Hydrogeochemical processes and nitrate contamination of shallow groundwater in the Gareb-Bouareg region, northeastern Morocco

Abstract

In semiarid regions, groundwater faces considerable challenges due to both natural and human-induced contaminants, including nitrate contamination. These issues impact the availability of groundwater, a vital resource. Therefore, it is crucial to identify the sources and mechanisms contributing to salinization and nitrate contamination. In this study, we examined the hydrogeochemical characteristics of shallow groundwater in the Gareb-Bouareg region, northeast Morocco. The aim was to determine and understand the key processes that govern its chemical composition and assess nitrate contamination. A total of 50 groundwater samples were collected from existing wells and analysed for major cation and anion concentrations. The results showed that the dissolution of evaporite minerals, cation exchange and evaporation are the predominant processes of groundwater mineralization. In 72% of the samples, nitrate concentrations surpassed the anthropogenic origin threshold value of 10 mg/L, while 16% of the samples exceeded the drinking water standard of 50 mg/L. The highest values were found in the rural and urban areas, at 122 mg/L and 84.24 mg/L, respectively. Nitrate levels and the depth to the water table reveal the impacts of surface contamination sources. The spatial distribution and interrelationship between nitrate and other parameters suggest possible distinct origins of dissolved nitrates associated with various anthropogenic activities.