『Abstract
　A total of 95 groundwater samples were collected from Toyserkan, western Iran to assess the chemical composition and nitrate (NO3^-) status of groundwater. The most prevalent water type is Ca-HCO3 followed by water types Ca-Mg-HCO3. In comparison with the World Health Organization (WHO) drinking water guideline of 50 mg l^-1 for NO3^-, a total of nine wells (9.5％) showed higher concentrations. In 36％ of samples (34) NO3^- concentration was low (＜20 mg l^-1), and in 53.7％ of samples (51), in the range of 20-50 mg l^-1. The samples were classified into four groups based on NO3^- and chloride (Cl^-1) concentrations. Of the samples, 40％ were classified as group 4 and were relatively high in Cl^- and NO3^- (Cl^-＞47 mg l^-1, NO3^-＞27 mg l^-1). The high correlation between NO3^- and Cl^- (r = -.86, p＜0.01) is consistent with a manure source, resulting from the practice of adding salt to animal feed. Pollution of groundwaters appeared to be affected by the application of inorganic fertilizer at greater than agronomic rates, Cl-salt inputs, and irrigation practice.

Keywords: Groundwater; Nitrate; Pollution; Water quality; Agriculture』

Introduction
Materials and methods
　Study area
　Sampling method
Results and discussion
　Major ion chemistry
　Hydrochemical facies
　Chloride and NO3^- concentrations in groundwater
　Water classification
Conclusions
References