Impact of Gold Mining Activities on the Birim River in the Akyem Abuakwa Area in the Eastern Region of Ghana.

Abstract

This study was conducted to assess heavy metal contamination (Hg, Fe, Ni, As, Mn, Pb, Cd, Zn) in water and sediment samples from the Birim River in the Akyem Abuakwa Area. Water and sediment samples were taken from ten different Sites within the Akyem Abuakwa area in September 2015 (wet season) and January 2016 (dry season). Heavy metal concentrations were determined using atomic absorption spectrophotometer (AAS) equipped with cold vapour (CVAAS) for total mercury. In the wet season, mean concentrations of heavy metals in the water samples were 0.47 µg/L (Hg), 1.75 mg/L(Fe), 0.03 mg/L (Ni), 0.01 mg/L (As) , 0.40 mg/L (Mn), 0.02 mg/L (Pb), 0.02 mg/L (Cd) and 0.18 mg/L (Zn) while in the dry season, the mean concentrations were 0.34 µg/L (Hg), 1.28 mg/L (Fe), 0.05 mg/L (Ni), 0.01 mg/L (As) , 0.44 mg/L (Mn), 0.01 mg/L (Pb), 0.01 mg/L (Cd) and 0.38 mg/L (Zn). Levels of heavy metals (As, Ni, Pb,) were below the WHO guideline values for drinking water while metals such as (Hg, Mn, Fe, Cd) were all above the EPA and WHO recommended safety guideline limit for drinking water. All the metal concentrations in the sediment were higher than that of the water samples in both dry and wet seasons. The concentrations of all the metals studied were below USEPA guideline values. Results of Pollution Indices computed namely, contamination factors (Cf), Geo-Accumulation Index (I-Geo) Pollution load Index showed no pollution for all metals studied except mercury and iron which showed moderate pollution. There was no correlation between the pH and heavy metals in the water samples. However the metal concentrations in the river sediments showed a significant difference with pH. Ions in the water (K+, Na+, SO42-, PO43- and NO3-) showed seasonal variations. Also physic- chemical parameters such as total dissolved solids, total suspended solids, total alkalinity, total hardness, electrical conductivity and temperature showed seasonal variations in their concentration levels. The high levels of metals such as Mn, Fe, Cd and Hg indicates that artisanal gold mining has adverse impact on the Birim River. Keywords: Birim River, water, sediment, heavy metals, seasonal variation, Contamination factors, Geo- Accumulation Index, Pollution load Index

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Gold Mining, Heavy Metals, Seasonal Variation

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