In coastal Mediterranean regions the accumulation of contaminants in marine sediments is driven by the combined pressures of anthropogenic activities and environmental settings.This study investigates the influence of trace metals (TMs), total organic carbon (TOC), and nutrients, including total nitrogen (TN), from the El Kebir River on sediment quality in Tabarka's coastal ecosystem. In May 2024, we collected 24 surface sediment samples for geochemical and mineralogical analysis. The average concentrations of trace metals in the sediments were as follows: Fe (25,881 mg.kg(-)(1)), Cu (9.45 mg.kg(-)(1)), Zn (81.16 mg.kg(-)(1)), Pb (35.70 mg.kg(-)(1)), and Ni (44.45 mg.kg(-)(1)). Average TOC content was 0.93 % while TN was only detected at riverine stations ranging from 0.3 % to 0.52 %. Pollution indices including the Pollution Load Index (PLI = 0.66), Contamination Factor (CF) for Pb = 1.78 (moderate contamination), Geoaccumulation Index (Igeo), and the ecological Risk Index (RI) = 10.14 (low ecological risk), indicated that the area can be classified from unpolluted to moderately polluted. The TN/TOC ratio suggests a mixed origin of terrestrial and marine organic matter where higher values (0.12 - 0.15) are likely due anthropogenic TN inputs. The Pearson correlation coefficient (r) analysis reveals good positive correlations (r > + 0.5) between trace metals and organic matter (TOC, TN), emphasizing the anthropogenic nature of this contamination. Principal component analysis (PCA) revealed two dominant sources of contamination linked to wastewater discharge and rainwater drainage. While results suggest moderate contamination level, continued accumulation of trace metals and nutrients could alter ecosystem functioning and exacerbate long-term ecological degradation.These findings emphasize the apparent need for urgent measures to improve wastewater treatment and pollution control to protect the coastal environment of Tabarka.

Water erosion in Tunisian semi-arid regions causes harmful effects by silting reservoirs and reducing agricultural lands and soil fertility. Several factors are involved in the erosion process: rain erosivity, soil fragility, and degraded land cover on steep slopes associated with the intensification of inappropriate human practices. Thus, identifying erosion vulnerable sub-watersheds based on the assessed soil loss rate is very important to apply suitable conservation measures. The current research aimed to prioritize risky areas in the Lakhmess watershed, north-west Tunisia via the Soil Erosion Assessment using Geographical Information System (SEAGIS) model. To prioritize sub-watersheds vulnerable to soil erosion and sediment yield, the Lakhmess watershed, covering an area of 162 km2, was divided into 16 sub-watersheds (L1-L16), according to the hydrographic network. Then, the mean annual soil erosion rate and the mean annual sediment yield in the watershed were estimated by integrating the Revised Universal Soil Loss Equation (RUSLE) and the Sediment Delivery Ratio (SDR) in the SEAGIS model and their spatial distribution was determined. The obtained results indicate that the estimated average annual soil erosion rate is 4.2 t/ha/y and the annual sediment yield is 2.6 t/ha/y. Maner's SDR model was selected as the best model for estimating SY, with standard error, standard deviation, and coefficient of variation values of 0.75%, 0.01, and 0.45%, respectively. The prioritization of the Lakhmess sub-watersheds based on the estimated soil loss rate reveals that among the 16 sub-watersheds, three sub-watersheds (L10, L12, and L15) were identified as being in a very high priority soil erosion class. The high soil erosion rate and sediment yield in these subwatersheds is explained by the steep slope and a high rainfall erosivity factor. Six sub-watersheds (L2, L4, L5, L6, L7, and L16) were found to belong to a very low priority soil erosion class, as they are characterized by a very gentle slope, which appears to be an extremely determining factor. These findings constitute a basis for decision makers to plan effective conservation measures to conserve agricultural lands, soil, and water resources in northwestern Tunisia. (c) 2024 International Research and Training Centre on Erosion and Sedimentation. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd.

In Mediterranean coastal regions, the confluence of climate change and human activities withinwatersheds has led to an imbalance in nutrient and organic matter discharges, resulting in eutrophication and disruptions in marine ecosystems. This study examines the impact of nutrient inflows from coastal Rivers on marine environments and delineatesthe trophic dynamics of the Kelibia aquatic ecosystem in northeast Tunisia. From March to August 2020, 35 surface water samples were collected from both the downstream section of the Hajjar River and the coastal shallows of Kelibia. A comprehensive spatial-temporal monitoring initiative encompassedkeyparameters: dissolved oxygen (DO), chlorophyll biomass (Chl-alpha), dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), chemical oxygen demand (COD) and biological oxygen demand (BOD). Findings revealed pronounced concentrations of organic matter (COD> 100 mg O-2 L-1),elevated nutrient levels (NID >10 mg L-1; DIP > 50 mg L-1) and significant chlorophyll biomass (Chl-alpha > 500 mu g L-1) nearagri-food industry waste discharges.Additionally, dissolved oxygen levels in the downstream region of the Hajjar River werealarmingly low (DO < 2 mg L-1). The application of the TRIX eutrophication index indicated a trophic status shift, ranging from oligotrophic in March to mesotrophic in August. Given these persistent environmental challenges, proactive management strategiesare imperativeto address nutrient loading, mitigateeutrophication, and safeguardthe ecological functions and services of these delicate coastal ecosystems.

In Tunisia, water scarcity is only adding pressure on water demand in agriculture. In the context of sustainable development goals, Tunisia has been reusing treated wastewater (TWW) as a renewable and inexpensive source for soil fertigation and groundwater (GW) recharge. However, major risks can be expected when the irrigation water is of poor quality. This study aims for evaluating the potential risk of TWW and GW irrigation on soil parameters. Accordingly, we evaluated the suitability of water quality through the analysis of major and minor cations and anions, metallic trace elements (MTEs), and the sodium hazard by using the sodium adsorption ratio (SAR) and the soluble sodium percentage (SSP). The risk of soil sodicity was further assessed by SAR and the exchangeable sodium percentage (ESP). The degree of soil pollution caused by MTEs accumulation was evaluated using geoaccumulation index (Igeo) and pollution load index (PLI). Soil maps were generated using inverse spline interpolation in ArcGIS software. The results show that both water samples (i.e., TWW and GW) are suitable for soil irrigation in terms of salinity (electrical conductivity<7000 µS/cm) and sodicity (SAR<10.00; SSP<60.00%). However, the contents of PO43−, Cu2+, and Cd2+ exceed the maximum threshold values set by the national and other standards. Concerning the soil samples, the average levels of SAR and ESP are within the standards (SAR<13.00; ESP<15.00%). On the other hand, PLI results reveal moderate pollution in the plot irrigated with TWW and no to moderate pollution in the plot irrigated with GW Igeo results indicate that Cu2+ is the metallic trace element (MTE) with the highest risk of soil pollution in both plots (Igeo>5.00), followed by Ni2+ and Pb2+. Nevertheless, Cd2+ presents the lowest risk of soil pollution (Igeo<0.00). Statistical data indicates that Ca2+, Na+, Ni2+, and Pb2+ are highly distributed in both plots (coefficient of variation>50.0%). This study shows that the use of imagery tools, such as ArcGIS, can provide important information for evaluating the current status of soil fertility or pollution and for better managing soil irrigation with TWW.

Soil erosion is a natural phenomenon which causes many problems such as the reduction of soil fertility and silting of dams. In this study, the Cs-137 activities and the RUSLE model were used to quantify soil erosion rates in the Sgilil river watershed of northeastern Tunisia, and where 20% of the agricultural land is devoted to the cultivation of olive trees. In addition, the erosion dynamics and its spatial variation were inferred. The net erosion rates in the cultivated field based on the measured Cs-137 activities and using the Fallout Radionuclide Conversion Models range from 2.24 to 34.23 t ha(-1) yr(-1) when the Proportional Model is applied and from 1.49 to 30 t ha(-1) yr(-1) when the Mass Balance Model 2 is applied. The average erosion rates of the Sgilil river watershed estimated by the RUSLE model after multiplying five erosion factors for an average year (1990-2019) is 6 t ha(-1) yr(-1). Based on the RUSLE model results, around 52% of the watershed area falls within the slight erosion risk class (0-2 t ha(-1) yr(-1)) and 11% within the very severe erosion risk class (> 30 t ha(-1) yr(-1)). The center of the watershed, where the olive cultivated field is located belongs to a high to severe erosion risk class. Results attained through the isotopic approach and those found through the RUSLE modeling are in agreement.

In this study, the total concentrations and chemical forms of heavy metals (Fe, Zn, Pb, Cu, Cr, Cd, and Ni) in surface sediments of the South Lagoon of Tunis located in northeast Tunisia were investigated. Multiple geochemical indices were applied to assess the potential environmental risks. The South Lagoon is a valuable regional resource for fisheries, tourism and aquaculture. Total metal concentrations exhibited significant spatial variation attributed to the principal water circulation direction (east to west). The chemical speciation of Fe, Cr and Ni shows that they were mostly related to the residual fraction (Fe 34.8%, Cr 37.4% and Ni 37.9%), while Pb, Zn, Cu, and Cd were mostly related to the non-residual fraction (labile fraction Pb 89.4%, Zn 26.1%, Cu 71.8% and Cd 84.3%). Pb, Zn, Cu and Cr are of high potential bioavailability. The highest pollution was found on the west side of the lagoon according to the calculated global contamination factors. Besides, individual contamination factors, Pb followed by Zn and Cu, posed the highest risk of contamination. This study shows that, even after dredging, the persistence of low concentrations of some contaminants may cause environmental problems in certain physico-chemical conditions.

The Meliane River, the second longest and most important river in Tunisia, is one of the major rivers that flow into the Gulf of Tunis. However, it is known by its significant discharges of urban and industrial activities that have seriously affected the quality of the aquatic ecosystem. The highest amounts of Cadmium (Cd), Copper (Cu), Lead (Pb), Zinc (Zn), Nickel (Ni), Chromium (Cr) and Manganese (Mn) in the surface sediments of the Meliane River indicate that the downstream part is the most polluted area. The chemical speciation shows that the majority of the trace metals are bound to a reducible fraction (Zn, Mn, Cr and Ni) and the Pb and Cu are bound to the oxidizable fraction. The Cd is linked to the exchangeable fraction, which indicates its high mobility and toxicity. Both the contamination and enrichment factors values of some trace metals are elevated in the downstream part of the Meliane River. The percentage of the risk assessment code in Cd is 59.8%, which presents a very high environmental risk. Therefore, the spatial distribution of trace elements in the surface sediments is characterized by its high concentration of metals in the downstream part of the Meliane River. These concentrations decrease as a function of change in the physicochemical parameters from the freshwater-saltwater mixing zone to marine stations.

The Mateur multi-aquifer system, consisting of a Quaternary alluvial aquifer and a Campanian limestone aquifer, is one of the most significant aquifer systems in northern Tunisia providing domestic and agricultural water supply for the entire Mateur region. The present study aims to unveil the various factors and mechanisms controlling the groundwater chemistry of such system. Indeed, integrated hydrogeochemical and isotopic approaches are used herein to identify the alluvial and limestone aquifer waters mixing and evolution in the Mateur region. Results show that despite the difference in aquifer lithology, there is little difference in the major ion geochemistry and stable isotope ratios of groundwater within the Mateur plain. Waters from the Quaternary alluvial aquifer are classified into two predominant facies: mixed facies (Ca-Na-SO4-Cl and Ca-Na-HCO3-Cl) and Na-Cl facies. Similarly, waters from the limestone aquifer have also mixed facies (Ca-Na-SO4-Cl) and sodium chloride facies (NaCl). Groundwater delta O-18 and delta H-2 values show more homogeneous values along the groundwater flow direction, indicating inter-aquifer mixing processes. Tritium contents of the Campanian aquifer are lower than those of the Quaternary aquifer, indicating a relatively older age or mixture with recent waters. This validates a concept of the hydraulic continuity between the Quaternary aquifer and the Campanian aquifer which is consistent with the geochemical analytical results.

Water pollution o by agricultural and human activities has become a hot topic that must be taken into account. Its qualitative and quantitative evaluation has been well demonstrated by the SWAT model. The proposed research is an important step in the study of the agricultural and human pollution, in the various tributaries of Sidi Salem dam. We envisaged the use of the tool SWAT, for one of the main polluting tributaries, Wadi Beja, and planned a qualitative management of this watershed. The application of this model requires a prior study of the hydrological basin of interest and the calibration of a large number of intrinsic factors specific to the area of study. This model has been mainly tested on several watersheds in the Nordic countries, including Canada and France because the model contains a module specific to the glacial melt. Its adaptation to the Mediterranean context has rarely been carried out. In the case of Tunisia, the absence of a long ongoing series of measurement data and hydrodynamics of the soil hampers the application of the SWAT model. In a first step, we adapted this model to the specific context of the study area, in order to understand the hydrological functioning of this watershed. Subsequently, we studied the sensitivity of the model according to the key hydrological parameters, by performing the continuous simulation for more than 8 years. This allowed us to have a better choice of the shimming parameters, in order to properly shim the model. In a second step, we refined the model calibration settings according to 2 years of deep study: wet and dry, though opting for a seasonal cutting for the sake of better describing the pedoclimatic context of the study area. This approach should have a good match of the simulated and observed data, as confirmed by four accuracy measures. In addition, it has been shown that the contents of nitrate and orthophosphate were of concern because of the poor use of agricultural fertilizers. Of this fact, various scenarios of management have been developed and tested by the model in order to reduce the percolation rate of various forms of nitrogen and t phosphorus leaching. These approaches would enable policymakers to monitor the water pollution in the dam area while reducing the burden of various eutrophying elements.

Water erosion in Tunisia is influenced by climatic irregularity and torrential flows, caused the loss and fragility of soil and the reduction of dam life. To fight against this scourge, Tunisia has adopted national strategies for water and soil conservation, in particular anti-erosive measures such as banks and mountain lakes. The objective of this study was the modeling of water erosion by the SEAGIS model (Soil Erosion Assessment using GIS) in Rmel watershed which covers an area of 680 km2 subdivided into six sub-watersheds (RM1–RM6), according to the hydrographic network, which allows to spatialize the risks of soil erosion and to quantify the annual sediment yield in the Rmel dam. The result attain demonstrate that the average annual soil erosion was 26.74 t ha−1 yr−1 estimated by incorporating the revised universal soil loss equation (RUSLE) into the SEAGIS model. The means annual sediment yield by SEAGIS is 14.92 t ha−1 yr−1. The results in dry year, for soil erosion and solid charge are, respectively, 11.76 t ha−1 yr−1 and 6.41 t ha−1 yr−1 and during wet year, 79.15 t ha−1 yr−1 and 43.43 t ha−1 yr−1 show that the factor has a great effect on soil erosion is atmospheric precipitation. Thus these results are able to simulate the quantity of the solid charge transferred to a dam and constitute a database to fight against soil erosion and ensure sustainable agriculture in north-eastern Tunisia.

Like most North African countries, Tunisia is characterized by a harsh arid and semi-arid climate with scarce water resources and poor water quality on most of its territory. The quality of groundwater is not immune to pollution. Sminja aquifer, located in Zaghouan district in Northeastern Tunisia, has been used to meet Zaghouan agglomeration needs for drinking purposes and irrigation uses. On the other hand, the region has suffered from inefficient usage and mismanagement of water resource due to appropriate legal, political, and economic frameworks to take into consideration the regional vulnerability to climate change and population growth. The application of the Susceptibility Index (SI) makes it possible to evaluate the impact of agricultural activities on the water quality in Sminja aquifer, using five parameters [depth of water (D), net recharge (R), aquifer media (A), topography (T) and Land use (LU)]. Modular three-dimensional multispecies transport model was used to assess, simulate and predict pollution transport of nitrate. The vulnerability index's spatial distribution shows that the most vulnerable area was found in the extreme north of the Sminja aquifer. It shows that a high vulnerability characterizes 21% of the study area (70 < SI < 60). The moderate to high vulnerability areas to pollution occupied 12% of the aquifer and the moderate to low vulnerability zones occupied 67% of the total area. The outputs of the SI reflect a good correlation with the measured nitrate concentrations. After calibration completion, the MT3DMS transport model results showed a good correlation between measured and simulated nitrate concentrations. The predict scenarios show that the nitrate propagates in all the aquifer, from the irrigated area to the non-irrigated area.

MEDSAL is a research project (www.medsal.net) focusing on groundwater salinization in the Mediterranean area, funded by the PRIMA Program (Partnership for Research and Innovation in the Mediterranean Area), and running for 36 months starting from September 2019. MEDSAL constitutes a joint Euro-Mediterranean cooperation network of organizations from Mediterranean countries and associated states of the EU contributing national funds. The partnership involves eight academic partners from seven countries (plus an external collaborator – private firm), covering a wide range of academic experts in various scientific fields (e.g. hydrogeology, hydrogeochemistry, environmental isotopes, modeling, hydro-informatics, geostatistics, machine learning). MEDSAL aims at developing innovative methods to identify various sources and processes of salinization and at providing an integrated set of modeling tools that capture the dynamics and risks of salinization. Thereby, it aims to secure the availability and quality of groundwater reserves in Mediterranean coastal areas, which are amongst the most vulnerable regions in the world to water scarcity and quality degradation. MEDSAL encompasses six (6) test sites located in five (5) countries: Rhodope, Greece, (ii) Samos Island, Greece, (iii) Salento, Italy, (iv) Tarsus, Turkey, (v) Boufichia, Tunisia, and (vi) Bouteldja, Algeria. MEDSAL’s principal objectives are the following: a) Deliver new tools for the identification of complex salinization sources and processes, b) Exploit the potential of Artificial intelligence and Deep Learning methods to improve detection of patterns in multi-dimensional hydrogeochemical and isotope data, c) Elaborate tailor-made risk assessment and development of management plans by coupling salinization forecasts with climate change impacts and future scenarios, and d) Develop a public domain web-GIS Observatory for monitoring, alerting, decision support and management of coastal groundwater reserves around the Mediterranean. MEDSAL is expected to have a significant impact on water resources availability and quality by improving the identification and development of adequate strategies and measures for the protection and management of salinization in coastal aquifers. In this context, MEDSAL will provide innovative classification and detection methods of groundwater salinization types for Mediterranean coasts, also in complex karstic and data-scarce environments. These outcomes will be reached by better integration of hydrogeochemical and environmental isotope data with physical-based groundwater flow and transport models and advanced geostatistics. Artificial intelligence and deep learning methods will be also used to improve the detection of patterns in multi-dimensional hydrogeochemical and isotope data.

In Tunisia, chemical industries are thought to be the cause of various environmental problems and more particularly the cause of groundwater quality deterioration and contamination. Within this scope, this study assesses the shallow-water quality of the Gabes-North aquifer with regard to the phosphate industry and also to model current and possible future contamination. This allows also the identification of factors that govern the spatial–temporal variation of the main sources of pollution. For that, 60 shallow groundwater samples were collected during the years 2013 and 2014 within and around the industrial chemical phosphate complex of Ghannouche–Gabes. Hydrogeochemical investigation permitted the detection of high concentrations of fluoride and orthophosphates in the sampled waters reaching 12 mg/l and 47 mg/l, respectively. The H2PO4− and F− ion transport model using the Visual MODFLOW software was calibrated and validated by the 2013 and 2014 observed data and was simulated for 6205 days up to the year 2030. The model showed that from 365 to 6205 days, the ions H2PO4− and F− migrated from 100 to 250 m and from 80 to 200 m, respectively, depending on groundwater flow direction. Predictive simulations indicate that the transport rate of these ions can go up to 2.5 times in 2030 compared to those detected in 2014. This integrated investigation in this current study proves that regular pollution constitutes a threat at a given local scale, but can also be used as a reference for reasonable water resources management on a larger scale.

The study of water quality and the quantification of reserves and their variations according to natural and anthropogenic forcing is necessary to establish an adequate management plan for groundwater resources. For this purpose, a modeling approach is a useful tool that allows, after calibration phase and verification of simulation, and under different scenarios of forcing and operational changes, to estimate and control the groundwater quantity and quality. The main objective of this study is to collect all available data in a model that simulates the Jeffara of Medenine coastal aquifer system functioning. To achieve this goal, a conceptual model was constructed based on previous studies and hydrogeological investigations. The regional groundwater numerical flow model for the Jeffara aquifer was developed using MODFLOW working under steady-state and transient conditions. Groundwater elevations measured from the piezometric wells distributed throughout the study area in 1973 were selected as the target water levels for steady state (head) model calibration. A transient simulation was undertaken for the 42 years from 1973 to 2015. The historical transient model calibration was satisfactory, consistent with the continuous piezometric decline in response to the increase in groundwater abstraction. The developed numerical model was used to study the system's behavior over the next 35 years under various constraints. Two scenarios for potential groundwater extraction for the period 2015-2050 are presented. The predictive simulations show the effect of the increase of the exploitation on the piezometric levels. To study the phenomenon of salinization, which is one of the most severe and widespread groundwater contamination problems, especially in coastal regions, a solute transport model has been constructed by using MT3DMS software coupled with the groundwater flow model. The best calibration results are obtained when the connection with the overlying superficial aquifer is considered suggesting that groundwater contamination originates from this aquifer. Recommendations for water resource managers The results of this study show that Groundwater resources of Jeffara of Medenine coastal aquifer in Tunisia are under immense pressure from multiple stresses. The water resources manager must consider the impact of economic and demographic development in groundwater management to avoid the intrusion of saline water. The results obtained presented some reference information that can serve as a basis for water resources planning. The model runs to provide information that managers can use to regulate and adequately control the Jeffara of Medenine water resources.

The Oued Rmel aquifer, in Zaghouan city in north-eastern Tunisia, extends geographically between 36°18′ and 36°26′ North, and between 10°06′ and 10°24′ East. The groundwater of the Oued Rmel aquifer is exploited for drinking and irrigation purposes. To monitor the chemical water quality, and especially to identify the occurrence and behaviour of fluoride, 23 water samples were collected in January 2013, and analysed for chemicals parameters such as Na+, Ca2+, Mg2+, K+, Cl−, SO42−, HCO3− and F−. This study applied conventional techniques such as hydrochemical compositions, multivariate statistical methods, Geochemical Modeling and Geographical Information Systems (GIS). Concentrations of fluoride in samples from the Oued Rmel aquifer ranged from 4 to 22 mg/L. The highest values were observed in the surroundings of hydrothermal sources, especially from Hammam Zriba and Hammam Djedidi. Compared with international and national guidelines, all analysed samples exceeded the maximum permissible concentration, in drinking water, of WHO and Tunisian Standards (NT.09.14), which are 1.5 and 1.2 mg/L, respectively. Consequently, up to 75% of the population in the region who use groundwater as a source of drinking water are at risk of developing dental or skeletal fluorosis. Thus, the treatment of fluoridated water through methods such as precipitation, ion exchange, electrodialysis, and reverse osmosis is essential.

The Tunisian coast is suffering from several active or abandoned polluted sites, suspected to have released high concentrations of various contaminants infiltrating the environment and probably causing groundwater degradation. Within this scope, this study comes to assess and model the Sfax-Agareb aquifer contamination by fluoride released through phosphogypsum leachate percolation. For that, a spatial-temporal monitoring of fluoride contents was achieved for the period between October 2013 and October 2014. Observed data show that hazardous water contamination is occurring especially close to the phosphogypsum leachate collection basins. At this level, groundwater fluoride concentrations may reach up to 29 mg/L. Flow and transport modeling to evaluate fluoride contamination plume expansion in 2030 was achieved using MODFLOW and MT3DMS software packages based on a homogeneous and isotropic aquifer conceptual model. Flow and transport model calibrations were assessed by varying hydraulic conductivity, effective porosity, and dispersivity and then validated through observed data for two reference dates (October 2013 and October 2014). Based on the Tunisian NT 106-002 liquid discharge norms, fluoride contamination front was set at 3 mg/L. Numerical simulation shows that, in 2014, plume contamination by fluoride in the saturated zone extended over 250 m from the contamination source. In 2030, the spatial extent of this contamination will extend over a distance of 900 m towards the sea, following the aquifer flow direction. At the control piezometer, fluoride concentrations will increase from 29 mg/L in 2014 to 86 mg/L in 2030. This study, using numerical modeling, gives new insights for short- and medium-term prediction of eventual fluoride concentrations in the saturated zone of the Sfax-Agareb aquifer.

Soil organic matter has generated international interest in carbon and nitrogen sequestration. In reality, small fluctuations of soil organic stock could have large impacts on global warming. Therefore, quantification of Soil Organic Carbon (SOCs) and Total Nitrogen (TNs) stocks in surface and deep horizons are important to control the release of greenhouse gases. The present research was undertaken in order to determine SOCs and TNs evolution over 50 years. For this aim, we selected two soils (P1 and P2) developed under contrasted pedogenetic conditions in North-West of Tunisia (Beja governorate). P1 is a Luvisol located in a forest region. However, P2 is a Cambisol situated in an agriculture zone. Soil samples were gathered from surface (0-30 cm) and deep (50-100 cm) horizons in 1971, 2005, 2012 and 2019. SOCs declined in surface and deep horizons during the experimental period in both studied soils. In the case of Luvisol, the values declined from 91.01 t/ha to 75.54 t/ha and from 53.00 t/ha to 24.51 t/ha, respectively in surface horizons and deep horizons. Likewise, the SOCs values decreased from 84.24 t/ha to 25.52 t/ha in surface horizons and from 24.45 t/ha to 14.20 t/ha in deep horizons of the Cambisol. The TNs recorded lower values than SOCs. Nevertheless, they showed the same behavior. Our results showed that the highest values of SOCs and TNs were recorded in the Luvisol. This soil exhibited the greatest amount of organic matter since it was developed under forest vegetation. In addition, the results showed an enrichment in SOCs and TNs of superficial horizons to the detriment of the deep horizons. Nevertheless, this decrease in organic stocks with depth occurred following different patterns according to soil type. In fact, the Cambisol reported an important depletion of soil organic stocks as compared to the Luvisol. The loss of SOCs and TNs were estimated to be 69.71% and 54.17% in surface horizon, and 41.94 % and 28.28 % in deep horizon, respectively. Indeed, the land-use change increases the decomposition of soil organic matter principal source of SOCs and TNs. Such a reduction has wider implications on global warming and soil fertility.

In Tunisia, Groundwater is an important water source for domestic, agricultural and industrial uses, but the deterioration of its quality, under the influence of anthropogenic activities and natural factors, limits its suitability for human consumption and irrigation. The present study was carried out to assess groundwater quality in Bouficha aquifer in north-eastern Tunisia using geochemical, geospatial and statistical techniques. The relationship between groundwater quality and Land Use Land Cover (LULC) patterns were also explored using remote sensing, geographic information system (GIS) and Landsat satellite images. Groundwater samples were collected from sixteen wells in April 2015 and analyzed for their physical and chemical characteristics. Concentrations of major cations and anions in the groundwater vary spatially. The dominant water types in the investigation area are Na-Cl and Ca–SO4. A basic statistical study, applying hierarchical classification analysis confirms the existence of two groundwater types. To evaluate the suitability of groundwater for irrigation, chemical data were assessed using methods such as Electrical Conductivity, Kelley’s ratio, Sodium Absorption Ratio, Magnesium Hazards, as well as Residual Sodium Carbonate. Regarding drinking groundwater assessment, the World Health Organization (WHO) standards were applied to define sites with drinking water permissible levels. Information was loaded in an ArcGIS software and analyzed with a Spatial Analyst extension using Inverse Spline interpolation methods. Fluoride content in most samples has values as high as 1.97 mg/L, with 53% of the samples showing fluoride concentration higher than the level suggested by the WHO for drinking water of 1.5 mg/L and ratified by the National Society of Exploitation and Drinking Potable Water of Tunisia. Additionally, reported nitrate concentrations are higher than the expected groundwater background level of 10 mg/L; indeed, values are up to 286 mg/L, being hazardous for domestic use and suggesting the presence of anthropogenic sources of water contamination. The Land Use and Land Cover (LULCC) of Bouficha aquifer were changed over seventeen years. The Landsat satellite images have shown that the built-up area increased from 2001 to 2018 to the detriment of water and crop vegetation. The overuse of fertilizers on a total agricultural area of Bouficha aquifer (60%) led to significant pollutants, including nitrate and a deterioration in its water quality. Regarding the WHO and the Tunisian drinking water guidelines, this work provides substantial evidence that groundwater quality is posing a significant health threat for residents. Similarly, results show groundwater’s chemical content is also unsuitable for economic activities in the Bouficha region, mainly hazardous for irrigation purposes.