Assessment of nitrate contamination and groundwater suitability in a hyper-arid region using GWQI, PCA, and geochemical tools

Groundwater contamination, particularly nitrate pollution, poses serious health and environmental risks in hyper-arid regions, where water scarcity compounds these challenges. Despite its critical importance, comprehensive frameworks for assessing groundwater quality, focusing on nitrate contamination, remain limited. This study aims to evaluate nitrate contamination and overall suitability of groundwater for drinking and farming purposes in the hyper-arid Adrar region of southwestern Algeria, where salinity and nitrate pollution pose significant risks. One hundred and thirty groundwater specimens were gathered and analyzed for 12 physicochemical features. To assess contamination sources and water quality, an integrated approach combining the groundwater quality index (GWQI), principal component analysis (PCA), and geochemical tools (Gibbs and Piper diagrams) was applied. Results indicate that 80% of the samples were deemed to be in 'extremely poor' condition (GWQI > 150), with a mean total dissolved solids (TDS) concentration of 1,484.70 mg/L and nitrate concentrations averaging 43.05 mg/L, both of which exceed World Health Organization standards. PCA identified salinity (47.33% variance) and nitrate contamination (9.95% variance) as the primary contributors, which are linked to mineral dissolution and agricultural inputs. The findings underscore the urgent need for sustainable water management and provide a replicable model for assessing groundwater quality in similarly challenged regions.