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<p>Ghana’s rapidly degrading land, water and ecosystems are often attributed to small-scale and illegal mining practices, with the large-scale gold mining companies unblemished when environmental degradation and pollution are discussed. However, their operations rely on several support services, such as gold assaying laboratories (GAL), whose impact on the environment has never been evaluated or included in the environmental impact assessment of the large-scale mines. This study took 60 wastewater samples from a GAL to determine the physicochemical qualities and heavy metals (HMs) levels. For the HMs analysis, the samples were digested using a mixture of perchloric, nitric and hydrochloric acid, and analysed using atomic absorption spectroscopy. The contamination factor (CF), ecological risk factor (ERF), potential ecological risk index (PERI), effluent pollution index (EPI) and effluent discharge quality index (EDQI) were calculated to assess the ecological risks posed by untreated wastewater from GAL. The pH was below the lower Ghana Environmental Protection Agency (GEPA) limit of pH 6, whilst the electrical conductivity, phosphorus and cyanide concentrations were above the threshold of GEPA. The levels of heavy metals were Cd (0.69 ± 0.19&#xa0;mg/L), Zn (5.56 ± 2.12&#xa0;mg/L), Fe (13.7 ± 4.01&#xa0;mg/L), Cu (3.40 ± 1.73&#xa0;mg/L), Mn (1.70 ± .031&#xa0;mg/L), Ni (0.33 ± 0.04&#xa0;mg/L), As (2.09 ± 0.04&#xa0;mg/L), Pb (1.22 ± 0.05&#xa0;mg/L) and Hg (0.09 ± 0.04&#xa0;mg/L). The individual HMs (except Zn) posed a very high ecological risk, and collectively they posed a severe risk to aquatic species in the receiving environment. The EPI and the EDQI showed that the wastewater from the GAL exhibited a very high degree of pollution. Correlation analysis showed a moderate inverse correlation between EPI, TDS and TSS. Therefore, wastewater from GAL should be treated to reduce its EC, cyanide and phosphorus concentrations using technologies such as ion exchange columns, biological phosphorus removal systems or reverse osmosis. The GEPA should develop a robust monitoring program to assess the compliance of GAL with its effluent discharge permits. Finally, the environmental impact assessment of large mining companies should consider the inclusion of the footprints of their support service providers.</p>

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The dull side of gold ore exploration and analysis: an assessment of heavy metal pollution and ecological risk posed by untreated wastewater from gold assaying laboratories

  • 期刊论文

  • 发表日期：

    2025年7月4日

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  • Stephen Arthur,
  • Lawson Mensah,
  • Kwabena Nsafoah Koduah,
  • Ethel Bentil,
  • Solomon Nandomah,
  • Isaac Kow Tetteh,
  • Jonathan Nartey Hogarh

摘要

Ghana’s rapidly degrading land, water and ecosystems are often attributed to small-scale and illegal mining practices, with the large-scale gold mining companies unblemished when environmental degradation and pollution are discussed. However, their operations rely on several support services, such as gold assaying laboratories (GAL), whose impact on the environment has never been evaluated or included in the environmental impact assessment of the large-scale mines. This study took 60 wastewater samples from a GAL to determine the physicochemical qualities and heavy metals (HMs) levels. For the HMs analysis, the samples were digested using a mixture of perchloric, nitric and hydrochloric acid, and analysed using atomic absorption spectroscopy. The contamination factor (CF), ecological risk factor (ERF), potential ecological risk index (PERI), effluent pollution index (EPI) and effluent discharge quality index (EDQI) were calculated to assess the ecological risks posed by untreated wastewater from GAL. The pH was below the lower Ghana Environmental Protection Agency (GEPA) limit of pH 6, whilst the electrical conductivity, phosphorus and cyanide concentrations were above the threshold of GEPA. The levels of heavy metals were Cd (0.69 ± 0.19 mg/L), Zn (5.56 ± 2.12 mg/L), Fe (13.7 ± 4.01 mg/L), Cu (3.40 ± 1.73 mg/L), Mn (1.70 ± .031 mg/L), Ni (0.33 ± 0.04 mg/L), As (2.09 ± 0.04 mg/L), Pb (1.22 ± 0.05 mg/L) and Hg (0.09 ± 0.04 mg/L). The individual HMs (except Zn) posed a very high ecological risk, and collectively they posed a severe risk to aquatic species in the receiving environment. The EPI and the EDQI showed that the wastewater from the GAL exhibited a very high degree of pollution. Correlation analysis showed a moderate inverse correlation between EPI, TDS and TSS. Therefore, wastewater from GAL should be treated to reduce its EC, cyanide and phosphorus concentrations using technologies such as ion exchange columns, biological phosphorus removal systems or reverse osmosis. The GEPA should develop a robust monitoring program to assess the compliance of GAL with its effluent discharge permits. Finally, the environmental impact assessment of large mining companies should consider the inclusion of the footprints of their support service providers.