Heavy metal contamination in stream water and sediments of gold mining areas of South Western Nigeria

This study assessed the seasonal variation in heavy metal contamination of stream water and sediments in the gold mining area of Atakunmosa West local Government, Osun State, Nigeria. Twelve villages of prominence in illegal gold mining were selected for the study covering dry and wet seasons of 2012. Stream water and sediment samples were randomly sampled for both seasons. Samples were analyzed with atomic absorption spectrometric method (AAS) and X-ray fluorescence spectroscopy (XRF) for Cd, Zn, Pb, Fe, Zn, Mn, Cu and As. The trend observed for the metals analyzed in the stream water for both seasons are Cu > Zn > Fe > Cd > Pb > As. In stream sediments, higher mean concentration values were generally recorded in the dry season than in wet season. Four metals (Cd, Pb, Cu and Fe) in stream waters and sediments were found to be higher than allowed limits both by the World Health Organisation (WHO, 2004) and the Nigerian standard for drinking water quality (NSDWQ, 2007) in some villages for both seasons, attesting to pollution of the environment resulting from the mining operations and this call for concern. Key words : Heavy metal, surface water, sediments, atomic absorption spectrometry (AAS), x-ray fluorescence spectroscopy (XRF), gold mining.