Use of a time-domain electromagnetic method with geochemical tracers to explore the salinity anomalies in a small coastal aquifer in north-eastern Tunisia

• Published in: Hydrogeology journal Vol. 22; no. 8; pp. 1777 - 1794
• Main Authors: Chekirbane, Anis, Tsujimura, Maki, Kawachi, Atsushi, Lachaal, Fethi, Isoda, Hiroko, Tarhouni, Jamila
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.12.2014; Springer Berlin Heidelberg; Springer Nature B.V
• Subjects: Aluminum; Aquatic Pollution; Aquifers; Brines; Coastal; Coastal aquifers; Coastal plains; Coasts; data collection; Earth and Environmental Science; Earth Sciences; Electromagnetics; Ephemeral streams; Geochemistry; Geology; Geophysics; Geophysics/Geodesy; Groundwater; Hydrogeology; Hydrology/Water Resources; Oil and gas fields; Oil field equipment; oil fields; oils; Piezometric head; Saline water; Saline water intrusion; Salinity; Salinization; Salt water; saltwater intrusion; sea level; Sea water; Seawater; streams; surface water; surveys; tracer techniques; Tracers; Upstream; Waste Water Technology; wastewater; Water Management; Water Pollution Control; Water Quality/Water Pollution; Tunisia; MED, Tunisia; Salinization; Geochemical tracers; Coastal aquifers; Tunisia; Geophysical methods
• ISSN: 1431-2174; 1435-0157
• DOI: 10.1007/s10040-014-1180-7

The study area is a small coastal plain in north-eastern Tunisia. It is drained by an ephemeral stream network and is subject to several pollutant discharges such as oilfield brine coming from a neighboring oil company and wastewater from Somâa city, located in the upstream of the plain. Furthermore, a hydraulic head near the coastal part of the aquifer is below sea level, suggesting that seawater intrusion may occur. A time-domain electromagnetic (TDEM) survey, based on 28 soundings, was conducted in Wadi Al Ayn and Daroufa plains to delineate the saline groundwater. Based on longitudinal and transversal resistivity two-dimensional pseudosections calibrated with boring data, the extent of saline water was identified. Geochemical tracers were combined with the resistivity dataset to differentiate the origin of groundwater salinization. In the upstream part of the plain, the infiltration of oilfield brine through the sandy bed of Wadi Al Ayn seems to have a considerable effect on groundwater salinization. However, in the coastal part of the aquifer, groundwater salinization is due to seawater intrusion and the saltwater is reaching an inland extent around 1.3 km from the shoreline. The contribution ratios of saline water bodies derived from the inverted chloride data vary for the oilfield brine from 1 to 13 % and for the seawater from 2 to 21 %.