State of nitric pollution of the Mnasra aquifer, coastal zone of the Gharb plain (Morocco)

Abstract

Summary Nitrates are highly soluble and highly mobile chemical elements in water. Their presence in groundwater with high concentrations frequently indicates anthropogenic contamination. They come mainly from the massive use of nitrogen fertilizers or unpurified urban waste. A physicochemical characterization of the nitrate and ammonium contents of the waters of the Mnasra aquifer was carried out following the sampling of 70 wells and boreholes during the months of June and July 2017. The results show high concentrations of nitrates, 82.85% of the wells taken will exceed the potability standard (50 mg / l). This is confirmed by the coarse nature and sandy soil texture that can promote nitrate leaching, the low water table in this region (70% of wells with depths less than 20 m), and the massive use of soil. fertilizers and fertilizers. The analysis of temporal trends in nitrate concentrations observed over 23 years showed a significant degradation of the water quality of wells between 1993 and 2017 with excessive levels reaching five to six times the potability limit.