排序方式： 共有13条查询结果，搜索用时 15 毫秒
1.
Thirty-two groundwater samples collected from the Merguellil Wadi basin (central Tunisia) complemented by the Haouareb dam reservoir water samples have been isotopically analysed in order to investigate the implication of the reservoir water to recharging the aquifer, and also to infer the sources, relative ages and mixing processes in the aquifer system. Plots of the stable isotopes data against the local meteoric lines of Tunis-Carthage and Sfax indicate a strong implication of the dam water noticeable up to a distance of 6–7 km. A contribution as much as 80% of the pumped water has been evidenced using isotopic mass balance. In addition, poorly distinguished water clusters in the stable isotope plots, but clearly identified in the diagrams δ18O versus 3H and 3H versus 14C, indicate various water types related to sources and timing of recharge. The isotopic signatures of the dam accounting water, the “old” and “native” recharged waters, have been evidenced in relation to their geographical distribution and also to their radiogenic isotopes (3H and 14C) contents. In the south-western part of the aquifer, mixing process occurs between the dam reservoir water and both the “old” and “native” water components. 相似文献
2.
Geochemical and isotopic investigation of the aquifer system in the Djerid-Nefzaoua basin, southern Tunisia 总被引：2，自引：0，他引：2
In the Djerid-Nefzaoua region, southern Tunisia, about 80% of agricultural and domestic water supply is provided by the complex terminal (CT) aquifer. However, 20% of this demand is provided by other hydraulically connected aquifers, namely the continental intercalaire (CI) and the Plio-Quaternary (PQ). Overexploitation of the CT aquifer for agricultural practices has contributed to the loss of the artesian condition and the decline of groundwater level which largely increased the downward leakage from the shallow PQ aquifer. Excess irrigation water concentrates at different rates in the irrigation channels and in the PQ aquifer itself. Then, it returns to the CT aquifer and mixes with water from the regional flow system, which contributes to the salinization of the CT groundwater. A geochemical and isotopic study had been undertaken over a 2-years period in order to investigate the origin of waters pumped from the CT aquifer with an emphasis on its hydraulic relationships with the underlying and the overlying CI and PQ aquifers. Geochemistry indicates that groundwater samples collected from different wells show an evolution of the water types from Na-Cl to Ca-SO4-Cl. Dissolution of halite, gypsum and anhydrite-bearing rocks is the main mechanism that leads to the salinization of the groundwater. Isotopic data indicate the old origin of all groundwater in the aquifer system. Mixing and evaporation effects characterizing the CT and the PQ aquifers were identified using δ2H and δ18O relationship and confirmed by the conjunction of δ2H with chloride concentration. 相似文献
3.
4.
Groundwater origins and mixing pattern in the multilayer aquifer system of the Gafsa-south mining district: a chemical and isotopic approach 总被引：3，自引：2，他引：1
Younes Hamed Lassaad Dassi Meriem Tarki Riadh Ahmadi Khalid Mehdi Hamed Ben Dhia 《Environmental Earth Sciences》2011,63(6):1355-1368
Major ion geochemistry and environmental isotopes were used to identify the origins and the mineralisation processes of groundwater
flowing within the three aquifer levels of the multilayer system of the Gafsa-south mining district (Southwestern Tunisia).
It has been demonstrated that groundwaters are characterised by a Ca–Mg–SO4 water type. Geochemical pattern is mainly controlled by the dissolution of halite, gypsum and/or anhydrite as well as by
the incongruent dissolution of dolomite. δ18O and δ2H values are much lower than the isotopic signature of regional precipitation and fall close to the meteoric water lines,
indicating that groundwaters have not been significantly affected by evaporation or mineral–water reactions. The distribution
of stable and radiogenic isotopes (δ18O, δ2H, δ13C and 14C) within the aquifer levels suggests that the deep confined aquifer receives a significant modern recharge at higher altitudes,
while, the shallow unconfined aquifer has been mainly recharged under cooler paleoclimatic condition, likely during Late Pleistocene
and Early Holocene humid periods. However, waters from the intermediate confined/unconfined aquifer have composite isotopic
signatures, highlighting that they are derived from a mixture of the two first end-members. 相似文献
5.
Investigation by multivariate analysis of groundwater composition in a multilayer aquifer system from North Africa: A multi-tracer approach 总被引：1，自引：0，他引：1
Lassaad Dassi 《Applied Geochemistry》2011,26(8):1386-1398
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. δ18O vs. δ2H and δ18O vs. 14C 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 3H concentrations, low 14C 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 3H concentrations, high 14C 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. 相似文献
6.
Hanen Azaza Lassaad Mechi Amira Doggaz Virgil Optasanu Mohamed Tlili Mohamed Ben Amor 《Arabian Journal of Geosciences》2017,10(10):220
During the production of hydrocarbons from subterranean reservoirs, scaling with calcium carbonate and barium sulfate causes flux decline and dangerous problems in production facilities. This work is intended to study the effect of calcium ions on the precipitation of barium sulfate (barite); then, the effect of the formed barite on calcium carbonate crystallization. The conductometric and pH methods were used to follow the progress of the precipitation reaction in aqueous medium. The obtained precipitates were characterized by FTIR, RAMAN, SEM, and XRD. It was shown that Ca2+ in the reaction media does not affect the microstructure of barite even for higher calcium–barium molar ratio. It influences the precipitation kinetics and the solubility of barite by the formation of CaSO4° ion pairing as a predominant role of complex formation (CaSO4) and the increase of the ionic strength. In Ca(HCO3)2-BaSO4-NaCl aqueous system, experiments have showed that added or formed barite in the reaction media accelerates calcite precipitation. No effect on the microstructure of heterogeneous formed calcite which remain calcite shape. However the presence of carbonate ions affects slightly the microstructure of barite. 相似文献
7.
Geotectonics - Tunisia had been the place of various tectonic episodes which have drawn the actual structural map of the country. The Neogene period was the most active period in which the... 相似文献
8.
Meriem Tarki Lassaad Dassi Younes Hamed Younes Jedoui 《Environmental Earth Sciences》2011,64(1):85-95
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-pumping
and the large-scale flood irrigation practices, (2) determine the principal mineralization processes of its fossil groundwater,
and (3) examine the mode of recharge of this aquifer and whether it contains part of modern hydrological regime. The observed
geochemical patterns indicated that the main mineralization processes affecting the CT groundwater water/rock interactions
and mixing. The native Na > Cl and Cl > SO4 > Ca > Na waters, resulting from the dissolution of halite and gypsum and from pyrite oxidation, interacted with those of
the underlying and the overlying aquifers without changing their chemical facies. Stable isotope data provided evidences about
upward and downward leakage into the CT aquifer and their relationships with anthropogenic activities. They demonstrated that
the long-term over-pumping of the CT aquifer, which contributed to the loss of its potentiometric pressure, favored the upward
leakage of the artesian deep groundwater along parts of the major faults. Moreover, the large-scale flood irrigation practices
in the oases domain, which ensured the recharge of the shallow water table by return flow, enhanced the downward leakage toward
the CT aquifer. 相似文献
9.
International Journal of Earth Sciences - New field observations carried out in northeastern Tunisia (Kechabta Neogene basin) allowed us to clarify and pinpoint the chronology of the folding phases... 相似文献
10.
Lassaad Dassi 《Environmental Earth Sciences》2010,60(4):861-871
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 post-nuclear 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%. 相似文献