Nitrate contamination in groundwater in the Sidi Aïch–Gafsa oases region, Southern Tunisia

• Published in: Environmental earth sciences Vol. 70; no. 5; pp. 2335 - 2348
• Main Authors: Hamed, Younes, Awad, Sadek, Ben Sâad, Amina
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-11-2013; Springer Berlin Heidelberg; Springer; Springer Nature B.V
• Subjects: Agriculture; Agrochemicals; Aquifers; Biogeosciences; Contamination; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environmental Science and Engineering; Exact sciences and technology; Geochemistry; Geology; Groundwater; groundwater contamination; Groundwater irrigation; Groundwater levels; Groundwater management; Hydrogeology; Hydrology. Hydrogeology; Hydrology/Water Resources; Nitrate content; Nitrates; nitrogen; Oases; Original Article; Pesticides; Pollution, environment geology; Resource management; salinity; Tapping; Terrestrial Pollution; tracer techniques; Water analysis; Water quality; Water resources; Water sampling; water table; wells; Tunisia; North Africa; Africa; Hydrochemical data; Nitrate; Tunisia; Groundwater salinity; Gafsa oases; salinity; fertilizers; nitrogen; tracers; shallow aquifers; ground water; water table; concentration; nitrates; pollution; contamination; agriculture; water quality; pesticides
• ISSN: 1866-6280; 1866-6299
• DOI: 10.1007/s12665-013-2445-5

Groundwater pumped from the semi-confined Complex Terminal (CT) aquifer is an important production factor in irrigated oases agriculture in southern Tunisia. A rise in the groundwater salinity has been observed as a consequence of increasing abstraction from the aquifer during the last few decades. All sources of contamination were investigated using hydrochemical data available from the 1990s. Water samples were taken from wells tapping both the CT and the shallow aquifers and analyzed with regard to chemistry tracers. Hydrochemical and water quality data obtained through a sampling period (December 2010) and analysis program indicate that nitrate pollution can be a serious problem affecting groundwater due to the use of nitrogen (N) fertilizers–pesticides in agriculture. The concentration of nitrate in an groundwater-irrigated area in Gafsa oases basin was studied, where abstraction from an unconfined CT aquifer has increased threefold over 25 years to 34 million m³/year; groundwater levels are falling at up to 0.7 m/year; and groundwater is increasingly mineralised (TDS increase from 500 to 4,000 mg/L), with nitrate concentrations ranging from 16 to 320 mg/L.