The origin of high sulfate concentrations and hydrochemistry of the Upper Miocene–Pliocene–Quaternary aquifer complex of Jifarah Plain, NW Libya
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Date
2016-10
Journal Title
Journal ISSN
Volume Title
Publisher
Springer-Verlag Berlin Heidelberg
Abstract
he high uncontrolled groundwater extraction in
Jifarah Plain, NW Libya, causes a modification of natural
flow systems, inducing seawater intrusion and causing
groundwater quality deterioration. The principal aim of this
study is to identify the hydrogeochemical processes in this
coastal aquifer in order to verify the main sources of sulfate
concentration increase that occurs in the system. In order to
achieve this aim, water samples were collected from 134
sampling wells in the study area and analyzed for the major
cations and anions; physical and chemical parameters were
measured, such as water level, electrical conductivity, pH and
temperature. The analytical results obtained in the hydro-
chemical study were interpreted using Piper diagram, ion
correlations with Na ? /Cl - , SO 42- , Cl - and TDS, in con-
junction with calculation of the ionic deviations of the con-
servative freshwater/seawater mixture and saturation indices
using the PHREEQC 2.16 software. The large SO 42-
anomaly observed in groundwater near the coast was
explained by the presence of seawater intrusion and upconing
of deep saline water in these areas. This conclusion is based on high chloride concentrations, the inverse cation exchange
reactions and the lower piezometric level compared to sea
level. Inland, in Sabratah, the high SO 42- values are related to
gypsum dissolution from the Upper Miocene Formation in
the lower part of the upper aquifer. These locally high SO 42-
concentrations in the south of the study area show overall
increase in the upstream direction, which also suggests the
dissolution of evaporites from the mountain aquifers in the
south. High SO 42- concentration is also related to the effect
of the scattered sebkha deposits in some areas along the coast.
Description
Journal Article
Keywords
Seawater intrusion, Overexploitation, Groundwater quality degradation, Gypsum dissolution, Sebkha, Upper aquifer, Tripoli