Nitrate contamination in deep aquifers: Health risks and spatiotemporal analysis in an arid region of the Algerian Sahara

The health of consumers can be adversely affected by the increased nitrate concentration in water resources as a result of human activities and the lack of wastewater management. This study evaluates the quality of groundwater and the extent of nitrate contamination in the Oued Righ Valley of Algeria, an arid region that is experiencing significant urbanization and agricultural activity. The physicochemical parameters of 167 water samples, including pH, conductivity, and nitrate (NO 3 - ) levels, were analyzed between 2014 and 2022. Sampling analysis was conducted with classical physicochemical methods and health risk based on chronic daily intake, and the hazard quotient (HQ) of nitrate intake from drinking water was determined. Results indicate a weakly alkaline groundwater with conductivity levels exceeding WHO guidelines. Spatial analysis shows elevated nitrate concentrations, especially in the southern region. The temporal pattern of annual average nitrate concentration during 2014–2022 showed a significant increase with a slope of 1.04 mg/L year -1 . Health risk assessments show that nitrate levels exceed the non-carcinogenic hazard threshold for vulnerable groups, particularly children and infants, in 7% of samples with an average of 1.31. The risk was 41.17% (21 times) in infants, 25.49% (13 times) in children, 19.60% (10 times) in adolescents, and 13.72% (7 times) in adults. Only the southern part had the maximum occurrence, with 82.35% (42 times) of samples exceeding the threshold 1 recommended by WHO. A land use analysis using the Land Change Modeler revealed that agricultural and urban land increased over the study period, correlating with rising nitrate levels. These anthropogenic influences, such as urban wastewater and fertilizer use, contribute to pollution, particularly in the southern area. These findings highlight the need for sustainable water management practices to mitigate nitrate contamination and its associated health risks. • The groundwater is weakly alkaline with conductivity levels exceeding WHO guidelines • Spatial analysis shows elevated NO 3 levels, especially in the southern region • Temporal pattern of NO 3 showed a significant increase with a slope of 1.04 mg/L year -1 • NO 3 levels exceed the non-carcinogenic hazard threshold for children and infants