Quality zoning of seasonal changes in nitrate and ammonia in drinking water wells of Babol city using GIS system

Underground water resources constitute an important part of urban water resources. One of the serious challenges in ensuring and promoting community health is gradual increase in nitrate levels of drinking water of communities across the world. The purpose of this study was to investigate the seasonal variation of nitrate and ammonia levels in drinking water wells of Babol city using GIS software, in 2010-11. This cross-sectional analytical study was performed on drinking water wells of Babol city in 2010-11. Sampling was done according to a standard method from 20 drinking water wells, in different seasons; and in final, 80 water samples were analyzed. Nitrate and ammonia concentration of samples was measured using Spectrophotometer DR2000 (Hach company) in 500 and 425 nm, respectively. For qualitative analysis and seasonal fluctuation of nitrate and ammonia concentration of different areas, Geographic information systems, ArcGIS, was used. The results showed that the highest amount of nitrate was in summer (23.68 mg/l), and the lowest was in winter (14 mg/l). While the highest and the lowest amount of ammonia was in spring (0.43 mg/l) and summer (0.06 mg/l), respectively. Also, the results showed that only in well number 5 located in Kate Sofla village, nitrate concentration had increasing trend, and in the remaining wells, nitrate and ammonia concentration, had an increasing and a decreasing trend, respectively. The results indicate that nitrate and ammonia levels in all samples were lower than the WHO recommendations. To avoid increasing in the ammonia and nitrate concentrations in the underground waters, ongoing training to farmers on the proper use of chemical fertilizers, as well as the construction and operation of wastewater collection systems are recommended.