Global assessment of water quality and groundwater nitrate contamination in the region of Souss-Massa, Morocco A comprehensive review

Degradation affects many aquifers, impacting both their quantity and quality. Nitrate is the most prevalent groundwater pollutant because it dissolves easily in water and is difficult to fix in soil. This review aims to assess previous research on water quality in the Souss-Massa region (groundwater and surface water), highlight the degree of nitrate pollution recorded in this aquifer, and determine the origins of this contamination. Overall, all dams of the Souss-Massa aquifer showed excellent to good water quality in 2018. In contrast, the rivers indicated a decline in quality during the same year, except at the Aoulouz point, where dissolved oxygen content—reaching up to 4.5 mg/L—was responsible for this degradation. On the other hand, during the 2018-2020 campaign, the Souss aquifer and Chtouka aquifer showed moderate to bad quality due to nitrate concentrations and high mineralization. According to the boxplot diagram of statistical parameters of NO₃⁻ concentration and Nitrate Pollution Index (NPI) collected from previous studies, nitrate pollution recorded in this aquifer occurs in just some wells and not the entire aquifer, and this contamination is basically due to different origins like agricultural fertilizers, domestic wastewater, and manure.