Integrated Assessment of Artisanal and Small-Scale Gold Mining in Ghana—Part 2: Natural Sciences Review

Abstract

This paper is one of three synthesis documents produced via an integrated assessment (IA) that aims to increase understanding of artisanal and small-scale gold mining (ASGM) in Ghana. Given the complexities surrounding ASGM, an integrated assessment (IA) framework was utilized to analyze socio-economic, health, and environmental data, and co-develop evidence-based responses with stakeholders. This paper focuses on the causes, status, trends, and consequences of ecological issues related to ASGM activity in Ghana. It reviews dozens of studies and thousands of samples to document evidence of heavy metals contamination in ecological media across Ghana. Soil and water mercury concentrations were generally lower than guideline values, but sediment mercury concentrations surpassed guideline values in 64% of samples. Arsenic, cadmium, and lead exceeded guideline values in 67%, 17%, and 24% of water samples, respectively. Other water quality parameters near ASGM sites show impairment, with some samples exceeding guidelines for acidity, turbidity, and nitrates. Additional ASGM-related stressors on environmental quality and ecosystem services include deforestation, land degradation, biodiversity loss, legacy contamination, and potential linkages to climate change. Though more research is needed to further elucidate the long-term impacts of ASGM on the environment, the plausible consequences of ecological damages should guide policies and actions to address the unique challenges posed by ASGM.

Senegalese artisanal gold mining leads to elevated total mercury and methylmercury concentrations in soils, sediments, and rivers

“…Note that drinking water and well water THg concentrations were greater than THg concentrations in half of the river water samples; though the concentration of THg was below the WHO drinking water guideline, if ASGM activities intensify in these communities and utilize increased amounts of Hg, the concentrations of THg in water could approach the WHO drinking water guideline. Maximum water THg concentrations at Senegalese ASGM sites were the second highest reported for other ASGM sites in Africa [Adjei- Kyereme et al, 2015] with the range and median values comparable to those reported in the literature (Table 1) [e.g., Gray, 2002b;Taylor et al, 2005;Donkor et al, 2006;Feng et al, 2006;Rajaee et al, 2015]. Maximum water MeHg concentrations at Senegalese ASGM sites were exceeded in only one study [Feng et al, 2006].…”

“…Differences in edaphic, aeolian, and climatic conditions in West Africa compared to other locations can influence patterns and pathways of atmospheric Hg deposition, runoff and fluvial transport of Hg compounds, and conditions for the conversion of inorganic Hg to MeHg -the more bioaccumulative form. While the few studies of ASGM in Africa (mostly eastern Africa) have affirmed that Hg concentrations are high near mining sites [e.g., Taylor et al, 2005;Rajaee et al, 2015], research is critically needed that better characterizes the spatial extent and magnitude of Hg contamination.…”

“…While many studies have investigated Hg use in tropical regions such as the Amazon, particularly in relation to the naturally Hg-rich soils [e.g., Cordy et al, 2011;Terán-Mita et al, 2013;Balzino et al, 2015], little quantitative work has been conducted in an environment with the climatic, edaphic, and geologic conditions of West Africa where crude technology and approaches are utilized to extract the gold [but see Taylor et al, 2005a;Niane et al, 2014;Rajaee et al, 2015]. Despite the prevalence of gold mining in Senegal, to our knowledge only one study has quantified Hg from ASGM in Senegal in environmental media [Niane et al, 2014].…”

Emergy Perspectives on the Environmental Performance and Sustainability of Small-Scale Gold Production Systems in Ghana

“…The study sites and case systems were selected based on several considerations emanating from the research problem. For instance, the selected cases are located both on-and off-river and are facing environmental problems [5,[13][14][15]. In terms of the quantity and production capacity, the selected cases are the most common type of ASGM practiced locally.…”

“…Hilson [12] observed that the mining has been responsible for and has intensified the removal of vast quantities of surface vegetation, including protected forestland, mainly because small-scale gold mining is a migratory industry. Several studies have recognized that ecosystem stressors, such as deforestation, forest degradation, biodiversity loss, riparian ecosystem deterioration, soil quality decline, etc., are evident in regions where ASGM activities are on-going [4,5,[13][14][15]. Ultimately, mining overwhelms the inherent abilities of the affected ecosystems to be restored to their previous states without assistance.…”