Growing populations and increasing industrialization causes increase in living standard, which result in decrease in the quality of water and may put stresses on natural waters by impairing both the quality of the water and the hydrological budget. This research aimed at determining the origin of the chemical elements of groundwater from the Oran Sebkha basin. It applied the inverse geochemical modeling to derive the sources of variation in the hydrochemistry. Fifty five (55) water samples were selected from different point in Oran Sebkha basin for sampling purpose in July 2011. Physico-chemical parameters such as pH and electric conductivity were measured in situ. Moreover, chloride, sulfate, alkalinity, calcium, magnesium, sodium, potassium, were measured in the laboratory. Inverse geochemical models of the statistical groups were developed using PHREEQC to elucidate the chemical reactions controlling water chemistry. The inverse geochemical modeling demonstrated that relatively few phases are required to derive water chemistry in the area. In a broad sense, the reactions responsible for the hydrochemical evolution in the area fall into three categories: (1) dissolution of evaporite minerals; (2) precipitation of carbonate minerals; and (3) weathering reactions of silicate minerals. The high values of the physico-chemical parameters of water obtained in the present study sites indicate a variation in the physico-chemical parameters and demonstrated that relatively few phases are required to derive water chemistry in the area. Range of values were found as pH (5.1-7.6), conductivity (720-15820 μS cm-1), chloride (994-7810 mg l-1), sulfate (6.1-112.4 mg l-1), alkalinity (421-19962 mg l-1), calcium (80-680 mg l-1), magnesium (212.4-4525 mg l-1), sodium (124.2-4687.4 mg l-1) and potassium (0.9-42.5 mg l-1).Key words: Physico-chemical parameters, water, Sebkha

Benziane, A

Boualla, N

Derrich, Z

Moussa, K

English

AJOL - African Journals Online

  Vol. 8(2), pp. 114-120, February 2014  DOI: 10.5897/AJEST2013.1569 ISSN 1996-0786 © 2014 Academic Journals http://www.academicjournals.org/AJEST African Journal of Environmental Science and Technology      Full Length Research Paper  Characterization of groundwater quality in  Oran Sebkha basin  BOUALLA Nabila 1*, BENZIANE Ahmed1, MOUSSA Kacem2 and DERRICH Zoubir3  1Department of Civil Engineering, Laboratory Materials, Soil and Thermal, 31000 Oran, Algeria. 2Department of Earth Sciences, Laboratory Geodynamics Basins and Sediment Budget, 31000 Oran, Algeria. 3Department of Chemistry, Laboratory of Physico-Chemical Material/Catalyst/Environment, 31000 Oran, Algeria.  Accepted 9 December, 2013  Growing populations and increasing industrialization causes increase in living standard, which result in decrease in the quality of water and may put stresses on natural waters by impairing both the quality of the water and the hydrological budget. This research aimed at determining the origin of the chemical elements of groundwater from the Oran Sebkha basin. It applied the inverse geochemical modeling to derive the sources of variation in the hydrochemistry. Fifty five (55) water samples were selected from different point in Oran Sebkha basin for sampling purpose in July 2011. Physico-chemical parameters such as pH and electric conductivity were measured in situ. Moreover, chloride, sulfate, alkalinity, calcium, magnesium, sodium, potassium, were measured in the laboratory. Inverse geochemical models of the statistical groups were developed using PHREEQC to elucidate the chemical reactions controlling water chemistry. The inverse geochemical modeling demonstrated that relatively few phases are required to derive water chemistry in the area. In a broad sense, the reactions responsible for the hydrochemical evolution in the area fall into three categories: (1) dissolution of evaporite minerals; (2) precipitation of carbonate minerals; and (3) weathering reactions of silicate minerals. The high values of the physico-chemical parameters of water obtained in the present study sites indicate a variation in the physico-chemical parameters and demonstrated that relatively few phases are required to derive water chemistry in the area. Range of values were found as pH (5.1-7.6), conductivity (720-15820 μS cm-1), chloride (994-7810 mg l-1), sulfate (6.1-112.4 mg l-1), alkalinity (421-19962 mg l-1), calcium (80-680 mg l-1), magnesium (212.4-4525 mg l-1), sodium (124.2-4687.4 mg l-1) and potassium (0.9-42.5 mg l-1).  Key words: Physico-chemical parameters, water, Sebkha.   INTRODUCTION   The availability of good quality water is an indispensable feature for preventing diseases and improving quality of life (Oluduro and Aderiye, 2007). Natural water contains some types of impurities whose nature and amount vary with source of water (Drever, 1988).  Water quality characteristic of aquatic environment arise from a multitude of physical, chemical and biological interactions (Deuzane, 1979). The water bodies, rivers, lakes, dams and estuaries are continuously subject to dyna-mic change with respect to the geological age, geoche-mical characteristics and anthropogenic influences. This is demonstrated by continuous circulation, trans-formation and accumulation of energy and matter through the medium of living things and their activities. The dyna-mic balance in the aquatic ecosystem is upset by human activities, resulting in pollution which is manifested drama-tically as fish kill, offensive taste, odor, color and un-checked aquatic weeds. The objective of the monitoring *Corresponding author. E-mail: nibrasnabila@yahoo.fr.     Boualla et al.          115      Figure 1. Localization of sampling points in the study area.    studies undertaken for water body is to assess variation in water quality. The soundness or validity of the results in the inverse modeling depends on a valid conceptualization of the groundwater system, validity of the basic hydrochemical concepts and principles, accuracy of input data into the model, and level of understanding of the geochemical processes in the area (Güler and Thyne, 2004). Variation in groundwater chemistry is mainly a function of the interaction between the groundwater and the min-eral composition of the aquifer materials through which it moves. Hydrochemical processes, including dissolution, precipitation, ion exchange, sorption and desorption, to-gether with the residence time occurring along the flow path, control the variation in chemical composition of groundwater (Apodaca et al., 2002). The zone of study covers: the great Oran Sebkha basin (with an area of 1878 km²); the Sebkha itself (with an area of 298 km²) and the stretches (over 40 km long and 6 to 13 km wide). The zone is located in the Central Coastal Oran basin and is bounded by: the Djebel Murdjadjo (530 m) in the north, the Mount Tessala (1061 m) in the south, the plain oued Tlelat in the east, and oued Mellah in the west (Figure 1).  The integrated geological study (sedimentology, geo-morphology, tectonic, hydrogeology) determined factors which conditioned its setting up, since the lower-middle Miocene (Burdigalian-Langhian-Serravallian); that emerg-ed in the beginning of the Tortonian age, then it met, and until the Pleistocene under a marine regime that evolved toward a continental regime since the superior Pleisto-cene. The southward swing of the northern area (Murd-jadjo south side) at the Soltanian age would have been the main reason of the Sebkha of Oran endoreism and its subsequently closing (full) with the setting up of the wind accumulations.                                                                                  Legend: 685 690 695 700 705 710 715 72039203925393039353940Al AmriaBoutelélisBrédéahMesserghinHassi El GhallaBouyakourEl KermaHamam BouhdjerTamazourahTafraouiSinking 685 690 695 700 705 710 715 72039203925393039353940Al AmriaBoutelélisBrédéahMesserghinHassi El GhallaBouyakourEl KermaHamam BouhdjerTamazourahTafraouiWell 685 690 695 700 705 710 715 7203920392539303935394012345678 9101112131415161718192021222324252627282930313233343536373839404142434445464748950Spring Oued   116          Afr. J. Environ. Sci. Technol.    Table 1. The physico-chemical parameters of water samples from Oran Sebkha basin.  Parameter  Average Minimum Maximum Standard deviation Median pH 6.9 5.1 7.6 0.4 6.9 EC (µS m-1) 5905.3 720 15820 3303.7 5710 Cl-(mg L-1) 2472.7 994 7810 1180.8 2307.5 SO4-2(mg L-1) 26.1 6.1 112.4 20.3 22 HCO3-(mg L-1) 4764 421 19962 4128 3288 Na+(mg L-1) 863.7 124.2 4687.4 717.7 733.7 K+(mg L-1) 8.6 0.9 42.5 8.4 6.2 Ca2+ (mg L-1) 304.4 80 680 131.9 280 Mg2+ (mg L-1) 1258.8 212.4 4525 920.2 956.4    MATERIALS AND METHODS  In order to characterize the groundwater quality in the dry season, a sampling network was chosen to allow the acquisition of representative data on the spatial and temporal variability (Figure 1). This network covers the entire basin upstream to downstream and consists of a set of points of water wells, boreholes and springs. Water withdrawals were made at low waters. The samples were collected during the period of 04 to 20 July 2011 where comprehensive analyses were performed. The parameters that were measurement are: pH and electrical conductivity (EC) measured in the field using a multi-parameter HANNA (pH meter HANNA instrument HI 9811).  Subsequently, the samples were analyzed in the laboratory for their chemical constituents such as calcium, magnesium, sodium, potassium, chloride, bicarbonate and sulfate. This was achieved using standard methods as suggested by Rodier (1996). Ca2+, Mg2+, HCO3- and Cl- were analyzed by volumetric titrations. Concentrations of Ca2+ and Mg2+ were estimated titrimetrically using 0.05 N EDTA and those of HCO3- and Cl by H2SO4 and AgNO3 titration, respectively. Concentrations of Na+ and K+ were measured using an Ionogram (Model: Ionogram Easy lyte Na/K/Cl, 800 ml, MEDICA 001384-001 R2 Analyser, 12160/12014-05) and that of sulfate by Spectrometer method (Model: Spectrometer UV Optizen 2120 UV). The results were tabled for interpretation. In literature, many different methodologies have been applied to study, evaluate and characterize the sources of variation in groundwater geochemistry. Among these methods is the inverse geochemical modeling in PHREEQC (Parkhurst and Appelo, 1999) based on a geochemical mole-balance model, which calculates the phase mole transfers (the moles of minerals and gases that must enter or leave a solution).   RESULTS AND DISCUSSION  The physico-chemical parameters obtained from analysis of water samples from Oran sebkha basin are presented in Table 1. The groundwater samples of the study area have pH values ranging from 5.1 to 7.6, which indicate that the groundwater is slightly alkaline. The electrical conductivity (EC) values ranged from 720 to 15820 μS cm-1 which is the characteristic of mixed water (Ca-Mg-Cl-HCO3). The gradual increase of conductivity denotes a significantly lateral input of wastewater with higher con-ductivity (Trinh, 2003). The order of abundance of the major cations is Mg ≥ Na ≥ Ca ≥  K and all samples ex-ceeded the desirable limit of Ca, Mg and Cl for drinking water, respectively :75, 50 and 200 mg l-1, but the sulfate concentrations are all below health guidelines (WHO, 1993) (Table 1). In all water samples, a critical look at the results re-vealed that the values of these physico-chemical parame-ters are higher in the basin based on geological position; discharges of industrial wastewater and contamination of the groundwater by seawater were excluded as the source of high concentrations. The quantity of waste in different phases of a natural aquatic system is reflected by the level of hardness, alkalinity, and other physico-chemical parameters. Since the higher values of all these physico-chemical parameters than those obtained could be as a result of washing away of sulfate based fertilizers into the river (Ipinmoroti and Oshodi, 1993; Vogel, 1970).  Inferring the sources of solutes in groundwater using simple massbalance approaches does not provide unequivocal results, a reasonable way of constraining the processes that might influence the major-ion chemistry. The controls on the hydro chemical evolution of ground-water largely depend on the chemistry of the recharging water, water aquifer matrix interaction (cation exchange), or both, as well as groundwater residence time within the aquifer (Garrels and MacKenzie, 1971). Three general processes that contribute to the generation of solutes in groundwater are: evaporate dissolution, carbonate dissolution and silicate weathering (Garrels and MacKenzie, 1971). The chemistry of the evolving water depends not only on the bulk chemistry of the matrix, but also on the rate of weathering. Meybeck (1987) reported that weathering rates of evaporates and carbonates are up to 80 and ~12 times, respectively, faster than silicate weathering rates. Hence, even relatively minor proportions of carbonates and evaporates can significantly influence water chemistry. The study of the Ca2+/Mg2+ (méq L-1) ratio of ground-water from the area of study suggests the dissolution dolomite present in the alluvium (Figure 2). That is, if the ratio Ca2+/Mg2+ = 1, dissolution of dolomite should occur, whereas a higher ratio is indicative of greater calcite con-  Boualla et al.          117      Figure 2. Sample number versus Ca2+/ Mg2+.      Table 2. Saturation indices of the water samples from Oran Sebkha basin calculated by PHREEQC.  Phase  Stoichiometry Average Anhydrite CaSO4 -2.19 Aragonite CaCO3 0.84 Calcite CaCO3 0.98 Dolomite  CaMg(CO3)2 2.87 Gypsum  CaSO4:2H2O -1.98    tribution (Maya and Loucks, 1995). The points are located below the line (Ca2+/Mg2+ =1) indicating the dissolution of dolomite. The samples have a ratio between 0.03 and 0.72 indicating the dissolution of dolomite. Dissolved carbonates (calcite and dolomite) occur predominantly in the form of HCO3-, due to the pH range. The solubility of calcite and dolomite is largely controlled by CO2 fugacity and pH, according to the reactions:  CaCO3 + CO2(g) + H2O=Ca2+ + 2HCO3-                                       (1)                                                                        Ca1-xMgxCO3 + CO2 (g) + H2O = (1-x) Ca2++ xMg2+ + 2HCO3-                                                                      (2)  The plot of Ca2++ Mg2+ versus SO4-2 + HCO3- will be above the 1:1 line if the dissolutions of calcite, dolomite, anhydrite and gypsum are the dominant reactions in a system (Maya and Loucks, 1995). Ion exchange tends to shift the points to left due to an excess of Ca2++ Mg2+ (Cerling et al., 1989; Fisher and Mulican, 1997; McLean and Jankowski, 2000). If reverse ion exchange is the process, it will shift the points to the right due to a large excess of SO42-+ HCO3- over Ca2++ Mg2+. The plot of Ca2++ Mg2+  versus SO42-+ HCO3- (Figure 2) shows that the all samples  are located in the right side due to an excess of SO4-2+ HCO3- (Belkhiri et al., 2010). A Na (méq L-1)-normalized Ca2+ (méq L-1) versus HCO3- (méq L-1) and plot Mg2+ (méq L-1) (Figures 3, 4 and 5) (Gaillardet et al., 1999) shows that the three group samples range from being influenced by silicate wea-thering to carbonate dissolution. The relation between Na-normalized Ca2+, HCO3- and Mg2+ shows that although most of the Mg may have been derived from carbonate dissolution, some have a silicate source (Belkhiri et al., 2010).  The saturation indices of some of the common mineral phases is presented in Table 2, which clearly shows that the groundwater is generally supersaturated with respect to most of the carbonate and silicate phases and is most probably responsible for the composition of the ground-water (Belkhiri et al., 2010). The results of saturation calculations show that all the points are under saturated with anhydrite and gypsum, halite mineral phases are minor or absent in the area, suggesting that their soluble components Na+, Cl-, Ca2+ and SO42- concentrations are not limited by mineral equilibrium. In contrast, aragonite, calcite and dolomite reach saturation as groundwater chemistry evolves along the groundwater flow paths. The groundwater in the studied area evolves from less saline Ca-g-HCO3 water to blended Mg-Ca-HCO3-Cl water to brackish Mg-Ca-Cl-HCO3 water along the topographic flow path inverse geochemical modeling along ground-water flow paths indicating the dissolution of evaporite minerals, precipitation of carbonate minerals and weathe-ring reactions of silicate minerals (Table 1 and Figure 6)     Ca/Mg 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00   118          Afr. J. Environ. Sci. Technol.      Figure 3. Ca2++ Mg2+versus SO4-2+ HCO3-.      Figure 4. Na-normalized Ca2+ and HCO3- (HCO3/ Na) (méq L-1/ méq L-1).      Ca2++ Mg2+(méq∕l)   HCO3/Na 100.00  10.00  1.00  0.000  0.01 0.01                              0.10                              1.00                          10.00                        100.00 Ca/Na 1 :1   Boualla et al.          119      Figure 5. Na-normalized Ca2+ and Mg2+.      Figure 6. Piper diagram showing groundwater classification (Piper, 1994).       Mg/Na 100.00  10.00  1.00  0.000  0.01 0.01    0.02   0.04   0.08    0.16   0.32   0.64     1.28    2.56   5.12   10.24 Ca/Na  120          Afr. J. Environ. Sci. Technol.    (Belkhiri et al., 2010).    Conclusion  In conclusion, the water quality is a significant aspect of determination of the water body status. The parameters examined in the scope of this thesis were subjected to variety of spatial trends. The results of this study show that the groundwater in the studied area evolves from less saline Ca-Mg-HCO3 water to blended Mg-Ca-HCO3-Cl water to brackish Mg-Ca-Cl-HCO3 water along the topographic flow path. The analysis indicates that the water of Oran sebkha basin is characterized by moderate alkalinity in the investigated period. In addition to this, it important that bacteriological assessment of water from these different wells be carried out to sure if the water is safe for drinking and other domestic applications.   REFERENCES  Apodaca LE, Jeffrey BB, Michelle CS (2002). Water quality in shallow alluvial aquifers, Upper Colorado River Basin, Colorado, 1997. J. Am. Water Res. Assoc. 38 (1):133-143. Belkhiri L, Boudoukha A, Mouni L, Baouz L (2010).   Application of multivariate statistical methods and inverse geochemical modeling for characterization of groundwater - A case study: Ain Azel plain (Algeria).  Cerling TE, Pederson BL, Damm KLV (1989). Sodium-calcium ion exchange in the weathering of shales: implications for global weathering budgets. Geology 17:552-554.  Deuzuan J (1979). Handbook of drinking water quality. Indiana Univ. Press. pp. 3-17. Drever JI (1988). The Geochemistry of Natural Waters. Prentice-Hall, Upper Saddle River, NJ. Fisher RS, Mulican WFIII (1997). Hydrochemical evolution of sodium-sulfate and sodium-chloride groundwater beneath the Northern Chihuahuan desert, Trans- Pecos, Rexas, USA. Hydrogeol. J. 10(4):455-474. Gaillardet J, Dupre B, Louvat P, Allegre CJ (1999). Global silicate weathering and CO2 consumption rates deduced from the chemistry of large rivers. Chem. Geol. 159:3-30. Garrels RM, MacKenzie FT (1971). Evolution of Sedimentary Rocks. Norton, New York.                      Güler C, Thyne GD (2004). Hydrologic and geologic factors controlling surface and Groundwater chemistry in Indian wells-Owens Valley area, southeastern California, USA. J. Hydrol. 285:177-198.  Ipinmoroti K, Oshodi O (1993). Determination of Trace Metals in fish, associated Wanted and Soil Sediments fresh fish ponds. Discovery innovates 5:138. Maya AL, Loucks MD (1995). Solute and isotopic geochemistry and groundwater flow in the Central Wasatch Range, Utah. J. Hydrol. 172:31-59. McLean W, Jankowski J (2000). Groundwater quality and sustainability in an alluvial aquifer, Australia. In: Sililo, et al. (Ed.), Proc. XXX IAH congress on Groundwater: Past Achievements and Future Challenges. Cape Town South Africa 26th November-1st December 2000. AA Balkema, Rotterdam, Brookfield. Meybeck M (1987). Global chemical weathering from surficial rocks estimated from river dissolved loads. Am. J. Sci. 287:401-428. Oluduro AO, Adewoye BI (2007). Efficiency of moringa Oleifera Sead extract on the microflora of surface and ground water. J. Plant Sci. 6:453-438. Parkhurst DL, Appelo CAJ (1999). User's Guide to PHREEQC (Version 2)-A Computer Program for Speciation, Batch-Reaction, One-Dimensional Transport, and Inverse Geochemical Calculations.  Piper AM (1994). A graphic procedure in geochemical interpretation of water analyses. Am. Geophys. Union Trans. 25 :914-923. Rodier J (1996). L’analyse de l’eau, eaux naturelles, eaux résiduaires, eau de mer. 8e édition Dunod, Paris. Trinh AD (2003). Étude de la qualité des eaux d’un hydro système fluvial urbain autour de Hanoi (Vietnam); Suivi expérimental et modélisation. Thèse de doctorat de Université Joseph Fourier - Grenoble 1 (France) et Centre National des Sciences et de la Technologie (Vietnam). United States Geological Survey, Water Resources Investigations Report 99-4259, Washington, DC. p. 326. Vogel I (1970). A text book of inorganic analysis published by Harley and Sons, 4th Ed. p.148. WHO (1993). Guideline for drinking water quality 2nd Ed. Recommendation. World Health Organization general 1:30-113.         

Characterization of groundwater quality in Oran Sebkha basin

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Characterization of groundwater quality in Oran Sebkha basin

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