Contamination impact and human health risk assessment of heavy metals in surface soils from selected major mining areas in Ghana.

Analysis of soil samples around pristine and major gold-mining areas in Ghana was carried out for heavy metals as part of a larger soil contamination and metal background study. The surface soil samples were digested using microwave digester (aqua regia) and analyzed with ICP-MS for As, Cd, Hg, Zn, Co, Cu, Mn, Fe, Al, V, Cr, and Pb. The average concentrations (mg/L) for the metals ranged from 0.01 ± 0.01 (Cd) to 86,859.36 ± 47.07 (Fe) for the pristine sites, and 0.01 ± 0.01 (Cd) to 59,006.95 ± 79.06 (Fe) for the mining sites. Mercury was below the detection limit of the analytical instrument (0.029). The concentrations of heavy metals from this study were used to assess their contamination levels, and health risks. The results showed that, the metals ranked by severity of health risks as As > Pb > Cr > Cd. Principal component analysis (PCA) and cluster analysis showed two groupings with the PCA showing metals variability explained by 79.02%. Results from the PCA and Cluster analysis indicate anthropogenic sources of the metals which may be emanating from gold-mining activities. Results from multi-criteria ranking and pattern recognition employing PROMETHEE and GAIA revealed major contribution of the metals from the mining sites with metal variability explained by 72.83%. This is the first time a multi-criteria approach is employed to characterize heavy metal contamination in Ghana, and the study nevertheless brought to light the impact of mining on human health and the environment with implications for other mineral areas around the globe.

Assessment of contamination and health risk of heavy metals in selected water bodies around gold mining areas in Ghana.

Heavy metal contamination of selected rivers in Ghana was studied as part of a bigger project aimed at setting background standard for heavy metals in the Ghanaian environment. Water samples were collected from major mining and eight pristine areas. The samples were acid digested with aqua-regia and analyzed with ICP-MS for As, Cd, Hg, Zn, Cu, Mn, Fe, Cr, Al, V, Co, Ni, and Pb. The average concentrations (mg/L) from the pristine sites ranged from 0.002 ± 0.00(As) to 0.929 ± 0.06 (Fe) and 0.002 ± 0.00 (Pb) to 20.355 ± 5.60 (Fe) from the mining sites. With the exception of Al, Fe, and Mn, the metals level were found to be within the WHO and USEPA guideline limits. Hazard quotients (HQ) for ingestion and dermal contact for pristine and mining samples ranged from 3.00E-04 (Cu) to 0.84 (Cr) and 2.40E-06 (Cu) to 7.44 (As), respectively. The carcinogenic risk (CR) for ingestion and dermal contact ranged from 5.03E-06 to 1.71E-07 (Cr) and 4.22E-08 to 1.44E-09 (Cr), respectively. Arsenic showed a CR value higher than the acceptable limit (1.8E-02) from the mining sites which poses carcinogenic health threat. Multicriteria ranking suggests Birim river (EAM) as the most contaminated. The pattern recognition and multicriteria approach in characterizing the heavy metal contamination (for the first time in the case of Ghana) from the various sites will provide fresh insights into the risk assessment of heavy metals in contaminated surface waters.

Distribution and Risk Assessment of Heavy Metals in Surface Water from Pristine Environments and Major Mining Areas in Ghana.

BACKGROUND: Ghana, like many countries in Africa, has a history of heavy metal pollution largely emanating from industrial effluent discharges and anthropogenic deposits on prevailing winds of pollutants from industrial activities. One of the biggest contributors to pollution in the Ghanaian environment is mineral mining. OBJECTIVES: The aim of this study was to determine the distribution and health risks of heavy metals in surface water from both pristine environments and major mining areas in Ghana. METHODS: A total of 32 composite samples were collected between September and October, 2014 to assess concentrations of heavy metals and pollution levels, as well as cancer and non-cancer risks to human health from exposure to heavy metals from four major mining regions and four rain forest reserves in the Western, Ashanti, Brong Ahafo and Eastern regions of Ghana. Samples were analyzed using atomic absorption spectrometry. RESULTS: The mean concentrations (mg/L) of heavy metals at the pristine sites ranged from 1.747 for iron (Fe) to 0.001 for mercury (Hg) and 0.453 for Fe to 0.002 for Hg at the mining sites. All the metals were found to be below World Health Organization (WHO) and United States Environmental Protection Agency (USEPA) recommended limits except for Hg, which was at the USEPA guideline limit. However, the concentrations of the metals from the mining sites were found to be slightly higher than those from the pristine sites. CONCLUSIONS: The concentrations of heavy metals in the Nyam, Subri, Bonsa and Birim Rivers from the mining sites and the Atiwa Range, Oda, Ankasa and Bosomkese Rivers from the pristine sites were found to be either below or within the USEPA and WHO's recommended limits for surface water. The health risk assessment values for the hazard quotient for ingestion of water (HQing), dermal contact (HQderm) and chronic daily intake (CDI) indicated no adverse effects as a result of ingestion or dermal contact from the rivers. However, arsenic (As) in both the pristine and mining sites and chromium (Cr) in the pristine sites pose a carcinogenic threat to the local residents.