Moncef Gueddari

Geochemistry and quality assessment of groundwater using graphical and multivariate statistical methods. A case study: Grombalia phreatic aquifer (Northeastern Tunisia)

The Grombalia coastal aquifer, situated in Northeastern Tunisia, is a water source for public, agricultural, and industrial supplies in the region. The overexploitation of this aquifer, since 1959, and the agriculture activities led to the degradation, by places, of the water quality. The present study implemented graphical, modeling, and multivariate statistical tools to investigate natural and anthropogenic processes controlling Grombalia groundwater mineralization and water quality for promoting sustainable development. To attempt this goal, groundwater was collected from 33 observation wells in January 2004, and samples were analyzed for 10 physicochemical parameters (temperature, pH, salinity, Na+, Ca2+, K+, Mg2+, Cl−, HCO3−, and SO42−). Hydrochemical facies using Piper diagram indicates a predominance of a mixed facies, of the Na-Cl-HCO3 type, or Na-Ca-Cl-SO4 type, and, with less expansion, Na Cl type. The main factors controlling Grombalia groundwater mineralization seem to be mineral dissolution of highly soluble salts especially, the halite dissolution existing in the surface salty deposits and, with less importance, the ion exchange and reverse ion exchange process with clay minerals existing in the aquifer. The comparison of the major ions of the Grombalia groundwater, with the World Health Organization norms of potability (WHO 2004), reveals that these waters cannot be used for human consumption without any treatment. Most waters of the Grombalia aquifer, with a relatively high salinity, are not suitable for irrigation, in ordinary conditions. Nevertheless, they can be used for permeable soils, with an adequate drainage and applying an excess of leaching water.

Use of geographical information system and water quality index to assess groundwater quality in El Khairat deep aquifer (Enfidha, Central East Tunisia)

Groundwater is the most important natural resource used for drinking by many people around the world, especially in rural areas. In Tunisia, since the quantity and the quality of water available for different uses is variable from one place to another, groundwater quality in El Khairat deep aquifer was evaluated for its suitability for drinking purposes. To this end, an attempt has been made for the first time in order to determine spatial distribution of groundwater quality parameters and to identify places with the best quality for drinking within the study area based on: (1) an integrated analysis of physical–chemical parameters, (2) use of Geographical Information System, and (3) Water Quality Index (WQI) calculation. The physical–chemical results were compared with the World Health Organization (WHO) standards for drinking and public health, in order to have an overview of the present groundwater quality. According to the overall assessment of the basin, almost all the parameters analyzed are above the desirable limits of WHO. Using GIS contouring methods with Arcview 3.2a, spatial distribution maps of pH, TDS, EC, TH, Cl, HCO3, SO4, NO3, Ca, Mg, Na, and K have been created. The spatial analysis of groundwater quality patterns of the study area shows that the TDS value increases from north-west to south-east following the general trend of the Khairat aquifer flow direction. The spatial distribution map of TH shows that a majority of the groundwater samples falls in the very hard category. WQI was used to assess the suitability of groundwater from the study area for human consumption. From the WQI assessment, over 82% of the water samples fall within the “Poor” and “Very poor” categories, suggesting that groundwater from the south-eastern of the El Khairat deep aquifer is unsuitable for drinking purposes.

An integrated statistical methods and modelling mineral–water interaction to identifying hydrogeochemical processes in groundwater in Southern Tunisia

Abstract Groundwater is the most precious and valuable natural source of water in the southeast of Tunisia. The aim of this study is to find an adequate combination of methods for a qualitative description of geochemical processes into the Zeuss-Koutine, a Triassic and Miocene groundwater system, the unique source of water for this region of the Mediterranean (Medenine, Jerba, Zarzis and Jorf cities).Conventional classification techniques, statistical analyses and kriging methods were used to identify mineral processes distribution. This study finds that water chemistry is mainly dominated by dissolution/precipitation of minerals (calcite, dolomite, aragonite, anhydrite, gypsum and halite). Results obtained from principal component analyses (PCA) demonstrate that the variable responsible for water quality are largely related to soluble salts species (Na+, Cl-, Ca2+, Mg2+and SO42-). On the basis of the hierarchical cluster analysis (HCA), three groundwater clusters have been distinguished : cluster 1 is low TDS (<1000 mg L-1) Ca2+= Mg2+- Na+- SO42- waters which degrades into predominantly Na+-Ca2+-Cl--SO42- more saline groundwater (cluster 2) (TDS>3000 mg L-1) resulting from replacement of Ca by Na through cation exchange process on clay minerals. Cluster 3 is high TDS (>7000 mg L-1) NaCl waters from the aquifer system under confined conditions. Clusters 1 and 2 are located in preferential recharge zones whereas cluster 3 characterises downstream of the study area. Overall, a groundwater quality decrease has been observed similarly with a salinity increase from downstream to upstream towards the coast, where cation exchange processes and salinisation due to the long residence times appear to be the main processes responsible of more salty waters.

Major ion geochemistry of Ghannouch–Gabes coastline (at Southeast Tunisia, Mediterranean Sea): study of the impact of phosphogypsum discharges by geochemical modeling and statistical analysis

Since the 1970s, the Ghannouch–Gabes coastline (Southeast of Tunisia, Mediterranean Sea) has experienced significant industrialization, especially after the chemical industries were set up for phosphate ore processing in Ghannouch. These industries are the source of various discharges, phosphogypsum (PG) in particular, which is directly discharged into the sea, disastrously impacting the marine environment. The present study utilized geochemical modeling (PHREEQC) and multivariate statistical tools to identify and analyze the natural and anthropogenic factors governing the chemical composition of the major elements of the Ghannouch–Gabes coastal waters, especially through the study of the impact of the compounds derived from the PG discharge. To achieve this, a geochemical modeling and statistical investigation was conducted by dividing the study area into two zones: I and II. Zone I was located in the south of the study area, between the wadi Gabes and wadi al Fard. In Zone I, the water was less influenced by the PG inflow. The concentrations of the major elements, temperature values, pH, and dissolved oxygen content were comparable with those of the average surface seawater. Zone I water was supersaturated in terms of calcite and undersaturated with respect to gypsum and fluorite. Zone II, located in the north of the study area, between wadi Ettine and wadi Gabes showed water that was strongly influenced by the release of PG, with important amounts of Ca2+, SO42−, and F−. Application of the PHREEQC program showed that the PG released in this area was almost completely dissolved, a process accelerated by the high acidity and the high temperature of the water in this zone.

Groundwater hydro-geochemistry of Mateur Alluvial Aquifer (Northern Tunisia)

The sustainable management of the ground water resources of the Mateur alluvial aquifer (Northern Tunisia), which is threatened by salinization related to the infiltration of saline waters of Ichkeul lake in the discharge zone, is carried out by integrating, the geochemical data, presented in the form of GIS-based geochemical maps, the hydrogeochemical and the multivariate statistical methods, to understand the spatial and temporal vaiation of water mineralization and assign the major hydrochemical processes controlling its composition. Water samples were collected from 40 sites in wet and dry season, and analyzed for temperature, pH, salinity, dissolved oxygen, electrical conductivity and major ions. This study reveals that the origin of the groundwater mineralization was controlled by several coexisting processes, including : water origin (leaching of low mineralized water in the recharge zone and salt water into decharge zone), dilution in the wet season and evaporation in the dry season, thickness, grain size and lithology of the unsaturated zone. It’s noteworthy that the water-rock interaction does not contribute significantly to the solutes aquisition since minerals within aquifer are sparingly soluble. The spatial distribution maps of the major ions contents, especially Cl- and Na+, are similar with that of salinity, which increases down gradient. The principal component analysis (PCA), demonstrates that groundwaters are divided into two main groups: Moderately to weakly mineralized waters with Ca-Na-Cl and SO4 -Ca-Na-HCO3 -Cl facies, which are those of natural recharge area of the aquifer : Highly mineralized waters, with NaCl facies, characterizing the down Stream part, which is influenced by Salt water infiltration, from El Melah river, Ichkeul marshes and salty soils).

The effect of magnetic treatment on the physico-chemical and microbiological characteristics of hard waters

ABSTRACT The main objective of this study was to investigate the effect of magnetic treatment on the physico-chemical and bacteriological characteristics of hard waters. The scaling power of tested waters was evaluated using the rapid controlled precipitation (RCP) method. Results showed that magnetic treatment affects calcium carbonate crystallization. The RCP tests confirmed that the scaling power of the magnetically treated water was inhibited. Experimental results also indicated a significant improvement in the bacteriological quality of the treated water. Average reductions of 2.02 log Total coliforms, 0.95 log Escherichia coli and 1.06 log Faecal streptococci were obtained.

Assessment of the Trophic Status of the South Lagoon of Tunis (Tunisia, Mediterranean Sea): Geochemical and Statistical Approaches

The trophic status assessment of the South Lagoon of Tunis, a shallow Mediterranean coastal area after its restoration, is addressed herein with respect to its various environmental settings which are taken as indicators of water quality. The lagoon had, in the past, witnessed severe environmental quality issues. To resolve these problems, a large restoration project of the lagoon was undertaken which consisted of dredging the bottom sediments removing areas of water stagnation and improving water circulation. After this restoration work, the lagoon morphology has radically changed. In this paper, we attempt to evaluate the lagoon water’s trophic state to analyze the eutrophication risk after almost 16 years. In order to achieve these purposes, two water quality monitoring campaigns were conducted (July 2013 and February 2014). Natural and anthropogenic factors controlling the nutrient content of the lagoon water have been assessed through both geochemical methods and multivariate statistical tools. The results show that the nutrients are from external sources due to the discharge of municipal and industrial wastewater from the surrounding city of the catchment in the lagoon’s south side. According to the TRIX index, the lagoon remains eutrophic presenting a “poor” water quality, notwithstanding the engineering project due to the high level of nutrients.

Impact Assessment of Phosphogypsum Leachate on Groundwater of Sfax-Agareb (Southeast of Tunisia): Using Geochemical and Isotopic Investigation

The production of phosphoric acid by the Tunisian Chemical Group, in Sfax, Tunisia, led to the degradation of the groundwater quality of the Sfax-Agareb aquifer mainly by the phosphogypsum leachates infiltration. Spatiotemporal monitoring of the quality of groundwater was carried out by performing bimonthly sampling between October 2013 and October 2014. Samples culled in the current study were subject to physicochemical parameters measurements and analysis of the major elements, orthophosphates, fluorine, trace metals, and stable isotopes (18O, 2H). The obtained results show that the phosphogypsum leachates infiltration has a major effect on the downstream part of the aquifer, where the highest values of conductivity, , Ortho-P, and , and the lowest pH were recorded. In addition, these results indicated that phosphogypsum leachates contained much higher amount of Cr, Cd, Zn, Cu, Fe, and Al compared to the groundwater. Spatiotemporal variation of the conductivity and concentrations of major elements is linked to the phosphogypsum leachates infiltration as well as to a wide range of factors such as the natural conditions of feeding and the water residence time. Contents of and 2H showed that the water of the Sfax-Agareb aquifer undergoes a large scale evaporation process originated from recent rainfall.

Spatial and Temporal Variations of Water Quality of Mateur Aquifer (Northeastern Tunisia): Suitability for Irrigation and Drinking Purposes

The present study aims to assess the spatial and temporal variations of the hydrochemical characteristics of Mateur aquifer groundwaters, a crucial water resource in the northeast of Tunisia. The aquifer was subject to water quality deterioration due to salinization and nitrate contamination, and a new assessment of water quality was needed. For this purpose, 40 groundwater samples were collected during wet and dry seasons and analyzed for salinity, pH, T, O2, major cations and anions, and nutrient elements using standard methods and Water Quality Index (WQI). The results showed that most of the groundwater parameters were not within the permissible limits set by the World Health Organization in both seasons. The geochemical data were interpreted using WQI for drinking water. The spatial distribution maps of Water Quality Index showed that the highest quality was found, during both seasons, in the northwest and the southeast part of the aquifer, corresponding to the recharge zone, whereas the poor and very poor water quality was found in the outflow part of the aquifer. According to sodium adsorption ratio (SAR) and Na% values, most of the groundwater samples were not suitable for irrigation purposes and characterizing the eastern part of the aquifer and the outflow part of the aquifer, around the Ichkeul marshes.

A GIS mapping assessment of the suitability of the Oued Rmel aquifer for irrigation in the Zaghouan district (north-eastern Tunisia)

A total of twenty-three water samples were collected in winter 2013 to assess groundwater quality in the Oued Rmel aquifer in the Zaghouan governate in Tunisia. These samples were subject to in-field measurements of some physico-chemical parameters (temperature, pH, and salinity), and laboratory analysis of major elements. Several parameters were used to assess the quality of water destined for irrigation, including electrical conductivity (EC) and sodium adsorption ratio (SAR). As part of this work, GIS was used to study spatial distributions of SAR, EC, residual sodium carbonate, sodium percentage (%Na), Doneen’s permeability index, Kelly’s ratio, and magnesium hazard and, therefore, evaluated the water quality of Oued Rmel (good, fair, or poor) regarding irrigation. The major ions most abundantly found in the waters of Oued Rmel were in the following order: Na+ > Ca2+ > Mg2+ > K+ and Cl− > SO42− > HCO3. 56% of water samples from the Oued Rmel aquifer showed a low alkalinization risk, where SAR was lower than 10, 39% have a medium soil destabilization risks (10 < SAR < 18), and just 5% indicated high alkalinity hazards (SAR > 26). Samples of water intended for irrigation showed a medium to high sodicity and alkalinization risk. It is expected that output may help in assessing the impacts of water quality of the Oued Rmel aquifer used for irrigation.