A research has been carried out to investigate the effects of below sea level mining on the cemen... more A research has been carried out to investigate the effects of below sea level mining on the cement raw material quality of a limestone quarry located adjacent to the shoreline near Darica-Kocaeli-Turkey. Field studies involved rock mass characterization through discontinuity surveys performed at the working benches of the quarry as well as on the core samples, monitoring of groundwater levels, performance of water pressure tests, and in-situ hydrochemical measurements. Hydrogeological data suggest that the carbonate sequence forms a poor unconfined aquifer having hydraulic conductivity values ranging between 10 À6 m/s and 10 À8 m/s. In the quarry, water seepages can only be observed at the shear zones. Electrical conductivity profiles taken from the boreholes located at various distances from the shore line indicated the present position of the salt water wedge.
HAL (Le Centre pour la Communication Scientifique Directe), 2013
Niger is the largest nation in West Africa (with 1.26 million km2), located between the Sahara an... more Niger is the largest nation in West Africa (with 1.26 million km2), located between the Sahara and sub- Saharan regions without coast line. The majority of the country is covered by desert. Low precipitation (151 mm per year in 2009, World Bank 2010) and recurring droughts have made groundwater an essential water source. In the Diffa region (ca. 150 000 km2), located in south-eastern Niger and in the north-west of Lake Chad, groundwater is an important water source for the local population, together with surface water from Lake Chad and less importantly from the Komadougou Yobe River. A decreasing trend in rainfall, and hence shrinking of the area around Lake Chad, and irrigation development proposed by Nigerian authorities to meet growing food demand have led to actual and potential increases in groundwater exploitation. Moreover, water from Lake Chad has high salt content, limiting its usage. Groundwater resources in the region are found in several aquifer systems: (a) the Manga Quaternary aquifer covering nearly the entire Diffa region at 20 m to more than 50 m depth, except in a central part of the region (less than 10 m depth); (b) the alluvial aquifer located in the Komadougou valley and in topographic depressions of the region at a shallow depth (less than 10 m); (c) the Pliocene aquifer in the Pliocene sands and silts, covering the entire region at about 300 m depth in most of the region or at about 200 m in the central part; (d) the Continental Intercalary/Hamadien aquifer, covering the entire region at 40 to 60 m depth with a very low or zero recharge rate. To improve groundwater resource use and management of the potable water supply in the Diffa region, Technical Cooperation project NER8011 was conducted from 2009- 2012 to characterize the Manga Quaternary aquifer system. The project was entitled Studying the Recharge Process and the Status of Mineral Deposits Within the Manga Aquifer (Diffa region). The project was implemented by le Ministere de L'Hydraulique et de l'Environnement, Direction des Ressources en Eau of Niger
The assessment of nitrate pollution origin using stable isotope techniques is a fundamental prere... more The assessment of nitrate pollution origin using stable isotope techniques is a fundamental prerequisite for the application of sustainable groundwater management plans. Although nitrate pollution is a worldwide groundwater quality problem, existing knowledge on the origin of nitrate pollution in arid and semi-arid regions is still scarce. Using the example of the Grombalia aquifer (NE Tunisia), this work summarizes the main strengths and constraints of multi-isotope techniques targeting at nitrate source identification and apportionment The results highlighted that, even in the case of well-established methodologies, like those of isotope hydrogeochemistry (δ15NNO3, δ 18ONO3 and δ 11B) and mixing modelling for source apportionment, it is fundamental to take into account regional and local end-members to avoid biased data interpretation and to fully exploit the potential of such accurate tools.
Nitrate contamination still remains one of the main groundwater quality issues in several aquifer... more Nitrate contamination still remains one of the main groundwater quality issues in several aquifers worldwide, despite the perduring efforts of the international scientific community to effectively tackle this problem. The classical hydrogeological and isotopic investigations are obviously of paramount importance for the characterization of contaminant sources, but are clearly not sufficient for the correct and long-term protection of groundwater resources. This paper aims at demonstrating the effectiveness of the socio-hydrogeological approach as the best tool to tackle groundwater quality issues, while contributing bridging the gap between science and society. An integrated survey, including land use, hydrochemical (physicochemical parameters and major ions) and isotopic (d 15 NNO3 and d 18 ONO3) analyses, coupled to capacity building and participatory activities was carried out to correctly attribute the nitrate origin in groundwater from the Grombalia Basin (North Tunisia), a region where only synthetic fertilizers have been generally identified as the main source of such pollution. Results demonstrates that the basin is characterized by high nitrate concentrations, often exceeding the statutory limits for drinking water, in both the shallow and deep aquifers, whereas sources are associated to both agricultural and urban activities. The public participation of local actors proved to be a fundamental element for the development of the hydrogeological investigation, as it permitted to obtain relevant information to support data interpretation, and eventually guaranteed the correct assessment of contaminant sources in the studied area. In addition, such activity, if adequately transferred to regulators, will ensure the effective adoption of management practices based on the research outcomes and tailored on the real needs of the local population, proving the added value to include it in any integrated investigation.
... by northeast-southwest fold belts bordered by fault corridor systems and separated by basins ... more ... by northeast-southwest fold belts bordered by fault corridor systems and separated by basins filled with Mio???Plio???Quaternary deposits (Burollet 1956; Khessibi 1978; Ben Ayed 1986; Boukadi 1994; B??dir 1995; Chekhma 1996; Ben youssef 1999 ... Hamdi Neji ... Md B Hassen W.20 ...
Patterns and Mechanisms of Climate, Paleoclimate and Paleoenvironmental Changes from Low-Latitude Regions, 2019
In the present context of climate change and increasing demand for water, it is crucial to identi... more In the present context of climate change and increasing demand for water, it is crucial to identify the origin, groundwater flow dynamics and mean residence times for sustainable management of water resources. In this study, groundwater residence time and recharge conditions of the deep aquifer of Sfax were investigated using environmental isotopes and noble gases. The results show that Sfax deep groundwater was recharged during cooler period of Late Pleistocene. In broad agreement with evidence from other paleoclimate investigations, the estimated noble gas recharge temperature (NGT) is lower than the present by about 5.5 °C. Oxygen isotopes values of Late Pleistocene are also 1.5‰ lower than modern precipitation.
Abstract The Complex Terminal Aquifer in Kebili basin (CTAK) is one of the most important deep gr... more Abstract The Complex Terminal Aquifer in Kebili basin (CTAK) is one of the most important deep groundwater reserves in the North West Aquifer Sahara System (NWASS). It plays a crucial role in the regional socio-economic development as it represents the main source of water supply in the region. However, the exploitation increases given rise to a grave water quality degradation and a gradual hydraulic head lowering. Using geostatistical and modelling methods and geochemical tools, this investigation aims to: (i) improve the understanding of hydrogeological structure of the aquifer through more precise maps; (ii) evaluate the quality of the CTAK groundwater and their compliance with international standards; (iii) develop an integrated hydrogeological conceptual model able to describe the hydrodynamic functioning of the aquifer. The calculated recharge and flow rates, using carbon 14 activities, are very low confirming the long residence time of CTAK groundwater. The use of quality indicators proves that 51% of the groundwater samples show poor quality for drinking purposes. In terms of agricultural activities, only 6% of waters are good to permissible for irrigation purposes, while 44% are doubtful for use. Based on this multidisciplinary analysis, the established hydrogeological conceptual model will provide a required basis for futures numerical groundwater flow models used in the management strategies under these conditions.
Major element concentrations and stable (δ18O and δ2H) and radiogenic (3H and 14C) isotopes in gr... more Major element concentrations and stable (δ18O and δ2H) and radiogenic (3H and 14C) isotopes in groundwater have proved useful tracers for understanding the geochemical processes that control groundwater mineralization and for identifying recharge sources in the semi-arid region of Sfax (southeastern Tunisia). Major-ion chemical data indicate that the origins of the salinity in the groundwater are the water–rock interactions, mainly the dissolution of evaporitic minerals, as well as the cation exchange with clay minerals. The δ18O and δ2H relationships suggest variations in groundwater recharge mechanisms. Strong evaporation during recharge with limited rapid water infiltration is evident in the groundwater of the intermediate aquifer. The mixing with old groundwater in some areas explains the low stable isotope values of some groundwater samples. Groundwaters from the intermediate aquifer are classified into two main water types: Ca-Na-SO4 and Ca-Na-Cl-SO4. The high nitrate concentr...
In a semi-arid to arid climate region, socio-economic development is mainly dependent on deep gro... more In a semi-arid to arid climate region, socio-economic development is mainly dependent on deep groundwater resources. This is the case of the Continental Intercalaire (CI) groundwater which is one of the most important aquifers in the North Western Sahara in Africa. This aquifer system, extending over more than a million of km2, is mainly confined, poorly recharged but intensely abstracted in Southern Tunisia. Efficient management of this resource relies on accurate data such as recharge/discharge rate and groundwater dynamics. In this study, environmental isotopes (2H, 18O, 13C, and 14C) were combined with long time lived radio-nuclide (81Kr) to give greater constraint on the groundwater residence time in the CI. Stable isotope signature is depleted compared to the modern rainwater of Sfax station with very low deuterium excess suggesting a paleoclimatic effect. This finding is strongly supported by 14C measurements where most of the analyzed samples are below the detection limit. T...
Groundwater is the major source of water supply in many rural and urban areas located within the ... more Groundwater is the major source of water supply in many rural and urban areas located within the Volta river basin in Benin [1] (Fig.1). This river basin is located in the Sudano-Sahelian zone, which is characterized by a contrasting geomorphology of hill chains extending from the East to the Center, and a lowland in its western part. The mean annual rainfall and potential evapotranspiration is 1173 mm and 1494 mm, respectively [2]. In the West, the sedimentary sequences are monoclinic and comprise the sedimentary basin of Pendjari. They become gradually folded towards the East [3]. Four geological sub-units can be distinguished within the studied area, namely (from West to East): the Pendjari sedimentary basin, Buem, Atacora and the basement s.s. formation. The northern area is occupied by the Pendjari National Park surrounded by rural areas where intensive population growth occurs . A better assessment of groundwater resources in this area is a strategic point for the sustainable ...
Groundwater resources are facing increasing pressure especially in semi-arid regions where they o... more Groundwater resources are facing increasing pressure especially in semi-arid regions where they often represent the main freshwater resource to sustain human needs. Several aquifers in the Mediterranean basin suffer from salinization and quality degradation. This study provides an assessment of Grombalia coastal aquifer (Tunisia) based on multidisciplinary approach that combines chemical and isotopic (δ2H, δ18O, 3H, 14C and δ13C) methods to characterize the relation between groundwater quality variation and aquifer recharge. The results indicate that total dissolved solids exceed 1000 mg/L in the most of samples excepting the recharge area. In addition to water–rock interaction, evaporation and nitrate pollution contributing to groundwater mineralization, the reverse cation exchange process constitute an important mechanism controlling groundwater mineralization with enhancing risk of saltwater intrusion. Environmental isotope tracers reveal that groundwater is evolving within an op...
Abstract Deep groundwater samples from the Continental Intercalaire (CI) aquifer in the Northern ... more Abstract Deep groundwater samples from the Continental Intercalaire (CI) aquifer in the Northern Tunisian Sahara have been analyzed for noble gases 3He, 4He, Ne and 81Kr, and for 14C to better constrain the groundwater residence time of this large transboundary aquifer. Its significant radiogenic 4He content and background-level 14C both indicate water older than a few tens of thousands of years. Distinct helium concentrations and Ne/He ratios suggest different groundwater flow paths through the Tozeur and Kebili regions. 81Kr is applied for the first time on the CI aquifer, providing more direct evidence for the presence of old groundwater with 81Kr/Kr ratios at 63% – 15% of the atmospheric value, corresponding to residence times of 150 – 630 ka. These newly obtained 81Kr ages enable a re-evaluation of the previously reported data from the Tozeur region in order to better constrain the input values of 36Cl/Cl and Cl. The initial 36Cl/Cl ratio is found to be 4 – 6 times larger than previously assumed, and the initial Cl concentration 6 – 15 times smaller. The results of 81Kr dating and the recalibrated 36Cl dating define an eastward age progression across >500 km of flow path from the Algerian to Tunisian sections. This study exemplifies the utility of 81Kr not only as an independent and conservative chronometer, but also as a supplemental measurement to better calibrate the parameters required for other age tracers, including cosmogenic 36Cl and radiogenic 4He.
A research has been carried out to investigate the effects of below sea level mining on the cemen... more A research has been carried out to investigate the effects of below sea level mining on the cement raw material quality of a limestone quarry located adjacent to the shoreline near Darica-Kocaeli-Turkey. Field studies involved rock mass characterization through discontinuity surveys performed at the working benches of the quarry as well as on the core samples, monitoring of groundwater levels, performance of water pressure tests, and in-situ hydrochemical measurements. Hydrogeological data suggest that the carbonate sequence forms a poor unconfined aquifer having hydraulic conductivity values ranging between 10 À6 m/s and 10 À8 m/s. In the quarry, water seepages can only be observed at the shear zones. Electrical conductivity profiles taken from the boreholes located at various distances from the shore line indicated the present position of the salt water wedge.
HAL (Le Centre pour la Communication Scientifique Directe), 2013
Niger is the largest nation in West Africa (with 1.26 million km2), located between the Sahara an... more Niger is the largest nation in West Africa (with 1.26 million km2), located between the Sahara and sub- Saharan regions without coast line. The majority of the country is covered by desert. Low precipitation (151 mm per year in 2009, World Bank 2010) and recurring droughts have made groundwater an essential water source. In the Diffa region (ca. 150 000 km2), located in south-eastern Niger and in the north-west of Lake Chad, groundwater is an important water source for the local population, together with surface water from Lake Chad and less importantly from the Komadougou Yobe River. A decreasing trend in rainfall, and hence shrinking of the area around Lake Chad, and irrigation development proposed by Nigerian authorities to meet growing food demand have led to actual and potential increases in groundwater exploitation. Moreover, water from Lake Chad has high salt content, limiting its usage. Groundwater resources in the region are found in several aquifer systems: (a) the Manga Quaternary aquifer covering nearly the entire Diffa region at 20 m to more than 50 m depth, except in a central part of the region (less than 10 m depth); (b) the alluvial aquifer located in the Komadougou valley and in topographic depressions of the region at a shallow depth (less than 10 m); (c) the Pliocene aquifer in the Pliocene sands and silts, covering the entire region at about 300 m depth in most of the region or at about 200 m in the central part; (d) the Continental Intercalary/Hamadien aquifer, covering the entire region at 40 to 60 m depth with a very low or zero recharge rate. To improve groundwater resource use and management of the potable water supply in the Diffa region, Technical Cooperation project NER8011 was conducted from 2009- 2012 to characterize the Manga Quaternary aquifer system. The project was entitled Studying the Recharge Process and the Status of Mineral Deposits Within the Manga Aquifer (Diffa region). The project was implemented by le Ministere de L'Hydraulique et de l'Environnement, Direction des Ressources en Eau of Niger
The assessment of nitrate pollution origin using stable isotope techniques is a fundamental prere... more The assessment of nitrate pollution origin using stable isotope techniques is a fundamental prerequisite for the application of sustainable groundwater management plans. Although nitrate pollution is a worldwide groundwater quality problem, existing knowledge on the origin of nitrate pollution in arid and semi-arid regions is still scarce. Using the example of the Grombalia aquifer (NE Tunisia), this work summarizes the main strengths and constraints of multi-isotope techniques targeting at nitrate source identification and apportionment The results highlighted that, even in the case of well-established methodologies, like those of isotope hydrogeochemistry (δ15NNO3, δ 18ONO3 and δ 11B) and mixing modelling for source apportionment, it is fundamental to take into account regional and local end-members to avoid biased data interpretation and to fully exploit the potential of such accurate tools.
Nitrate contamination still remains one of the main groundwater quality issues in several aquifer... more Nitrate contamination still remains one of the main groundwater quality issues in several aquifers worldwide, despite the perduring efforts of the international scientific community to effectively tackle this problem. The classical hydrogeological and isotopic investigations are obviously of paramount importance for the characterization of contaminant sources, but are clearly not sufficient for the correct and long-term protection of groundwater resources. This paper aims at demonstrating the effectiveness of the socio-hydrogeological approach as the best tool to tackle groundwater quality issues, while contributing bridging the gap between science and society. An integrated survey, including land use, hydrochemical (physicochemical parameters and major ions) and isotopic (d 15 NNO3 and d 18 ONO3) analyses, coupled to capacity building and participatory activities was carried out to correctly attribute the nitrate origin in groundwater from the Grombalia Basin (North Tunisia), a region where only synthetic fertilizers have been generally identified as the main source of such pollution. Results demonstrates that the basin is characterized by high nitrate concentrations, often exceeding the statutory limits for drinking water, in both the shallow and deep aquifers, whereas sources are associated to both agricultural and urban activities. The public participation of local actors proved to be a fundamental element for the development of the hydrogeological investigation, as it permitted to obtain relevant information to support data interpretation, and eventually guaranteed the correct assessment of contaminant sources in the studied area. In addition, such activity, if adequately transferred to regulators, will ensure the effective adoption of management practices based on the research outcomes and tailored on the real needs of the local population, proving the added value to include it in any integrated investigation.
... by northeast-southwest fold belts bordered by fault corridor systems and separated by basins ... more ... by northeast-southwest fold belts bordered by fault corridor systems and separated by basins filled with Mio???Plio???Quaternary deposits (Burollet 1956; Khessibi 1978; Ben Ayed 1986; Boukadi 1994; B??dir 1995; Chekhma 1996; Ben youssef 1999 ... Hamdi Neji ... Md B Hassen W.20 ...
Patterns and Mechanisms of Climate, Paleoclimate and Paleoenvironmental Changes from Low-Latitude Regions, 2019
In the present context of climate change and increasing demand for water, it is crucial to identi... more In the present context of climate change and increasing demand for water, it is crucial to identify the origin, groundwater flow dynamics and mean residence times for sustainable management of water resources. In this study, groundwater residence time and recharge conditions of the deep aquifer of Sfax were investigated using environmental isotopes and noble gases. The results show that Sfax deep groundwater was recharged during cooler period of Late Pleistocene. In broad agreement with evidence from other paleoclimate investigations, the estimated noble gas recharge temperature (NGT) is lower than the present by about 5.5 °C. Oxygen isotopes values of Late Pleistocene are also 1.5‰ lower than modern precipitation.
Abstract The Complex Terminal Aquifer in Kebili basin (CTAK) is one of the most important deep gr... more Abstract The Complex Terminal Aquifer in Kebili basin (CTAK) is one of the most important deep groundwater reserves in the North West Aquifer Sahara System (NWASS). It plays a crucial role in the regional socio-economic development as it represents the main source of water supply in the region. However, the exploitation increases given rise to a grave water quality degradation and a gradual hydraulic head lowering. Using geostatistical and modelling methods and geochemical tools, this investigation aims to: (i) improve the understanding of hydrogeological structure of the aquifer through more precise maps; (ii) evaluate the quality of the CTAK groundwater and their compliance with international standards; (iii) develop an integrated hydrogeological conceptual model able to describe the hydrodynamic functioning of the aquifer. The calculated recharge and flow rates, using carbon 14 activities, are very low confirming the long residence time of CTAK groundwater. The use of quality indicators proves that 51% of the groundwater samples show poor quality for drinking purposes. In terms of agricultural activities, only 6% of waters are good to permissible for irrigation purposes, while 44% are doubtful for use. Based on this multidisciplinary analysis, the established hydrogeological conceptual model will provide a required basis for futures numerical groundwater flow models used in the management strategies under these conditions.
Major element concentrations and stable (δ18O and δ2H) and radiogenic (3H and 14C) isotopes in gr... more Major element concentrations and stable (δ18O and δ2H) and radiogenic (3H and 14C) isotopes in groundwater have proved useful tracers for understanding the geochemical processes that control groundwater mineralization and for identifying recharge sources in the semi-arid region of Sfax (southeastern Tunisia). Major-ion chemical data indicate that the origins of the salinity in the groundwater are the water–rock interactions, mainly the dissolution of evaporitic minerals, as well as the cation exchange with clay minerals. The δ18O and δ2H relationships suggest variations in groundwater recharge mechanisms. Strong evaporation during recharge with limited rapid water infiltration is evident in the groundwater of the intermediate aquifer. The mixing with old groundwater in some areas explains the low stable isotope values of some groundwater samples. Groundwaters from the intermediate aquifer are classified into two main water types: Ca-Na-SO4 and Ca-Na-Cl-SO4. The high nitrate concentr...
In a semi-arid to arid climate region, socio-economic development is mainly dependent on deep gro... more In a semi-arid to arid climate region, socio-economic development is mainly dependent on deep groundwater resources. This is the case of the Continental Intercalaire (CI) groundwater which is one of the most important aquifers in the North Western Sahara in Africa. This aquifer system, extending over more than a million of km2, is mainly confined, poorly recharged but intensely abstracted in Southern Tunisia. Efficient management of this resource relies on accurate data such as recharge/discharge rate and groundwater dynamics. In this study, environmental isotopes (2H, 18O, 13C, and 14C) were combined with long time lived radio-nuclide (81Kr) to give greater constraint on the groundwater residence time in the CI. Stable isotope signature is depleted compared to the modern rainwater of Sfax station with very low deuterium excess suggesting a paleoclimatic effect. This finding is strongly supported by 14C measurements where most of the analyzed samples are below the detection limit. T...
Groundwater is the major source of water supply in many rural and urban areas located within the ... more Groundwater is the major source of water supply in many rural and urban areas located within the Volta river basin in Benin [1] (Fig.1). This river basin is located in the Sudano-Sahelian zone, which is characterized by a contrasting geomorphology of hill chains extending from the East to the Center, and a lowland in its western part. The mean annual rainfall and potential evapotranspiration is 1173 mm and 1494 mm, respectively [2]. In the West, the sedimentary sequences are monoclinic and comprise the sedimentary basin of Pendjari. They become gradually folded towards the East [3]. Four geological sub-units can be distinguished within the studied area, namely (from West to East): the Pendjari sedimentary basin, Buem, Atacora and the basement s.s. formation. The northern area is occupied by the Pendjari National Park surrounded by rural areas where intensive population growth occurs . A better assessment of groundwater resources in this area is a strategic point for the sustainable ...
Groundwater resources are facing increasing pressure especially in semi-arid regions where they o... more Groundwater resources are facing increasing pressure especially in semi-arid regions where they often represent the main freshwater resource to sustain human needs. Several aquifers in the Mediterranean basin suffer from salinization and quality degradation. This study provides an assessment of Grombalia coastal aquifer (Tunisia) based on multidisciplinary approach that combines chemical and isotopic (δ2H, δ18O, 3H, 14C and δ13C) methods to characterize the relation between groundwater quality variation and aquifer recharge. The results indicate that total dissolved solids exceed 1000 mg/L in the most of samples excepting the recharge area. In addition to water–rock interaction, evaporation and nitrate pollution contributing to groundwater mineralization, the reverse cation exchange process constitute an important mechanism controlling groundwater mineralization with enhancing risk of saltwater intrusion. Environmental isotope tracers reveal that groundwater is evolving within an op...
Abstract Deep groundwater samples from the Continental Intercalaire (CI) aquifer in the Northern ... more Abstract Deep groundwater samples from the Continental Intercalaire (CI) aquifer in the Northern Tunisian Sahara have been analyzed for noble gases 3He, 4He, Ne and 81Kr, and for 14C to better constrain the groundwater residence time of this large transboundary aquifer. Its significant radiogenic 4He content and background-level 14C both indicate water older than a few tens of thousands of years. Distinct helium concentrations and Ne/He ratios suggest different groundwater flow paths through the Tozeur and Kebili regions. 81Kr is applied for the first time on the CI aquifer, providing more direct evidence for the presence of old groundwater with 81Kr/Kr ratios at 63% – 15% of the atmospheric value, corresponding to residence times of 150 – 630 ka. These newly obtained 81Kr ages enable a re-evaluation of the previously reported data from the Tozeur region in order to better constrain the input values of 36Cl/Cl and Cl. The initial 36Cl/Cl ratio is found to be 4 – 6 times larger than previously assumed, and the initial Cl concentration 6 – 15 times smaller. The results of 81Kr dating and the recalibrated 36Cl dating define an eastward age progression across >500 km of flow path from the Algerian to Tunisian sections. This study exemplifies the utility of 81Kr not only as an independent and conservative chronometer, but also as a supplemental measurement to better calibrate the parameters required for other age tracers, including cosmogenic 36Cl and radiogenic 4He.
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