HEAVY METALS CONTAMINATION AND DISTRIBUTION IN SURFACE WATER AND SEDIMENT OF THE ABOABO STREAM, AHAFO REGION, GHANA

Abstract

Activities of illegal small-scale miners promote continual introduction of wide pollutants into the Aboabo stream. Their toxicity poses health threats to the inhabitants of Krapoo village in the Ahafo Region, Ghana. The study assesses the impacts of illegal small-scale mining activities on the water quality of the stream. Levels of physico-chemical and microbiological parameters were determined using standard methods. Samples of sediment, water and plant were acid-digested with aqua-regia. Total Arsenic and Total Cadmium were analysed using Flame Atomic Absorption Spectrophotometer (FLAAS) whiles Total Mercury was analysed using Cold Vapour Atomic Absorption Spectrophotometer (CV-AAS). Turbidity, faecal coliforms and E-coli readings exceeded permissible limit of 5NTU and 0MPN/100ml respectively by Ghana’s Environmental Protection Agency (GS 1212) and World Health Organisation (WHO). Temperature, Electrical Conductivity and pH values were within the limit of <30oC, 1500μs/cm and 6.5-85 respectively at both seasons. Total suspended solids readings at the midstream were higher than the permissible limit. However, levels of total dissolved solutes and dissolved oxygen recorded, were below the limit. The sediments were also heavily polluted with Mercury, Arsenic and Cadmium. Alchornea cordifolia, Chromolaena odorata and Spigella anthelmia growing within the stream were taken to assess their efficiency in removing the heavy metals from the stream. It was observed that the plants species had bioaccumulation factor (BF) greater than 1 for cadmium. Alchornea cordifolia was the only plant with BF greater than 1 for mercury. The plants species are potential hyper accumulators for mercury and cadmium hence are suitable for phytoremediation.