SIMULATION OF HEAVY METALS MOVEMENT AND CHANGE IN CONCENTRATION IN SHALLOW UNCONFINED AQUIFER IN NORTH CENTRAL NIGERIA USING VISUAL MOFLOW AND MT3DMS

Abstract

Shallow groundwater is a major water source for rural people in Minna, a rapidly growing city in North-central Nigeria. However, indiscriminate dumping and poor poultry waste management in and around the city have threatened the quality of this water source. Visual MODFLOW was used to study the loading, dynamics fate and transport of some heavy metals in Minna shallow aquifer while MT3DMS was used to predict the concentration of the heavy metals in one, three and five years’ time. Conceptual model approach was employed for the simulation with the model domain discretized into 50cells each in x and y directions. Results showed that the whole aquifer was strongly contaminated with arsenic, copper and Zinc. This was presented as colour shading by visual MODFLOW. Initial concentrations of arsenic copper and zinc were 0.74mg/L, 8.43mg/L and 11.63mg/l respectively as against 0.01mg/l, 2.00mg/L and 5.00 mg/L recom-mended as maximum allowable contamination (MAC) for drinking water by WHO. MT3DMS predicted a progressive reduction in heavy metals concentration. For instance, a reduction in value to 0.60 mg/L, 7.51 mg/L and 4.20 mg/l were predicted for arsenic, zinc and copper re-spectively over five-years period. The study also revealed that the polluted shallow aquifer in Minna can be cleaned up of these heavy metals after some years.