Geochemistry and nitrate pollution assessment of groundwater in Djelfa city

Being part of the Algerian steppes, the Djelfa region is characterized by a semi-arid climate, where groundwater resources are very low. They are the only source for human, agricultural and industrial food. This study focuses on the Mio–Plio-Quaternary groundwater. Its purpose is to study the physicochemical parameters, the main chemical elements, the origin of the mineralization as well as the possible sources of pollution. To this end, 19 water samples were taken during the low water period (November 2019) and were subjected to physico-chemical analyzes to determine the parameters: T °C, EC, pH, TDS, Na + , Ca 2+ , K + , Mg 2+ , Cl − , SO 4 2− , HCO 3 − , and NO 3 − . According to Piper's diagram, 74% of the waters in the study area have chloride, calcium sulfate and magnesium facies; 26% are calcium and magnesium bicarbonates. To extract and visualize the important information contained in these multivariate data; principal component analysis synthesizes this information and has highlighted the main phenomenon of mineralization, which is essentially the dissolution of rock by contact with water. The high concentrations of nitrates (> 50 mg/l) in the study area come mainly from the fertilizers used, the excrement of sheep livestock, given the agricultural nature of the region and the presence of discharge points located near certain wells of water and the Djelfa–Mellah wadi.