FactSage Modelling of Pb and Ni Speciation in Surface Water from Woji Creek, Rivers State, Nigeria

Abstract

The present study is designed to use FactSage version 7.3 to simulate and predict the ionic speciation of lead (Pb) and nickel (Ni) in surface water sampled from Woji creek in Rivers State, Nigeria. Along the 3 km stretch (stations 1 to 5) of Woji creek, in-situ records were taken for temperature, pH and electrode potential (Eh); surface water samples to be assessed for Pb and Ni were collected in sterile bottles. Along the creek, surface water Eh is in the order: station 2 > station 4 > station 5 > station 3 = station 1, with mean value of Eh as 140 ± 20 mV. Surface water pH was close to neutral, and in line with: station 4 > station 2 > station 5 > station 1 > station 3; with 6.81 ± 0.13 as the mean value of pH. The trend of temperature values was recorded as: station 1 > station 2 = station 3 = station 4 > station 5; with the mean value deduced to be 25.6 ± 0.4. Mean concentration of Pb and Ni across the creek were 0.92 ± 0.27 mg/l and 0.46 ± 0.23 mg/l respectively. Pb species exists predominantly in the forms: Pb6(OH)84+(aq) (45%), Pb4(OH)44+(aq) (45%). Other forms of Pb present in the surface water are PbO(s) (5%), PbO2(s) (4%) and Pb2+(aq) (1%). NiO(s) had the highest proportion of Ni in the surface water (67%), followed by Ni(OH)2(s) (30%) and Ni2+(aq) (3%). The predicted metallic species could possibly be sorbet to particulates; thereby increase their chances of bioavailability and subsequent ingestion by fishes and other aquatic organisms. This will in turn influence their bioaccumulation via food chain and increase the tendency of risk impact on man and aquatic ecosystem.