Environment and Pollution; Vol. 4, No. 1; 2015 ISSN 1927-0909 E-ISSN 1927-0917 Published by Canadian Center of Science and Education 37 Urbanization and Major Ion Hydrogeochemistry of the Shallow Aquifer at the Effurun - Warri Metropolis, Nigeria Irwin Anthony Akpoborie, Kizito Ejiro Aweto & Oghenero Ohwoghere-Asuma 1 Department of Geology, Delta State University, Abraka, Nigeria Correspondence: Irwin Anthony Akpoborie, Delta State University, Nigeria. E-mail: tony.akpoborie@gmail.com Received: October 29, 2014 Accepted: November 10, 2014 Online Published: December 29, 2014 doi:10.5539/ep.v4n1p37 URL: http://dx.doi.org/10.5539/ep.v4n1p37 Abstract Results from chemical analyses of forty dug well water samples in the Effurun-Warri metropolis show that mean pH is 7.1 and mean TDS is 193 mg/l. Representative mean levels of cation occurrence include Ca, Mg, Na and K at 6.13mg/l, 4.09 mg/l, 4.89 mg/l and 3.37 mg/l respectively. Mean anion concentration for bicarbonate was 8.20mg/l, 1.27mg/l for sulphate and 23.74mg/l for chloride. Physical and chemical parameters are thus well below WHO and Standard Organization of Nigeria drinking-water quality standards. Piper diagram plots of the data indicate that ground water is predominantly Ca+Mg+Na Chloride facie and that mixing and ion exchange processes control the dominant cation in space and thus at each specific locality. Leachates from the many, widely distributed and unregulated landfills and dumpsites have been identified as possibly the principal sources of major ion loading to groundwater. The ubiquitous onsite sewage treatment soak away pits also contribute major ions to groundwater. These two sources are thus accountable for any observed local spikes in groundwater chloride content rather than sea water intrusion as had been previously suggested. Keywords: urban water, leachates, major ions, dump sites, ion exchange, Niger Delta, Benin Formation 1. Introduction The quality of ground water and surface water in the Effurun - Warri metropolis, the densely populated hub of the oil and gas industry in the western Niger Delta, Figure 1, Figure 2 has attracted considerable research interest because in the absence of reliable formal public water supply systems the majority of an estimated population of up to one million residents (Babatola & Uriri, 2013), commerce and industry rely on self-supplies from dug wells and shallow boreholes. Thus, potential contamination of shallow groundwater with heavy metals from four primary sources have been suggested: oil and gas and related industry activities (Aremu, Olawuyi, Metshitsuka, Sridhar, & Oluwande ,2002; Nduka & Orisakwe, 2007, 2009; Emonyan, Akporhonor & Akpoborie, 2008; Etchie, Etchie & Adewuyi, 2011), leachates from unregulated garbage dumps (Akudo, Ozulu & Osogbue , 2010), road wash and storm water runoff (Egboh, Nwajei & Adaikpoh, 2000) and soils (Iwegbue, Nwajei, Ogala, & Overah, 2010). In addition, Olobaniyi and Owoyemi (2004; 2007) have also suggested possible chloride enrichment of the underlying aquifer by recharge from the tidal Warri River and its tributary creeks and argue that heavy ground water abstractions in parts of the city are potentially inducing sea water intrusion from the Atlantic Ocean. The influences of all these factors on the major element geochemistry and the quality of groundwater are not well understood. Furthermore, published research on the chemistry of water from the area has usually been devoid of geolocated data points and this has hitherto severely limited the identification and closer examination of any inherent spatial and possible temporal trends in the occurrence of chemical constituents in groundwater. Thus the objective of this paper is to provide a description of the major element geochemistry of groundwater using geo-referenced data and against which future evaluations and trends in this highly vulnerable and rapidly expanding urban environment may be compared. The results reported herein constitute part of a groundwater evaluation study, partial results from which have been reported by Akpoborie, Uriri and Efobo (2014). 1.1 Study Area 1.1.1 Climate, Physiography and Drainage The Effurun-Warri metropolis lies roughly between latitude 5 0 30’N - 5 0 45N and longitude 5 0 15’E - 5 0 50’E, Figure 2 and enjoys a hot (23 0 C - 37 0 C) and humid (Relative Humidity, 50 - 70 per cent) equatorial climate with