Hydrochemical investigations of groundwater have been carried out on objectives of evaluating groundwater quality. Groundwater quality contaminations have emerged in many geographical areas due to natural environmental processes and human intervention in the geosystems. Geochemical evaluation of nitrate contaminated groundwater in Gulf region was investigated. Results showed that most of the samples contained high concentrations of nitrate. More than 70% of samples in central area contained high concentration of nitrate. Furthermore, results show that nitrate has a negative relationship with calcium and sodium, whereas relationship with magnesium, potassium, alkalinity, sulphate, chloride and electrical conductivity (EC) are positive. Factor analysis was used to identify key parameters that described the groundwater quality. Two factors were extracted as follows: Factor 1 explained 60% of the total variance, reflected the importance of the intrusion of salt water into the groundwater and factor 2 explained 35% of the total variance, and reflected impact of human activities and acid-rain recharge of the aquifers in the area. The geochemical modeling reveals that the high nitrate groundwater behaves like two kinds of the mechanism of hydrogeochemical evolution, namely the intervention of human activities, and the evaporation effect of the shallow groundwater.

Key words: Groundwater, geochemical, factor analysis, nitrate, drinking water.