Seasonal Assessment of Nitrate, Nitrite, and Heavy Metals Pollution in Groundwater of Ardabil Aquifer, Iran

One of the most important resources for drinking water is groundwater. Recently, the quality of groundwater has been endangered due to several reasons, including human activities, vast agricultural activities, and the discharge of industrial wastewater containing nitrogen (N) and heavy metals. For this study we investigated the values of NO3, NO2, and some heavy metals and analyzed the groundwater of the Ardabil Aquifer area in wet and dry seasons. For this purpose we evaluated 76 wells in the study area. In order to analyze the results we used World Health Organization (WHO), U.S. Environmental Protection Agency (EPA), and Institute of Standard and Industrial Research of Iran (ISIRI) standards. The results indicated that, according to WHO and ISIRI, 10.5% of wells and, according to the EPA, 69.7% of wells have NO3 above the standard level in the wet season, but in the dry season, according to WHO and ISIRI, 29% and, according to the EPA, 80.6% of the wells have NO3 above the permissible level. However, according to all standards, NO2 values are less than the permissible level for drinking consumption. In terms of evaluation criteria of the simultaneous presence of NO3 and NO2 in drinking water (K), 29% of wells in the dry season and 13.15% of wells in the wet season have NO3 and NO2 problems. In order to find an appropriate interpolation method and zoning parameter of NO3 and NO2, different interpolation methods were evaluated and Kriging method with the lowest error was chosen for zoning the parameters. According to zoning maps, in the wet season the Namin and south Ardabil areas, which have the most drinking water wells, contain values of NO3 above the permissible levels, whereas the values of NO3 are at the mediocre level in the dry season. In addition to NO3 and NO2 analysis, the evaluation of heavy metals pollution indices in the aquifer include: heavy metal pollution index (HPI), heavy metal evaluation index (HEI), and contamination degree (Cd). Generally, according to the EPA, in terms of NO3 and NO2 pollution, Ardabil aquifer is in an undesirable condition, and according to WHO and ISIRI standards, this area has a mediocre level of undesirable condition. According to HPI and Cd indices, most parts are in a high class of heavy metal pollution, as well.