Distribution of groundwater nitrate contamination in GIS environment: A case study, Sonqor plain

Background: Nitrate is a pollutant of groundwater resources which can results health risks such as methemoglobinemia and formation of nitrosamine compounds in higher concentration limits. The present study was aimed to determine the nitrite level, causes of pollution and zonation of nitrite concentration in drinking water resources in the villages of Sonqor.   

Methods: In this descriptive-analytrical study, 73 samples of all groundwater resources of Sonqor plain were taken in ,high water (March 2010) and low water (September 2011) periods. Water nitrate levels were then determined by spectrophotometry. Results were compared by national standards and analyzed by SPSS and Arcview GIS 9.3 software. Finally, the concentration distribution mapping was carried out in GIS environment and the factors affecting nitrite changes were analyzed. 

Results: nitrate concentration of water resources of Sonqor plain was fluctuating at 3.09-88.5 mg per liter.In one station, nitrite concentrations in the high (88.5 mg/liter) and low (71.4 mg/liter) water seasons were higher than the maximum limit. Based on the maps, a relatively high concentration of nitrite was observed in the Eastern and Southeastern regions. 

Conclusion: The findings indicated a reverse correlation between nitrite concentration changes and changes of static surface depth. Low thickness of alluvium, location of wells in the downstream farmlands, farming condition of the region, nitrate leaching from agricultural soils and wide application of nitrogen fertilizers in agriculture were considered as the causes of the pollution in one station.