Please use this identifier to cite or link to this item: https://dspace.univ-ouargla.dz/jspui/handle/123456789/16366
Title: Contribution à l’étude des indices de dégradation et de quelques Éléments traces dans les écosystèmes lacustres chotts et sebkhas du Bas Sahara Algérien
Authors: Messaoud ,HACINI
BELLAOUEUR, Abdelaziz
Keywords: Saumure
Modèle thermodynamique
Eléments Traces
ndice de dégradation
Ecosystème lacustre
Chott
Sebkha
Bas Sahara
Brine
Trace Elements
Degradation index
lacustrine ecosystem
Chott
Sebkha
Brine
Thermodynamic model
Degradation
index
lacustrine ecosystem
Chott
Sebkha
Lower Sahara
Trace Elements
Issue Date: 2017
Abstract: Les saumures, dans les écosystèmes lacustres chotts et sebkhas du Bas Sahara Algérien, sont des solutions fortement concentrés en sels minéraux avec une salinité qui dépasse largement celle des eaux des mers (120 à 440g/l). Pour déterminer l’état de saturation de ces saumures vis-à-vis de principales espèces chimiques, on utilise le modèle thermodynamique PHREEQC v3. La première interprétation des données, permet de spécifier le faciès chimique principalement chloruré sodique. En effet, on utilise ce modèle thermodynamique pour calculer l’équilibre minéraux/solution sous différentes hypothèses. Le test de ces différentes hypothèses montre que chacune a ses limites dans la simulation des comportements thermodynamiques des saumures. L’analyse chimique a permis de mettre en relief le degré élevé de pollution de ces saumures par certains Eléments Traces (ET), notamment Sr, Cu, Zn et Ti. Les teneurs moyennes sont respectivement de l’ordre de 22,5 ; 2,9 ; 2,3 et 0,6 mg/l. Pour les sels solides, les teneurs moyennes sont de l’ordre de 31mg/l (de Sr), 1,8mg/l (de Cu) et 0,6mg/l (de Ti). Ces résultats sont approfondis par l’analyse d’images ponctuelles au MEB. Ce sont essentiellement les silicates, les sulfates et les oxydes qui constituent l’origine de ces ET, avec prédominance des minéraux évaporitiques et argileux. La pratique encore répandue du "tout à l'égout", maitre en évidence l’impact environnemental des rejets d’eaux usées sur ces écosystèmes lacustres. 0,01 à 6768mg/l charge en matière minérale exprimée en terme de nitrates a été enregistrée. En termes de phosphate, elle est de l’ordre de 0,2 à 9mg/l. La charge en matière organique exprimée en termes de DCO, DBO5 et MES, elle est respectivement de 82 à 340mg/l, de 28 à 123mg/l, et de 67 à 149mg/l. L’examen de ces résultats et les rapports (DCO/DBO5 >3) soulignent très bien les indices de dégradation des saumures et le caractère insatisfaisant de biodégradabilité des rejets d’eaux usées dans ces écosystèmes lacustres.Abstract The Brines of chotts in Algerian Lower Sahara are highly concentrated solutions of mineral salts with a salinity that far exceeds that of the sea water (120 to 440g/l). Databases of the thermodynamic model PHREEQC v3 were used to determine the saturated state of the brines with respect to principal chemical species. The first interpretation of data allows to specify the chemical facies of these brines form their chemical compositions. They have mainly a very marked sodic chlorinated character. Indeed, we use the thermodynamic model PHREEQC v3 to calculate the mineral/solutions equilibria on the basis of different assumptions. The test of these assumptions shows that each one has its limits to simulate and control the thermodynamic behavior of the brines. Chemical analysis shows the high degree of pollution of these brines by certain Trace Elements (TE), in particular Sr, Cu, Zn and Ti. The mean contents are respectively of 22.5; 2.9; 2.3 and 0.6mg/l. For solid salts, the average contents are 31mg/l (of Sr), 1.8mg/l (of Cu) and 0.6mg/l (of Ti). These results are investigated by the analysis of point images at the (MEB). It is essentially silicates, sulphate and oxides that are the origin of these (TEs), with predominantly evaporite and clay minerals. The still widespread practice of “sewerage” highlights the environmental impact of wastewater discharges on these lake ecosystems. 0.01 to 6768mg/l load of mineral matter expressed in terms of nitrates was recorded. In terms of phosphate, it is of the order of 0.2 to 9mg/l. The organic matter load expressed in terms of COD, BOD5 and (SM) is 82 to 340mg/l, 28 to 123mg/l, and 67 to 149mg/l, respectively. The examination of these results and the reports (COD/BOD5 > 3) show very well the indices of degradation of brine and the unsatisfactory biodegradability of wastewater discharges in these lacustrine ecosystems.
The Brines of chotts in Algerian Lower Sahara are highly concentrated solutions of mineral salts with a salinity that far exceeds that of the sea water (120 to 440g/l). Databases of the thermodynamic model PHREEQC v3 were used to determine the saturated state of the brines with respect to principal chemical species. The first interpretation of data allows to specify the chemical facies of these brines form their chemical compositions. They have mainly a very marked sodic chlorinated character. Indeed, we use the thermodynamic model PHREEQC v3 to calculate the mineral/solutions equilibria on the basis of different assumptions. The test of these assumptions shows that each one has its limits to simulate and control the thermodynamic behavior of the brines. Chemical analysis shows the high degree of pollution of these brines by certain Trace Elements (TE), in particular Sr, Cu, Zn and Ti. The mean contents are respectively of 22.5; 2.9; 2.3 and 0.6mg/l. For solid salts, the average contents are 31mg/l (of Sr), 1.8mg/l (of Cu) and 0.6mg/l (of Ti). These results are investigated by the analysis of point images at the (MEB). It is essentially silicates, sulphate and oxides that are the origin of these (TEs), with predominantly evaporite and clay minerals. The still widespread practice of “sewerage” highlights the environmental impact of wastewater discharges on these lake ecosystems. 0.01 to 6768mg/l load of mineral matter expressed in terms of nitrates was recorded. In terms of phosphate, it is of the order of 0.2 to 9mg/l. The organic matter load expressed in terms of COD, BOD5 and (SM) is 82 to 340mg/l, 28 to 123mg/l, and 67 to 149mg/l, respectively. The examination of these results and the reports (COD/BOD5 > 3) show very well the indices of degradation of brine and the unsatisfactory biodegradability of wastewater discharges in these lacustrine ecosystems.
Description: Géologie
URI: http://dspace.univ-ouargla.dz/jspui/handle/123456789/16366
Appears in Collections:Département des Sciences de la terre et de l’Univers - Doctorat

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