Groundwater Chemistry of the Mornag Aquifer System in NE Tunisia

Abstract

The present paper investigates hydrochemical processes and water quality in the Mornag aquifer in NE Tunisia. Groundwater samples were collected during a field campaign, and were analysed for major and trace elements. The collected waters have a chemical facies rich in Ca 2+, Na + and Cl -. Piper diagram shows a progressive increase in chloride ions along with increasing salinity. Saturation indexes calculated by using PHREEQC (USGS) show that the Mornag waters are slightly saturated with respect to carbonates (calcite and dolomite), while undersaturated with respect to gypsum, halite and other evaporitic minerals. The current composition of waters takes place via dissolution of halite and Ca-sulfates, where the increase in calcium is partially balanced by possible calcite precipitation. The relevant recorded pollutant is nitrate, which was likely dispersed from agricultural soils, while heavy metals were generally far below values of pollution thresholds, indicating no influence by mining activity.

Hydrochemical Diversity of a Large Alluvial Aquifer in an Arid Zone (Draa River, S Morocco)

“…Similar concentrations of macrocomponents in groundwater were also established for other Moroccan areas [3,6,30]. However, the values recorded in alluvial waters of the Draa river were higher than in Oman [31] or Tunisia [7].…”

“…SI values recorded for halite displayed a trend pointing to this mineral as the principal source of Na + and Clsupplied to groundwater. The mainly halite-dissolution origin of these ions in alluvial waters was also reported by [7] and [16]. Chloride ions may have also derived from dissolving of sylvite, evidenced by SI < 0, or weathering of carbonate and clay rocks.…”

“…This issue is of particular importance in hot arid areas, groundwater of which shows high salinity resulting from geogenic processes [1,2]. An increasing number of studies also points to high nitrate concentration caused by human activity [3][4][5][6][7]. Therefore, it is crucial to investigate the variations, often observed even on small areas, in the chemistry of waters to assess their suitability for irrigation [5,6,8,9] and drinking purposes [5,10].…”

Chemical composition of utility water in the arid climate zone on the examples of Kébili and Medenine regions (southern Tunisia)

“…Halite is the most frequent manner of enhancing water with Na and Cl ions (i.e. Farhat et al 2010;Warner et al 2013). It can be easily and quickly dissolved.…”

“Not seen, not considered”: mapping local perception of environmental risks in the Plain of Mornag and Jebel Ressass (Tunisia)

“…This territory includes 20,000 ha of agricultural land (8660 ha of which is irrigated; Hamrita et al 2017) that is among the most productive and most agro-export-oriented in Tunisia (Perez 1992;Ben Romdhane 2011). Indeed, the Mornag plain is a privileged area of intensive arboriculture (Zeramdini et al 1996;Aïachi Mezghani et al 2012) with relatively good soils and unusually shallow groundwater access compared to the rest of the country (Farhat et al 2010a, b) as well as a comparatively very good transport network (it is less than 30 km south of Greater Tunis, to which it is connected through roads, a railroad, and a highway). Olives have been grown in this region since the time of Carthage (Leveau 2007a, b).…”