Adel Kharroubi

Assessment of sediment quality in the Mediterranean Sea-Boughrara lagoon exchange areas (southeastern Tunisia): GIS approach-based chemometric methods

Concentrations of selected heavy metals (Cd, Pb, Zn, Cu, Mn, and Fe) in surface sediments from 66 sites in both northern and eastern Mediterranean Sea–Boughrara lagoon exchange areas (southeastern Tunisia) were studied in order to understand current metal contamination due to the urbanization and economic development of nearby several coastal regions of the Gulf of Gabès. Multiple approaches were applied for the sediment quality assessment. These approaches were based on GIS coupled with chemometric methods (enrichment factors, geoaccumulation index, principal component analysis, and cluster analysis). Enrichment factors and principal component analysis revealed two distinct groups of metals. The first group corresponded to Fe and Mn derived from natural sources, and the second group contained Cd, Pb, Zn, and Cu originated from man-made sources. For these latter metals, cluster analysis showed two distinct distributions in the selected areas. They were attributed to temporal and spatial variations of contaminant sources input. The geoaccumulation index (Igeo) values explained that only Cd, Pb, and Cu can be considered as moderate to extreme pollutants in the studied sediments.

Anthropogenic and natural effects on the water and sediments qualities of costal lagoons: case of the Boughrara Lagoon (Southeast Tunisia)

The Boughrara Lagoon located in southern Tunisia shows evidence of eutrophication and the deterioration of water quality. The large amount of water shown to exchange tidally between the lagoon and the open sea suggests that while water per se is important and observed eutrophication problems are not caused by a lack of water. Heavy metal concentrations in surface sediments of the lagoon indicate that the ecosystem degradation is most likely related to the discharge of untreated phosphogypsum. Excessive pumping from the local freshwater aquifer that previously supplied freshwater to the lagoon via sub-aquatique fractures is likely to be a significant factor contributing to the water and sediment quality degradation of Boughrara Lagoon.

Groundwater chemistry and radon-222 distribution in Jerba Island, Tunisia

The present study integrates hydrogeological, hydrochemical and radiogenic data of groundwater samples taken from the Plio-Quaternary unconfined aquifer of Jerba Island, southeastern Tunisia, in order to interpret the spatial variations of the groundwater quality and identify the main hydrogeochemical factors responsible for the high ion concentrations and radon-222 content in the groundwater analysed. Thirty-nine groundwater samples were collected from open wells widespread on the island. Physical parameters (EC, pH, TDS and T °) were measured, major ions (Ca2+, Mg2+, Na+, K+, Cl-, SO42-, NO3- and HCO3-) were analysed and 222Rn concentrations were determined using a RAD7-H2O. Hydrogeochemical characterisation revealed that groundwater from the Jerba aquifer has several origins. Basically, two water types exist in the island. The first one, characterized by a low to moderate salinity with a chemical facies CaMgClSO4, characterizes the central part of Jerba (a recharge area) due to carbonate and gypsum dissolution. The second water type with high salinities, dominated by NaKCl type, was observed in coastal areas and some parts having low topographic and piezometric levels. These areas seem to be affected by the seawater intrusion process. The 222Rn concentrations in groundwater samples in Jerba varied from 0 Bq.L-1 to 2860 Bq.L-1 with an average of 867 Bq.L-1. The highest values were registered in the western coastal wells and near the fault of Guellala. However, the central and eastern wells showed low radon levels. Compared to 222Rn activity in some countries with the same lithology, radon concentrations in the Jerba unconfined aquifer have higher values influenced by the structure of the aquifer and by seawater inflow enriched with 222Rn resulting from the decay of uranium derived from phosphogypsum deposits in the gulf of Gabes. The EC and 222Rn spatial variability in the study area were mapped using ARC Map 10.3 software. Hydrochemical results in addition to geological data and radon activities confirm the existence of vertical communication between the Miocene aquifer and the unconfined Plio-Quaternary aquifer through fault system and a lateral communication with the sea via seawater intrusion.

Groundwater chemical and fecal contamination assessment of the Jerba unconfined aquifer, southeast of Tunisia

Located in the southeast of Tunisia, on the Mediterranean Sea, Jerba Island has a semiarid climate condition. The surface water scarcity has made groundwater the main source to supply the domestic, touristic, and agricultural water demand. Unconfined aquifer is a vulnerable costal aquifer system that undergoes several phenomena. This work aims at assessing the geochemical and bacteriological groundwater quality, defining groundwater pollution sources and promoting sustainable development and effective management of groundwater resources in Jerba Island. Data were collected after the wet season in 2014 from 79 wells. Electric conductivity, pH, TDS, and major and fecal tracers (total coliforms, thermotolerant coliforms, Escherichia coli, and Salmonella) were analyzed. Geochemical modeling including the relationships between geochemical tracers Na+ vs. Cl−, Ca2+ vs. Cl−, K+ vs. Cl−, representative ionic ratios (Br−/Cl−, Na+/Cl−, Mg2+/Ca2+), and statistical analysis were used to specify major process contributing to groundwater pollution and main factors controlling groundwater mineralization in the island. Groundwater varieties were hydrochemically classified into three types in terms of salinity values: group 1 (8.86%) to fresh water, group 2 (27.84%) to brackish water, and group 3 (63.29%) belongs to saline water. In addition, groundwater quality revealed high concentrations in chemical pollution tracers (Na+, Cl−, SO42−, and NO3−) and fecal tracers. Besides, most of the sampled wells were contaminated with nitrate (50.63%). Also, thermotolerant coliforms and E. coli were detected in all groundwater samples (96.2% of wells). Results indicated that the Jerba shallow aquifer was under serious threat from both natural and anthropogenic contamination. However, the wild discharge of domestic effluents, septic tanks, and sewage were the main origins of underground water contamination in Jerba Island. The reduction of fecal sources, through constructing normalized latrines is thus recommended.

Assessment of hot groundwater in an arid area in Tunisia using geochemical and fuzzy logic approaches

In this study, thermal groundwater from arid area in southeastern Tunisia was assessed for irrigation use. For this purpose, thirty-one water samples were collected and physiochemical parameters (EC, pH, TDS, major ions) were measured and analyzed. A fuzzy logic model was developed in which six parameters were integrated: electrical conductivity, sodium adsorption ratio, sodium percentage, Kelly ratio, permeability index and temperature. The membership functions for a fuzzy logic model were developed using linguistic terms and trapezoidal shapes. The fuzzy logic model developed was validated with a dataset of chemical analyses from groundwater sampled in the study area. The assessment indicated that 26% of the samples were in the “good” class, 10% in the “good to permissible” class, 55% are in the “permissible” class, 6% are in the “permissible to harmful” class and 3% were considered to be harmful and therefore unsuitable for use in irrigation. The effectiveness, simplicity and robustness of the fuzzy model assessment make this approach a more consistent and reliable way of assessing water quality than conventional methods of assessing water quality data.

Olive oil Mill Wastewater properties change during infiltration through clay soils

Olive oil Mill Wastewaters (OMW), are stored in clay basins in the region of Sfax (Tunisia). Field permeability measurements showed that the clay is not completely impermeable and its structure can be modified by the infiltration of OMW. Analysis of chemical composition of soil revealed the presence of phenolic compounds resulting from the percolation of OMW. An infiltration filled with clay and submerged with OMW at a height of 1.5 m was used to study the composition change of the support as OMW percolates through the clay. Compared to the raw OMW, infiltrated effluent showed a decease of its polluting load.

A Mamdani Adaptive Neural Fuzzy Inference System for Improvement of Groundwater Vulnerability: B. Agoubi et al. Groundwater x, no. x: x-xx

Assessing groundwater vulnerability is an important procedure for sustainable water management. Various methods have been developed for effective assessment of groundwater vulnerability and protection. However, each method has its own conditions of use and, in practice; it is difficult to return the same results for the same site. The research conceptualized and developed an improved DRASTIC method using Mamdani Adaptive Neural Fuzzy Inference System (M-ANFIS-DRASTIC). DRASTIC and M-ANFIS-DRASTIC were applied in the Jorf aquifer, southeastern Tunisia, and results were compared. Results confirm that M-ANFIS-DRASTIC combined with geostatistical tools is more powerful, generated more precise vulnerability classes with very low estimation variance. Fuzzy logic has a power to produce more realistic aquifer vulnerability assessments and introduces new ways of modeling in hydrogeology using natural human language expressed by logic rules.

Use of sediment quality indicators for heavy metals contamination and ecological risk assessment in urbanized coastal zones

The urbanized coastal zones are frequently faced to various pollutant discharges mainly in the shoreline. The quantification of the pollution level was mainly based on sea-water analysis. However, in this environment, the sediment characterization, using quality indicators, may constitute an accurate approach. The latter can be particularly appropriate to define heavy metals pollution degree. Chemical analyses of Cd, Cu, Zn, and Fe were undertaken for a total of 45 surface marine sediment samples of Gabes city coast. There is a significant extension of pollution, strongly influenced by the dominant longshore current. The studied sediments were found usually enriched with Cu, Cd, and Zn. These anthropogenic heavy metals have identical behavior and similar distribution. These metals did not show any correlations with Fe chosen as natural tracer. The multi-element indices used permitted to conclude that 70% of sampling sites are highly affected by heavy metal contamination and associated with very high ecological risk. These indices use a simple contamination factor, which, however, would not take account of the sedimentary inputs and the complex sediment behavior. Consequently, modified indices, employing enrichment factor, were used and demonstrated better to assess pollution and ecological risk.

Assessing the Groundwater Pollution Problem by Nitrate and Faecal Bacteria: Case of Djerba Unconfined Aquifer (Southeast Tunisia)

Djerba unconfined sandy aquifer (Southeast of Tunisia) is affected by several contamination phenomenon such as seawater intrusion and anthropogenic activities. This study aims to assess nitrate and faecal pollution in groundwater. More than 70 wells were sampled and analyzed. Geochemical assessment was used to understand the pollution origin and factors controlling this process in Djerba aquifer. Chemical and bacteriological analysis confirms that the sampled wells were seriously affected by both nitrate and faecal pollution problem. Chemical analysis shows that 51% of sampled wells have a nitrate levels more than 50 mg/l. The bacteriological results demonstrated that 95% of wells showed total coliforms densities higher than 10 CFU/100 ml. Thermotolerants coliforms and Escherichia coli were detected in all groundwater sampled (96% of wells). These results confirm the impact of anthropogenic activities on groundwater quality. It seems that this contamination is directly related to septic tanks, which are not waterproof; allow the infiltration of the major part of the liquid phase.