Assessment of groundwater quality and suitability with emphasis on the human health risk in North African Saharan oases: a case study from the Tozeur region, southern Tunisia

• Published in: Euro-Mediterranean journal for environmental integration 2022-06, Vol.7 (2), p.223-239
• Main Authors: Tarki, Meriem, Dadi, Kamel, Dassi, Lassâad
• Format: Article
• Language: English
• Subjects: Adults; Agricultural management; Agricultural practices; Agricultural production; Aquatic Pollution; Aquifers; Atmospheric Protection/Air Quality Control/Air Pollution; Cation exchange; Cation exchanging; Children; Contamination; Drinking water; Earth and Environmental Science; Earth Sciences; Environmental Chemistry; Environmental degradation; Environmental impact; Environmental Management; Environmental protection; Environmental risk; Environmental Science and Engineering; Evaluation; Fluorides; Groundwater; Groundwater pollution; Groundwater quality; Health hazards; Health risk assessment; Health risks; Ingestion; Irrigation; Irrigation water; Magnesium; Mineralization; Nitrates; Oases; Original Paper; Overexploitation; Permeability; Public health; Quality assessment; Quality control; Return flow; Risk reduction; Sediments; Sodium; Waste Management/Waste Technology; Waste Water Technology; Water analysis; Water hardness; Water Management; Water Pollution Control; Water quality; Water sampling
• ISSN: 2365-6433; 2365-7448
• DOI: 10.1007/s41207-022-00312-8

The Tozeur Saharan oases represent one of the most vulnerable systems at risk, as inefficient agricultural practices and groundwater overexploitation in these oases have resulted in environmental threats linked to water quality degradation. In this study, hydrochemical analyses were used to assess the groundwater quality and mineralization processes, appraise the suitability of the water for drinking and irrigation purposes, and evaluate its human health risk. It was demonstrated that the groundwater mineralization is mainly controlled by water–rock interaction processes, i.e., the dissolution of evaporates and cation exchange processes, the irrigation water return flow, and the intrusion of chott brines. Groundwater quality assessment based on the total hardness (TH), water quality index (WQI) and entropy water quality index (EWQI) showed poor water quality and very hard groundwater. However, the majority of the groundwater samples were suitable for irrigation in terms of the sodium absorption ratio (SAR), sodium percentage (Na%), permeability index (PI), potential salinity (PS), Kelley ratio (KR) and magnesium ratio (MR). Nitrate and fluoride were evaluated to estimate the noncarcinogenic health risk when groundwater is consumed by children and adults using the United States Environmental Protection Agency (USEPA) method. Fluoride concentration exceeded the permissible limit (1.5 mg/l). The total hazard index (THI) calculated for children and adults indicated that 100% and 31% of the samples, respectively, presented a health hazard (THI > 1). These values confirmed that children are more vulnerable through direct ingestion of drinking water than adults. Consequently, pressing measures must be taken to reduce the risks of contaminated groundwater on public health.