A GIS Survey of Trends for Nitrate Concentration in Drinking Water Sources, Rural Areas of Qom Province, Iran

The purpose of this study was surveying the trends of nitrate variations in drinking water of rural areas of Qom province and its mapping using GIS software. This study was of descriptive cross-sectional type. The collected data related to nitrate concentrations during years 2006-2011 were acquired from Qom Province Rural Water and Wastewater Company. During the year 2012, 73 wells were tested via two sampling runs; one sampling set performed in wet season and the other one carried out in the dry season. Nitrate concentrations were determined spectrophotometric ally. The Chi-squared test and segmented regression model were used for data analysis. Four software’s, namely, Excel-2007, SPSS-16 and Joinpoint-4.1, were used for data mapping and analysis. The average nitrate concentration during 2006-2012 period was 23.12 mg/L with the standard deviation of 18.68 mg/L. 7.5% and 4.9% of the surveyed wells were “at risk” and “contaminated”, respectively. Regression results indicated a lack of sufficient statistical evidence to accept an increasing trend of nitrate during the study period (P value=0.85). There was no significant difference in the contamination averages between the results of two sample sets which were taken during each year. During the beginning of 2006 to the beginning of 2013, an increasing trend of nitrate concentration was observed in the contaminated wells. In the majority of monitored wells, the nitrate concentration was in the standard range. In the “at risk” wells and also in the others, the concentrations were beyond the standard levels. Therefore, Management approaches should be applied to avoid the nitrate penetration into the aquifers.