Geoenvironmental Investigation of Some Physical and Chemical Constituents of Ground Waters in of Sapele and Environs, Western Niger Delta, Nigeria

Abstract

Hydrogeochemical studies have been carried out in parts of Sapele and Warri Local Government Areas of Delta State in order to determine the different hydrogeochemical facies and understand the groundwater flow regime and its effect on the chemical composition of the groundwater so as to evaluate the anthropogenic effects on groundwater quality in the study area. Twenty-five (25) water samples were taken from Sapele (18) and Warri (7) in one liter plastic cans with temperature, pH, electrical conductivity and Total Dissolved Solids (TDS) determined in-situ. The samples were then taken to the laboratory where the analyses were done using the Varian 220 flame atomic absorption spectrophotometer. Salinity and chloride in water was carried out in accordance with the American Petroleum Institute (API-RP) 45. Phosphate, Nitrate, Sulphate, Calcium, Potassium, Sodium, Magnesium and Ammonium were all determined in accordance with the American Public Health Association (APHA) 425C,427C and 417C.

The analyses carried out indicated the presence of chloride ion as the dominant parameter. Chloride shows a negative correlation with all other parameters thus indicating that its source is from surface saline waters close to those areas with high chloride concentrations. The presence of ammonia in such high concentrations and its strong positive correlation with phosphate supports that its source is as a result of pollution from sewage. The positive correlation of phosphate, sulphate, nitrate and TDS also indicate pollution from sewage. GPS readings and computation of several hydrogeological parameters showed a SW direction of groundwater flow for Sapele and a SE flow direction for Warri. The presence of ammonium at levels higher than geogenic (geologically related processes) levels is a strong indicator of fecal pollution. The groundwater in the area is mostly acidic with high chloride concentrations.Contamination from anthropogenic sources is mainly as a result of waste waters from brines released as by-products of oil exploration activities and leaky septic tanks. The presence of chloride is from the proximity of areas that lie southward towards the Atlantic Ocean and the fact that water doesn't mix excessively at greater depths but the chloride levels are still within accepted standards for domestic use. Domestic wastes from septic tanks and improper waste disposal are the main sources of ammonium in the groundwater of the study area, and this reduces the groundwater quality in the area markedly.