Investigation of Groundwater Quality in Gotvand Aquifer with Emphasis on Nitrate Concentration

Gotvand Aquifer is one of the aquifers, water resources of which are mainly used for agricultural purposes. To evaluate the water quality of this aquifer with emphasis on nitrate pollution, samples were taken from eleven wells in June 2020. Field parameters (temperature, pH and EC) were recorded and the concentrations of major elements (Ca2+,  Mg2+, Na+, K+-,Cl-,SO42-, CO32-, and HCO3-) and nitrate were measured. The results showed that the spatial distribution of nitrate ion almost follows the direction of groundwater flow in Gotvand aquifer and shows a decreasing trend as moving from the upstream in the northern and western parts to the end of the flow lines in the east and southeast. Ion ratios, , , and , showed that the increase in chloride and sulfate ions, beside the natural tectonic factors, is caused by human activities. In the statistical analysis of the main components, the first and second factors respectively contributed to 47.7% and 32.2% of the total changes. The predominant type of groundwater is sulfate-calcium. In general, changes in nitrate ion concentration in groundwater of Gotvand aquifer have been affected by the size of soil texture in the area, groundwater depth, irrigation and drainage network, domestic sewage leakage and the use of chemical fertilizers.