%),and deep water chemistry patterns had Ca-HCO3 (54%) and Na-HCO3 patterns (45%) .The types of water chemistry in Zone 3 were relatively diverse.The shallow groundwater was mainly a Ca-Mg-Na-HCO3 pattern (37%),other types were also distributed,and the deep groundwater was Ca-Na-HCO3 pattern (29%),respectively. Waterrock interaction was the main factor controlling the evolution of water chemistry in the study area,and there were still certain differences in different regions and stratifications.Among them,zone 3 was also affected by evaporation,concentration and ion exchange.The weathering of silicate rock was the main controlling effect in the water-rock interaction,followed by the dissolution of carbonate rock,and the influence of evaporite was relatively weak,which matched the regional geological background.Furthermore,factor analysis showed that human activities were also an important factor affecting the hydrochemical characteristics of groundwater.There was a certain amount of nitrate pollution in groundwater.Spatial analysis showed that nitrate in the whole area was a typical random distribution pattern,and there was no discrete and aggregation effect at the pollution point,which indicated that the regional dispersion of agriculture,animal husbandry and human activities become an important point source of groundwater nitrate pollution.Redox analysis showed that there was a potential denitrification trend in the area.The results provided a scientific basis and technical support for the sustainable development and utilization of groundwater resources in arid and semi-arid areas.