Geophysical and Hydrochemical Studies to Map Saltwater Infiltration into Freshwater aquifers: A case study of Ikoyi, Lagos State, Nigeria
Abstract
A total of three electrical imaging lines were measured using the Wenner configuration. And a total of fifteen VES was carried out within the area of investigation and six water samples was collected. The results were presented as profiles, model sections, inverted sections and tables. Interpretations of these results involve both qualitative and quantitative deductions from 1D and 2D geoelectric models and laboratory analysis for the water analysis. The VES data were processed by partial curve matching to generate the 1st order geoelectric parameters and inverted in 1D using the WinResist. The 2D resistivity data were processed by inversion using the DIPROFWIN to generate the 2D resistivity section across each traverse while the water samples were taken to the laboratory for comprehensive analysis. The 2D resistivity structures reveal the lateral and the vertical subsurface information with resistivity values ranging from 0.130 to 4741 Ωm. The resistivity values are representative of the clay, clay (saline), clayey sand (saline), clayey sand and sand. From the quantitative interpretation five to six distinct layers were identified. The layers are: topsoil, clayey sand, clay, saline clayey sand, saline clay and sand. The resistivity of the topsoil varies from 38.2 Ωm to 155.3 Ohm-m. The resistivity of the sand varies from 100.8 Ωm to 115.8 Ωm. The resistivity of clayey sand varies from 56.6 Ωm to 90.1 Ωm. The resistivity of clay varies from 12.7 Ωm to 41.2 Ωm. The resistivity of the saline layer (saline clayey sand/clay) varies from 2.1 Ωm to 51.2 Ωm. The depth of saline clay interface varies from 25.7 m to 72.6 m. The depth to the saline clayey sand interface varies from 25.7 - 72.6 m. The chemical analysis of water samples showed that the pH varies from 7.05 to 8.42, total dissolved solids vary from 1786 to 2116 mg/L and electrical conductivity varies from 2106 to 2656 µS/cm. The anions and cation concentrations such as Ca2+, Mg2+, Na+, K+, Cl- and HCO3- ranges from 158 to 185 mg/L, 36 to 48 mg/L, 222 to 287 mg/L, 3.2 to 3.8 mg/L, 10.86 to 20.87 mg/L and 2.33 to 3.88 mg/L respectively. The ratio of Cl/HCO3- ion ranges from 4.05 to 7.67. The interpreted results show saline water intrusion where they occur in different part of the area investigated. The results showed the effectiveness and usefulness of electrical resistivity method in mapping saline water intrusion problem in coastal areas. However, it is necessary to carry out integrated geophysical surveys involving electrical resistivity and induced polarization methods prior to drilling in the study area.
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2. Batayneh, A.T. (2006). Use of electrical resistivity methods for detecting subsurface fresh and saline water and delineating their interfacial configuration: a case study of the eastern Dead Sea coastal aquifers. Jordan Hydrog J 14:1277–1283
3. Ben Moussa, A., Zouari, K. and Marc, V. (2011). Hydrochemical and isotope evidence of groundwater salinization processes on the coastal plain of Hammamet-Nabeul, north-eastern Tunisia. Phys Chem Earth 36(5–6):167–178.
4. Bhattacharya, A.P.K. and Patra, H.P. (1968). Direct Current Geoelectric Sounding: Principles and Interpretations: Methods of Geochemistry and Geophysics. Elsevier Publishing Company, Amsterdam. 135.
5. Bouderbala, A. (2014). Groundwater salinization in semi-arid zones: an example from Nador plain (Tipaza, Algeria). Environmental Earth Sciences, 73(9), 5479–5496. doi:10.1007/s12665-014-3801-9
6. Capaccioni, B., Didero, M., Paletta, C. and Didero, L. (2005). Saline intrusion and refreshening in a multilayer coastal aquifer in the Catania Plain (Sicily, Sthohern Italy): dynamics of degradation processes according to the hydrochemical characteristics of groundwaters.
7. Chitea, F., Georgescu, P. and Ioane, D. (2011). “Geophysical detection of marine intrusions in Black Sea coastal areas (Romania) using VES and ERT data”, Geo-Eco-Marina, Vol. 17, pp. 95-101.
8. Choudhury, K., Saha. D.K. and Chakraborty, P. (2001). Geophysical study for saline water intrusion in a coastal alluvial terrain. Journal of Appl. Geophysics 46:189–200
9. Cimino, A., Cosentino, C., Oieni, A. and Tranchina, L. (2008). A geophysical and geochemical approach for seawater intrusion assessment in the Acquedolci coastal aquifer (Northern Sicily). Environ Geol55:1473–1482
10. Dahlin, T. and Zhou, B. (2004). A numerical comparison of 2D resistivity imaging with ten electrode arrays. Geophys. Prospect, 52:379–398
11. El Moujabber, M., BouSamra, B, Darwish, T. and Atallah, T. (2006). Comparison of different indicators for groundwater contamination by seawater intrusion on the Lebanese Coast. Water Resour. Manag. 20:161–180
12. Himi M., Stitou J., Rivero L., Salhi A., Tapias J.C., Casas A. (2010).“Geophysical surveys for delineating salt water intrusion and fresh water resources in the OuedLaou coastal aquifer Near Surface” , 16th European Meeting of Environmental and Engineering Geophysics, Abstracts volume, Switzerland.
13. Kalisa, I., Mugerwa, T., Ndikumana, Jean de D., Uwamungu, P., Munganyinka, J.P., Hishamunda, V. and Nsengimana, S. (2016). An Integrated Study on Seawater Intrusion using Geoelectrical Resistivity and GIS Techniques in Part of Pondicherry, South-East Coast of India. International Journal of Innovative Research in Science, Engineering and Technology, 5(1).
14. Khublaryan, M.G., Frolov, A.P. and Yushmanov, I.O. (2008). Seawater Intrusion into Coastal Aquifers. Water Resour 35(3):274–286
15. Kouzana, L., Benassi, R., Ben Mammou, A. and Sfar felfoul, M. (2010). Geophysical and hydrochemical study of the seawater intrusion in Mediterranean semi-arid zones. Case of the Korba coastal aquifer (Cap-Bon, Tunisia). J Afr Earth Sc 58:242–254
16. Loke. M.H. and Barker, R.D. (1996). Rapid least-squares inversion of apparent resistivity pseudosections by a quasi-Newton method. Geophys Prospect 44:131–152
17. Loke, M.H. and Dahlin, T. (2002). A comparison of the Gauss-Newton and Quasi- Newton methods in resistivity imaging inversion. J Appl Geophys 49:149–162
18. Loke, M.H., Acworth, I. and Dahlin. T. (2003). A comparison of smooth and blocky inversion methods in 2D electrical imaging surveys. Explor Geophys 34:182–187
19. Murat, R.C. (1972). Stratigraphy and Paleography of the Cretaceous and lower Tertiary in Southern Nigeria, Afr. Geol., U.I. press, p. 17.
20. Milnes E, Renard, P. (2004). The problem of salt recycling and seawater intrusion in coastal irrigated plains: an example from the Kiti aquifer (Southern Cyprus). J Hydrol 288:327–343
21. Milson, J. (1996). Field Geophysics. John Wiley and Sons Limited, West Sussex, England, 103.
22. Mondal, N.C., Singh, V.P. and Ahmed, S. (2013). Delineating shallow saline groundwater zones from Southern India using geophysical indicators. Environ Monit Assess 185:4869–4886
23. Mondal, N.C., Singh, V.P., Singh, V.S. and Saxena, V.K. (2010). Determining the interaction
24. between groundwater and saline water through groundwater major ions chemistry. J Hydrol 388:100–111.
25. Nielsen, L., Jørgensen, N.O. and Gelting, P. (2007). Mapping of the freshwater lens in a coastal aquifer on the Keta Barrier (Ghana) by transient electromagnetic soundings. J Appl Geophys 62:1–15.
26. Omatsola, M.E., and Adegoke, O.S. (1981). Tectonic Evolution and Cretaceous Stratigraphy of the Dahomey Basin Journal of Mining and Geology. 18, 130-137.
27. Pulido-Leboeuf, P. (2004). Seawater intrusion and associated processes in a small coastal complex aquifer (Castell de Ferro, Spain). Appl Geochem 19:1517–1527
28. Ritz, M., Parisot, J.C., Diouf, S., Beauvais, A., Dione, F. and Niang, M. (1999). Electrical imaging of lateritic weathering mantles over granitic and metamorphic basement of eastern Senegal, West Africa. J. Appl Geophys 41:335–344
29. Schoenleber, J.R. (2005). Field Sampling Procedures Manual. Department of environmental protection, New Jersey, p 574
30. Slansky, M. (1962). Contributional etude Geological du Basin sedimentative corfell all Dahomey at du too Bearaeu du Kuchercher Geologue at Mounever memoir, pp. 11-12.
31. Steyl, G. and Dennis, I. (2010). Review of coastal area aquifers in Africa. Hydrogeology Journal, 18(1), 217–225.
32. Store, H., Storz, W. and Jacobs, F. (2000). Electrical resistivity tomography to investigate geological structures of earth’s upper crust. Geophys Prospect 48:455–471
33. Tosin, A. O., Ayokunle, A. A., Gbenga, M. O., Adebowale, O. A. and Kola, A. A. (2015). Geophysical and Hydrochemical Investigation of a Municipal Dumpsite in Ibadan, Southwest Nigeria. Journal of Environment and Earth Science, 5(14).
34. VanNorstrand, R. and Cook, K.L. (1966). Interpretation of resistivity data. USCGS Professional Paper-499, US Govt. Printing Office, Washington
35. Whiteman, A. (1982). Nigeria: Its Petroleum Geology resources and potential, Graham and Trotman Ltd. 1: 166.
36. WHO, 2017. Water Quality and Health: Review of Turbidity Information for Regulators and Water Suppliers. WHO, Geneva. www. who.int/entity/water sanitation health/ publications/turbidity technical-brief/en/ index.html (accessed March 2017).
37. Zouhri, L., Carlier, E., Ben Kabbour, B., Toto, E.A., Gorini, C. and Louche, B. (2008). Groundwater interaction in the coastal environment: hydrochemical, electrical and seismic approaches. Bull Eng Geol Environ 67:123–128.
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