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

Water pollution by nitrate has become increasingly a serious problem in coastal countries. Agricultural activities are probably the most significant anthropogenic sources of nitrate contamination in groundwater. Mnasra is the largest agriculture irrigated zone in the plain of Gharb, well known for its intensive agricultural activities. The excessive use of fertilizers and manure under gravity irrigation system especially for sandy-loam soils similar to those of the area. The present study was the evaluation of nitrate concentration in groundwater, and know the probable origins of this contamination, for this purpose, A physicochemical characterization was carried out following the sampling of 63 wells and 7 boreholes. The results show high concentrations of nitrates, 85% of the wells taken will exceed the potability standard (50 mg / L). 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 limits the potability limit. This is confirmed by the coarse nature and sandy soil texture that can promote nitrate leaching, the low piezometric level in this region, the type of irrigation and the massive use of soil and fertilizers.