Lassaad Dassi | University of Tunisia (original) (raw)
Papers by Lassaad Dassi
Journal of African Earth Sciences, 2016
Hydrological Sciences Journal, 2012
Mineralogical Magazine, 2008
In many areas of south and south-eastern Asia, concentrations of As in ground water have been fou... more In many areas of south and south-eastern Asia, concentrations of As in ground water have been found to exceed the WHO maximum concentration limit of 10 mg/l. This is adversely affecting the health of millions of people and has grave current and future health implications. It has recently been suggested that extensive abstraction of ground water in these areas may accelerate the release of As to ground water. This study uses geochemical and isotopic data to assess this hypothesis. The area investigated in this study is in the Chakdaha block of the Nadia District, West Bengal. The ground water is predominantly of the Ca-Mg-HCO 3 type, although some samples were found to contain elevated concentrations of Na, Cl and SO 4 . This is thought to reflect a greater degree of water-rock interaction at the locations of these particular samples. Arsenic concentrations exceeded the national limit of 50 mg/l in 13 of the 22 samples collected. Four of the 13 samples with high As were recovered from tubewells with depths of 60 m or more. Shallow ground water samples were found to have a stable isotopic composition which falls subparallel to the Global Meteoric Water Line. This probably represents a contribution of evaporated surface water to the ground water, possibly from surface ponds or re-infiltrating irrigation water. Deep ground water, conversely, was shown to have a composition that closely reflects that of meteoric water. The data presented in this study suggest that, whilst the drawdown of surface waters may drive As release in shallow ground waters, it is not responsible for driving As release in deep ground water. However, local abstraction may have resulted in changes in the ground water flow regime of the area, with contaminated shallow ground waters being drawn into previously uncontaminated deep aquifers.
New and previously published data sets including stable and radiogenic isotope measurements (18O,... more New and previously published data sets including stable and radiogenic isotope measurements (18O, 2H, 3H,13C and 14C) were used to investigate, conceptualize and compare groundwater hydrodynamics within three major multilayer aquifer systems located in central and southern Tunisia. It has been demonstrated that the investigated
aquifer systems contain modern and palaeoclimatic waters. Modern groundwaters, which refer to contemporaneous and post-nuclear recharge waters, are characterized by enriched stable isotope contents, high carbon-14 activities and high to moderate tritium concentration. While, palaeoclimatic groundwaters, which refer to Late Pleistocene and Early Holocene recharge waters, are distinguished by their depleted stable isotope contents, low carbon-14 activities and insignificant tritium concentrations. Established conceptual models have elucidated the groundwater hydrodynamics within the studied aquifer systems. They show that groundwater mixing occurs between end-members from the shallow and deep aquifers that migrate by downward and upward leakage towards the intermediate aquifer
Applied geochemistry, Jan 1, 2011
Editorial handling by A. Danielsson a b s t r a c t A multi-tracer approach has been carried out ... more Editorial handling by A. Danielsson a b s t r a c t A multi-tracer approach has been carried out in the Sbeïtla multilayer aquifer system, central Tunisia, to investigate the geochemical evolution, the origin of groundwaters and their circulation patterns. It involves statistical data analysis coupled with the definition of the hydrochemical and isotopic features of the different groundwaters. Principal Components Analysis (PCA) of geochemical data used in conjunction with bivariate diagrams of major and trace elements indicate that groundwater mineralization is mainly controlled by water-rock interaction and anthropogenic processes in relation to return flow of irrigation waters. The PCA of isotopic data and bivariate conventional diagrams of stable and radiogenic isotopes i.e. d 18 O vs. d 2 H and d 18 O vs. 14 C provide valuable information about the origin and the circulation patterns of the different groundwater groups. They permit classifying groundwaters into three groups. The first group is characterized by low 3 H concentrations, low 14 C activities and depleted stable isotope contents. It corresponds to an old end-member in relation with palaeoclimatic recharge which occurred during the Late Pleistocene and the Early Holocene humid periods. The second group is distinguished by high to moderate 3 H concentrations, high 14 C activities and enriched heavy isotope signatures. It corresponds to a modern end-member originating from a mixture of post-nuclear and present-day recharge in relation to return flow of irrigation waters. The third group is characterized by an average composition of stable and radiogenic isotope signatures. It provides evidence for the mixing between the upward moving palaeoclimatic end-member and the downward moving present-day end-member.
Environmental Earth Sciences, Jan 1, 2011
Abstract The Complex Terminal (CT) confined aquifer of the Djerid basin, southwestern Tunisia, wa... more Abstract The Complex Terminal (CT) confined aquifer of the Djerid basin, southwestern Tunisia, was studied using major ion concentrations and stable isotope contents in order to (1) investigate the changes on its hydrodynamic functioning due to the long-term over-...
Environmental Earth …, Jan 1, 2010
Hydrological sciences journal, Jan 1, 2006
Approche hydrogéologique et hydrochimique des échanges hydrodynamiques entre aquifères profond et... more Approche hydrogéologique et hydrochimique des échanges hydrodynamiques entre aquifères profond et superficiel du bassin du.
Environmental Geology, Jan 1, 2005
Environmental Earth Sciences, Jan 1, 2010
The scarcity of surface water resources in arid and semi-arid regions from North African countrie... more The scarcity of surface water resources in arid and semi-arid regions from North African countries contributes to the considerable increase of groundwater exploitation, which leads to the development of hydrogeological studies. However, due to the lack of hydrodynamic data in these regions, these studies focus more and more on the geochemical and environmental isotope techniques to insure a better understanding of the hydrodynamic functioning of subsurface systems. In this study, which interests an important unconfined aquifer in central Tunisia, tritium data and chloride mass balance (CMB) method were applied in order to (1) understand the mode of recharge of this aquifer and (2) obtain a reliable estimation of its recharge amount as well as (3) estimate its annual renewal rate. It has been demonstrated that the shallow groundwaters are classified into two groups according to their tritium contents. The first group includes wells located mainly downstream and highlights the significant role of the postnuclear lineal recharge through Wadis courses. The second group encloses wells located practically overall the rest of the basin and refers to relatively modern waters originated from areal recharge of present-day rainfall. Based on the CMB method, the recharge to this unconfined aquifer is estimated to 31.7 mm year -1 , which corresponds to 10.5% of the total rainfall. The annual renewal rate of groundwater, evaluated based on the tritium contents, is up to 16%.
Hydrological Sciences …, Jan 1, 2008
Major ion geochemistry, and water molecule isotopes ( 18 O, 2 H) and radiogenic carbon ( 14 C) of... more Major ion geochemistry, and water molecule isotopes ( 18 O, 2 H) and radiogenic carbon ( 14 C) of dissolved inorganic carbon (DIC) were used to investigate the hydrodynamic functioning of the multilayer aquifer system in the Moulares-Redayef basin, southern Tunisia. The groundwater of different aquifer levels is characterized by sulphate to calcium sulphate water type. The major geochemical processes in the aquifer system are evaporite mineral dissolution and mixing. The isotopic study allows two groundwater types to be identified: an old palaeoclimatic groundwater, marked by low 14 C activity and relatively depleted stable isotope ( 18 O and 2 H) content characterizes the shallowest aquifers of the Plio-Quaternary and Miocene formations; however, a recent groundwater, distinguished by relatively high 14 C activity and slightly enriched 18 O and 2 H content, characterizes the deep Upper Cretaceous artesian aquifer. In addition to these two water groups, other groundwaters are identified, indicating a mixing effect. Etude géochimique et isotopique du système aquifère multicouche du bassin de Moulares-Redayef, sud tunisien Resume Une étude géochimique et isotopique, basée sur l'utilisation des éléments majeurs et des isotopes de la molécule d'eau ( 18 O, 2 H) et du CITD (Carbone Inorganique Total Dissous) ( 14 C), a été entreprise pour étudier le fonctionnement hydrodynamique du système aquifère multicouche du bassin de Moulares-Redayef, situé au sud de la Tunisie. Les eaux souterraines des différents niveaux aquifères sont caractérisées par un faciès sulfaté à sulfaté calcique. Les processus géochimiques majeurs du système aquifère sont la dissolution et le mélange des minéraux évaporitiques. L'étude isotopique permet d'identifier deux groupes d'eaux souterraines. D'une part, les eaux anciennes paléoclimatiques, à faibles activités 14 C et à teneurs isotopiques (en 18 O et 2 H) appauvries, caractérisent les aquifères superficiels des formations plio-quaternaire et miocène. D'autre part, les eaux récentes, à fortes activités 14 C et à teneurs relativement enrichies en 18 O et en 2 H, caractérisent l'aquifère profond à nappe artésienne du Crétacé supérieur. En plus de ces deux groupes, d'autres eaux souterraines sont identifiées, qui indiquent un phénomène de mélange.
Environmental Geology, Jan 1, 2005
Environmental Geology, Jan 1, 2005
CITATIONS 47 READS 120 4 authors, including:
Journal of African Earth Sciences, 2016
Hydrological Sciences Journal, 2012
Mineralogical Magazine, 2008
In many areas of south and south-eastern Asia, concentrations of As in ground water have been fou... more In many areas of south and south-eastern Asia, concentrations of As in ground water have been found to exceed the WHO maximum concentration limit of 10 mg/l. This is adversely affecting the health of millions of people and has grave current and future health implications. It has recently been suggested that extensive abstraction of ground water in these areas may accelerate the release of As to ground water. This study uses geochemical and isotopic data to assess this hypothesis. The area investigated in this study is in the Chakdaha block of the Nadia District, West Bengal. The ground water is predominantly of the Ca-Mg-HCO 3 type, although some samples were found to contain elevated concentrations of Na, Cl and SO 4 . This is thought to reflect a greater degree of water-rock interaction at the locations of these particular samples. Arsenic concentrations exceeded the national limit of 50 mg/l in 13 of the 22 samples collected. Four of the 13 samples with high As were recovered from tubewells with depths of 60 m or more. Shallow ground water samples were found to have a stable isotopic composition which falls subparallel to the Global Meteoric Water Line. This probably represents a contribution of evaporated surface water to the ground water, possibly from surface ponds or re-infiltrating irrigation water. Deep ground water, conversely, was shown to have a composition that closely reflects that of meteoric water. The data presented in this study suggest that, whilst the drawdown of surface waters may drive As release in shallow ground waters, it is not responsible for driving As release in deep ground water. However, local abstraction may have resulted in changes in the ground water flow regime of the area, with contaminated shallow ground waters being drawn into previously uncontaminated deep aquifers.
New and previously published data sets including stable and radiogenic isotope measurements (18O,... more New and previously published data sets including stable and radiogenic isotope measurements (18O, 2H, 3H,13C and 14C) were used to investigate, conceptualize and compare groundwater hydrodynamics within three major multilayer aquifer systems located in central and southern Tunisia. It has been demonstrated that the investigated
aquifer systems contain modern and palaeoclimatic waters. Modern groundwaters, which refer to contemporaneous and post-nuclear recharge waters, are characterized by enriched stable isotope contents, high carbon-14 activities and high to moderate tritium concentration. While, palaeoclimatic groundwaters, which refer to Late Pleistocene and Early Holocene recharge waters, are distinguished by their depleted stable isotope contents, low carbon-14 activities and insignificant tritium concentrations. Established conceptual models have elucidated the groundwater hydrodynamics within the studied aquifer systems. They show that groundwater mixing occurs between end-members from the shallow and deep aquifers that migrate by downward and upward leakage towards the intermediate aquifer
Applied geochemistry, Jan 1, 2011
Editorial handling by A. Danielsson a b s t r a c t A multi-tracer approach has been carried out ... more Editorial handling by A. Danielsson a b s t r a c t A multi-tracer approach has been carried out in the Sbeïtla multilayer aquifer system, central Tunisia, to investigate the geochemical evolution, the origin of groundwaters and their circulation patterns. It involves statistical data analysis coupled with the definition of the hydrochemical and isotopic features of the different groundwaters. Principal Components Analysis (PCA) of geochemical data used in conjunction with bivariate diagrams of major and trace elements indicate that groundwater mineralization is mainly controlled by water-rock interaction and anthropogenic processes in relation to return flow of irrigation waters. The PCA of isotopic data and bivariate conventional diagrams of stable and radiogenic isotopes i.e. d 18 O vs. d 2 H and d 18 O vs. 14 C provide valuable information about the origin and the circulation patterns of the different groundwater groups. They permit classifying groundwaters into three groups. The first group is characterized by low 3 H concentrations, low 14 C activities and depleted stable isotope contents. It corresponds to an old end-member in relation with palaeoclimatic recharge which occurred during the Late Pleistocene and the Early Holocene humid periods. The second group is distinguished by high to moderate 3 H concentrations, high 14 C activities and enriched heavy isotope signatures. It corresponds to a modern end-member originating from a mixture of post-nuclear and present-day recharge in relation to return flow of irrigation waters. The third group is characterized by an average composition of stable and radiogenic isotope signatures. It provides evidence for the mixing between the upward moving palaeoclimatic end-member and the downward moving present-day end-member.
Environmental Earth Sciences, Jan 1, 2011
Abstract The Complex Terminal (CT) confined aquifer of the Djerid basin, southwestern Tunisia, wa... more Abstract The Complex Terminal (CT) confined aquifer of the Djerid basin, southwestern Tunisia, was studied using major ion concentrations and stable isotope contents in order to (1) investigate the changes on its hydrodynamic functioning due to the long-term over-...
Environmental Earth …, Jan 1, 2010
Hydrological sciences journal, Jan 1, 2006
Approche hydrogéologique et hydrochimique des échanges hydrodynamiques entre aquifères profond et... more Approche hydrogéologique et hydrochimique des échanges hydrodynamiques entre aquifères profond et superficiel du bassin du.
Environmental Geology, Jan 1, 2005
Environmental Earth Sciences, Jan 1, 2010
The scarcity of surface water resources in arid and semi-arid regions from North African countrie... more The scarcity of surface water resources in arid and semi-arid regions from North African countries contributes to the considerable increase of groundwater exploitation, which leads to the development of hydrogeological studies. However, due to the lack of hydrodynamic data in these regions, these studies focus more and more on the geochemical and environmental isotope techniques to insure a better understanding of the hydrodynamic functioning of subsurface systems. In this study, which interests an important unconfined aquifer in central Tunisia, tritium data and chloride mass balance (CMB) method were applied in order to (1) understand the mode of recharge of this aquifer and (2) obtain a reliable estimation of its recharge amount as well as (3) estimate its annual renewal rate. It has been demonstrated that the shallow groundwaters are classified into two groups according to their tritium contents. The first group includes wells located mainly downstream and highlights the significant role of the postnuclear lineal recharge through Wadis courses. The second group encloses wells located practically overall the rest of the basin and refers to relatively modern waters originated from areal recharge of present-day rainfall. Based on the CMB method, the recharge to this unconfined aquifer is estimated to 31.7 mm year -1 , which corresponds to 10.5% of the total rainfall. The annual renewal rate of groundwater, evaluated based on the tritium contents, is up to 16%.
Hydrological Sciences …, Jan 1, 2008
Major ion geochemistry, and water molecule isotopes ( 18 O, 2 H) and radiogenic carbon ( 14 C) of... more Major ion geochemistry, and water molecule isotopes ( 18 O, 2 H) and radiogenic carbon ( 14 C) of dissolved inorganic carbon (DIC) were used to investigate the hydrodynamic functioning of the multilayer aquifer system in the Moulares-Redayef basin, southern Tunisia. The groundwater of different aquifer levels is characterized by sulphate to calcium sulphate water type. The major geochemical processes in the aquifer system are evaporite mineral dissolution and mixing. The isotopic study allows two groundwater types to be identified: an old palaeoclimatic groundwater, marked by low 14 C activity and relatively depleted stable isotope ( 18 O and 2 H) content characterizes the shallowest aquifers of the Plio-Quaternary and Miocene formations; however, a recent groundwater, distinguished by relatively high 14 C activity and slightly enriched 18 O and 2 H content, characterizes the deep Upper Cretaceous artesian aquifer. In addition to these two water groups, other groundwaters are identified, indicating a mixing effect. Etude géochimique et isotopique du système aquifère multicouche du bassin de Moulares-Redayef, sud tunisien Resume Une étude géochimique et isotopique, basée sur l'utilisation des éléments majeurs et des isotopes de la molécule d'eau ( 18 O, 2 H) et du CITD (Carbone Inorganique Total Dissous) ( 14 C), a été entreprise pour étudier le fonctionnement hydrodynamique du système aquifère multicouche du bassin de Moulares-Redayef, situé au sud de la Tunisie. Les eaux souterraines des différents niveaux aquifères sont caractérisées par un faciès sulfaté à sulfaté calcique. Les processus géochimiques majeurs du système aquifère sont la dissolution et le mélange des minéraux évaporitiques. L'étude isotopique permet d'identifier deux groupes d'eaux souterraines. D'une part, les eaux anciennes paléoclimatiques, à faibles activités 14 C et à teneurs isotopiques (en 18 O et 2 H) appauvries, caractérisent les aquifères superficiels des formations plio-quaternaire et miocène. D'autre part, les eaux récentes, à fortes activités 14 C et à teneurs relativement enrichies en 18 O et en 2 H, caractérisent l'aquifère profond à nappe artésienne du Crétacé supérieur. En plus de ces deux groupes, d'autres eaux souterraines sont identifiées, qui indiquent un phénomène de mélange.
Environmental Geology, Jan 1, 2005
Environmental Geology, Jan 1, 2005
CITATIONS 47 READS 120 4 authors, including: