Mapping of Groundwater Facies using anion Geochemistry in Angware Area, Jos Northcentral Nigeria

Abstract

The use of anion geochemistry in mapping groundwater facies in Angware area was discussed. The objective of this work is to specially use only anion species to identify the facies present in the groundwater and the processes responsible for the modification of water chemistry in the area. 20 water samples were collected and analyzed using DR 2000 spectrophotometer and titrimetric method. The results indicated that pH range from 5.8 – 7.6 with an average of 6.5 while HCO3 -, SO4 2- and Cl- reveal values ranging from 19.6 mg/l – 318.4 mg/l, 0.1 mg/l – 6.0 mg/l and 1.1 mg/l – 28.4 mg/l with mean values of 74.8 mg/l, 1.4 mg/l and 7.5 mg/l, respectively. CO3 2- was not detected in all the samples due to acidic to neutral pH condition. Based on the mean values, the anions were in the order of abundance as HCO3 -> Cl-> SO4 2-. The study identified Bicarbonate-Chloride-Sulphate facies as the only facies-type which is an indication of recently recharged groundwater with limited rock-water interaction. The plot of Cl-/Cl- + HCO3 - against LogTDS revealed precipitation induced chemical weathering along with dissolution of rock forming minerals.