Characterization by factor analysis of the chemical facies of groundwater in the deltaic plain sands aquifer of Warri, western Niger delta, Nigeria

This paper examines the hydrochemical facies of groundwater present in the Deltaic Plain Sands aquifer of Warri and its immediate environs, maps their areal distribution and attempts to explain the controlling processes responsible for the various facies. 60 water samples were collected from wells tapping the Deltaic Plain Sands aquifer of Warri and environs and analyzed for various parameters including pH, total dissolved solids (TDS), K, Na, Ca, Mg, Cl, HCO3 and SO4 after standard procedures. The data obtained were subjected to R-mode factor analysis. Three factors were extracted. Factor 1 includes K, Na, Cl, and EC and reflects the signature of saline water incursion resulting from seepages into the aquifer of water from the tide-influenced River Warri. Factor 2 has high loading values of Mg, Ca, HCO3 and pH and represents the processes of natural rainwater recharge and water-soil/rock interaction. Factor 3 includes SO4 and can be related to the dissolution of sulphides from interstratified peat within the geological formation, heavy vehicular activity and the petroleum refining process in the town. The areal distributions of the various factor scores indicate that factors 1 and 2 are enhanced close to the banks of River Warri and decreases away from them. A broad zone of groundwater interaction (mixing) between water species represented by factors 1 and 2 is thus created towards the riverbanks. The implication of this is that ionic concentration in the water decreases away from the banks of the river an indication that the quality of groundwater improves away from the river. Factor 3 is enhanced in the southeastern portion of the town where it is deemed to be caused by the dissolution by groundwater of sulphur bearing minerals within the geological formaton, and also in the central and northwestern portions of the town were it could be related to the rain-dissolution of sulphur bearing compounds from gaseous emanations arising from vehicles and the petroleum refining process respectively, which eventually as acid-rain recharges aquifers in the vicinity. This paper demonstrates the effectiveness of factor analysis in evaluating hydrochemical processes in coastal and industrial areas