Mapping, Characterization and Dispersion of Metallic Pollutants within a Catchment of Illegal Gold Mining Activities in Ghana

Abstract

The illegal gold mining activities prevalent in most part of Ghana have caused substantial havoc to the environment especially water bodies which serve as sources of water for domestic, industrial and agricultural purposes. The Ghana Water Company Limited (GWCL) recently shut down their water treatment plant due to the extreme pollution and high cost of treatment. This study focusses on the impact of mining activities on water quality of the affected water bodies, to assess the level of pollution of the river sediments and the extent of dispersion of the heavy metallic pollutants and to map out areas within the Konongo Municipality where illegal mining activities are prevalent. In this regard, both water and sediment samples from two rivers namely; Owerri and Asuokofi in Konongo (in the Asante Akim Central Municipality) were collected at different locations and analysed using Flame Atomic Absorption Spectrometry (FAAS) to assess the concentrations and dispersions of metallic pollutants. Geographical Positioning System (GPS) coordinates of these sample locations were also taken for mapping the sampling points and area. Four different metals; mercury (Hg), Lead (Pb), Arsenic (As) and Cadmium (Cd) were analysed. For sediments, the mean levels of Pb, Hg, As and Cd for the owerri river were found to be 52.2±2, 0.3±0.5, 492±365 and 1.7±2.0 mg kg1 respectively; whilst those for Asuokofi river were 12±0.7, 2.7±0.4, 21.2±13.5 and 1.6±0.4 mg kg1 respectively. The mean levels of Pb, Hg, As and Cd for water of the owerri river are respectively 2.5±3.7, 0.20±0.4, 0.28±0.2 and 3.1±0.4 mg L1; whilst those for Asuokofi river were 8.2±1.3, 2.3±1.8, 25.4±22.2 and 0.45±0.7 mg L1 respectively. Comparing these levels with the WHO standards for water discharges, these concentrations far exceeded the recommended values. This will impact negatively on the quality of both rivers with dire consequences since they serve as the main raw water resource for drinking water production. Samples of sediments and water from the upstream of these rivers where no activity of alluvial mining is taken place were recorded and they showed lower levels of these metals. It can therefore be concluded that the activities of alluvial gold mining in the study area impacts negatively on both the quality of water in the river and the sediments thereof.