Investigation of hydrogeochemical characteristics of groundwater of Naqadeh plain aquifer and heavy metal pollution index (HPI)

Naqadeh plain located in the southwestern part of Urmia Lake has suitable water resources. In recent years, agricultural development and increasing industrial units, in addition to inadequate disposal of urban, industrial and agricultural wastewater to the Gedar River, increase the risk of groundwater contamination. In order to monitor the groundwater resources of this plain, 33 water samples from exploitation wells were collected during July 2016. Hydrochemical parameters and the concentration of the major, minor and heavy metals elements of collected samples were analyzed. In order to identify the origin of heavy metals and the related geogenic and anthropogenic pollution sources of them, hydrochemical diagrams, statistical analysis, spatial distribution maps and geological interpretations were used. The results indicate the concentration of some parameters including EC, and heavy metals include, Fe, Mn, and Al are higher than the international standard limits. HPI was used to understand the drinking quality of groundwater resources in regard to the concentrations of six heavy metals. Classification results show a good quality for 70% and inadequate quality for 30% of the samples. The total HPI index of Naqadeh plain is 23.24, which is lower than its critical values(100). Also, the highest HPI of sampling points with values of 161,220 and 871 threaten human health. High concentrations of heavy metals can be related to the dissolution of geological formations, mining of iron ore, and the activity of industrial units and the condensation of elements in groundwater due to high evaporation in areas with a low depth of groundwater.