تغییرات زمانی و مکانی غلظت نیترات و نیتریت منابع آب آشامیدنی شهرستان کهگیلویه با استفاده از سیستم اطلاعات جغرافیایی(GIS)

Background and purpose: Nitrate is one of the pollutants of groundwater resources which is easily found in agricultural and wastewater disposal areas. The aim of this study was to determine the spatial and temporal variations of nitrate and nitrite in drinking water resources of Kohgiluyeh -a city in Iran- using Geographic Information System (GIS). Materials and methods: This cross-sectional study was carried out in 2011 in which 18 sources of drinking water (108 samples) and results of five-year-archived analysis in Water and sewage Co of Kohgiloyeh were studied applying GIS software ver. 9.3, SPSS ver. 16, and Pearson correlation test. Results: The results showed that the mean of nitrate concentration in 2007 was 18.5 ± 1.5 and in the summer and fall of 2011 was 20 ± 4.6 and 20.83 ± 2.2 ppm, respectively which indicates a direct correlation between years and the increase in nitrate concentration (R= 0.92, P= 0.01). However, the nitrite concentration was found steady in most years. The spatial variations represent worse quality of northwest. Ordinary kriging is the best interpolation method for nitrate and nitrite. Conclusion: According to the results, the concentration of nitrite and nitrate has increased during the past years and in some parts are even rising more than the standard levels. The reasons could be regional geology and agricultural and to prevent such problems protecting the wells, using river water for agriculture, and construction of wastewater treatment plants could be of great benefit.