Cyanide Contamination of the Puyango-Tumbes River Caused by Artisanal Gold Mining in Portovelo-Zaruma, Ecuador

Artisanal and small-scale gold mining and biodiversity: a global literature review

Artisanal and small-scale gold mining (ASGM) is crucial to the livelihoods of close to 20 million people in over 80 countries, including 4-5 million women, mainly in rural areas with limited alternative economic prospects, particularly in developing countries. ASGM is largely informal, which can add to the challenge of addressing negative social and environmental effects including impacts on biodiversity. However, with proper guidance, ASGM can operate in a responsible manner, using cleaner production methods that minimize impacts on human health and the environment. This study presents and analyzes the interactions between ASGM and biodiversity based on new findings from 27 ASGM National Action Plans (NAPs) developed within the framework of Article 7 and Annex C of the Minamata Convention on Mercury, as well as a global literature review of more than 100 publications. In terms of key findings according to the literature reviewed, alongside other human occupation such as agriculture and industrial activities, ASGM also has an impact on the environment and biodiversity. The interrelationship between ASGM and biodiversity, including protected areas, is pervasive at every stage of ASGM operations, from extraction to mine closure, and generates significant impacts on the surrounding ecosystems. These impacts include, in descending order of most reported impacts: deforestation, soil degradation, chemical contamination of aquatic and terrestrial systems, and changes to the turbidity of watercourses. Tropical regions and key species such as amphibians and freshwater fish are among the most affected. Singly or combined, these environmental stressors lead to loss or deterioration of habitat and, by extension, indigenous biodiversity and ecosystem services. In addition, legal, institutional, and regulatory frameworks and related measures, inadequate or non-existent in some cases, may not necessarily support sustainable practices, often resulting in exploited sites abandoned without remediation, reclamation, rehabilitation, or restoration measures. To mitigate such impacts a key recommendation arising from the literature review is to strengthen the integration of the interrelationship between ASGM and biodiversity in the implementation of existing relevant national strategies, including those developed under the NAPs. The global literature review also highlights the importance of a multi-stakeholder, systemic approach combining the use of geospatial analysis, scientific and local knowledge, as well as the adaptation of the relevant frameworks, capacity building, and awareness raising. This approach can inform decision making with a view to developing sustainable initiatives that prevent and reduce the impacts of artisanal and small-scale gold mining on ecosystems, and that preserve biodiversity.

Mercury cyanide complexes and their relevance as environmental contaminants

This review addresses the formation and relevance of mercury cyanide complexes as environmental contaminants. Gold extraction is traditionally carried out through the process of mercury amalgamation (Hg) due to its simplicity and low cost. However, this process is inefficient, capturing only about 30% of the gold present in the processed material. Additionally, mercury is toxic, mobile, and capable of accumulating in aquatic ecosystems, leading to its prohibition in several countries. As an alternative, cyanidation has been widely used in gold extraction. However, the frequent combination of Hg amalgamation with cyanidation can result in the formation of mercury cyanide complexes, which can be released into local water bodies, potentially impacting human health and the environment. This article reviews the existing knowledge of these complexes and highlights the remaining gaps in understanding their environmental behavior. It also emphasizes the need to address concerns related to the formation of these complexes and seek solutions to minimize their negative impacts. Furthermore, the article highlights the lack of updates in the literature regarding the impacts of cyanidation and the limited availability of comprehensive information on the topic. It is essential to conduct updated research in this area to advance knowledge and promote safer and more responsible practices in the mining industry.

Human health risk assessment due to mercury use in gold mining areas in the Ecuadorian Andean region

Mining activity drives economic development and has established itself as one of the main industrial spheres globally. However, illegal, and artisanal gold mining, which uses mercury (Hg), is a major source of global pollution. Hg is highly toxic and persistent in the environment, affecting human health and the ecosystem. The objective of this research is to; (a) analyze Hg concentrations in surface waters of nine provinces of the Andean region of Ecuador and compare them with the maximum permissible limits of Ecuadorian regulations, and (b) evaluate the health risk of people exposed to waters with high Hg content through residential and recreational scenarios. In this study, 147 water samples from rivers and streams were analyzed. The results revealed worrying levels of Hg, especially in the provinces of Azuay and Loja where Hg values of up to 0.0913 mg/L and 0.0387 mg/L, respectively, were detected. In addition, it was found that 45% of the samples did not meet the water quality criteria for the preservation of aquatic life, which represents a severe risk to the ecosystem. The probabilistic risk analysis yielded values that exceeded the acceptable exposure limit for adults and children in residential settings in Azuay and Loja, while in the recreational scenario the safe exposure limit was exceeded for both receptors only in the province of Azuay. The elevated presence of Hg in the provinces, mainly in Azuay and Loja, possibly related to illegal gold mining activity, represents a threat to water quality and aquatic life in the Andean region of Ecuador. Children are especially vulnerable, and effective regulation is required to ensure the safety of the population. This study provides valuable information for decision makers regarding the risk associated with Hg exposure in areas of mining activity in the Ecuadorian Andean region. In addition, it can contribute to the development of policies and strategies to control contamination in mining environments and protect human and environmental health in the region.

Human and environmental exposure to rare earth elements in gold mining areas in the northeastern Amazon

Rudimentary methods are used to exploit gold (Au) in several artisanal mines in the Amazon, producing hazardous wastes that may pose risks of contamination by rare earth elements (REEs). The objectives of this study were to quantify the concentrations of REEs and assess their environmental and human health risks in artisanal Au mining areas in the northeastern Amazon. Thus, 25 samples of soils and mining wastes were collected in underground, colluvial, and cyanidation exploration sites, as well as in a natural forest that was considered as a reference area. The concentrations of REEs were quantified using alkaline fusion and inductively coupled plasma mass spectrometry, and the results were used to estimate pollution indices and risks associated with the contaminants. All REEs showed higher concentrations in waste deposition areas than in the reference area, especially Ce, Sc, Nd, La, Pr, Sm, and Eu. Pollution and enrichment levels were higher in the underground and cyanidation mining areas, with very high contamination factors (6.2-27) for Ce, Eu, La, Nd, Pr, Sm, and Sc, and significant to very high enrichment factors (5.5-20) for Ce, La, Nd, Pr, and Sc. The ecological risk indices varied from moderate (167.3) to high (365.7) in the most polluted sites, but risks to human health were low in all areas studied. The results of this study indicate that artisanal Au mining has the potential to cause contamination, enrichment, and ecological risks by REEs in the northeastern Amazon. Mitigation measures should be implemented to protect the environment from the negative impacts of these contaminants.

Mercury Exposure and Its Health Effects in Workers in the Artisanal and Small-Scale Gold Mining (ASGM) Sector—A Systematic Review

Gold is one of the most valuable materials but is frequently extracted under circumstances that are hazardous to artisanal and small-scale gold miners’ health. A common gold extraction method uses liquid mercury, leading to a high exposure in workers. Therefore, a systematic review according to the PRISMA criteria was conducted in order to examine the health effects of occupational mercury exposure. Researching the databases PubMed^®, EMBASE^® and Web of Science^TM yielded in a total of 10,589 results, which were screened by two independent reviewers. We included 19 studies in this review. According to the quantitative assessment, occupational mercury exposure may cause a great variety of signs and symptoms, in particular in the field of neuro-psychological disorders, such as ataxia, tremor or memory problems. However, many reported symptoms were largely unspecific, such as hair loss or pain. Most of the included studies had a low methodological quality with an overall high risk of bias rating. The results demonstrate that occupational mercury exposure seriously affects miners’ health and well-being.

Artisanal gold mining in the eastern Amazon: Environmental and human health risks of mercury from different mining methods

Artisanal gold (Au) mining is the activity with the highest consumption of mercury (Hg) and the main source of environmental contamination by this element, which is a recurring problem in the Amazon. In this study, contamination and risks caused by Hg to the environment and human health were evaluated in different forms of artisanal Au mining in the Brazilian Amazon. For this purpose, 25 samples of soils and tailings were collected in three types of artisanal mine and one native forest. The mineralogical analysis revealed that there is no occurrence of minerals constituted by Hg. However, the concentrations of Hg in underground mining tailings were very high and exceeded the prevention values established by Brazilian environmental legislation, indicating elevated risk to the ecosystem and human health. The enrichment factor indicated that underground mining tailings are enriched by Hg, submitted to cyanidation or not, suggesting anthropogenic source for the high concentrations of Hg. The geoaccumulation index and the contamination factor showed that the colluvial mining tailings are moderately contaminated, and the tailings from underground mining are highly to extremely contaminated, leading to very high risks to the environment and the health of children from the region. These results represent a great contribution to the Amazon, since they provide subsidies for the definition of policies to mitigate environmental contamination and associated risks.

History, Current Situation and Challenges of Gold Mining in Ecuador’s Litoral Region

Gold mining in Ecuador has been present in the country since Inca times; over the years interest in the mineral has increased, leading to the creation of legislation to control the mining sector in a safe manner. The Litoral region consists of seven provinces, six of which have registered gold concessions; the most affected provinces are El Oro and Esmeraldas. The objective of this study was to analyze the historical and current situation of artisanal and industrial gold mining in the Litoral region of Ecuador. Different methodologies were used for the elaboration of this study, including bibliographic review, grey literature, field interviews and a validation of expert judgment. The main results indicate that El Oro and Esmeraldas are essentially the most conflictive areas in the region, as they have sometimes had to establish precautionary measures due to the risks caused by illegal mining. In addition, in both areas there is a great socioeconomic impact ranging from lack of opportunities, forgetfulness, migration, emigration, and violation of rights, among others. With respect to environmental impacts, the study highlights the contamination of water sources (which leads to a lack of drinking water for people), and damage to aquatic and terrestrial ecosystems. Finally, the study concludes that the authorities should control the mining sector more by implementing more laws and carrying out inspections to put an end to illegal gold mining, in order to improve the situation in the areas.

Neurodevelopment and exposure to neurotoxic metal(loid)s in environments polluted by mining, metal scrapping and smelters, and e-waste recycling in low and middle-income countries

This review covers a wide body of literature to gain an understanding of the impacts of informal activities related to metal extraction (primary mining and recycling) on early life exposure to neurotoxicants and on neurodevelopment. In primary mining, gold extraction with Hg amalgamation is the main environmental cause of Hg pollution in most artisanal small-scale gold mining (ASGM) activities around the world. Nevertheless, in Sub-Saharan Africa (SSA), Pb disrupted from gold-related ores, mining, and artisanal cookware production are an important neurotoxicant that seriously contaminates the affected population, with devastating effects on children. In e-waste recycling settings, the range of neurotoxic substances that contaminate mothers and children is wider than in primary mining environments. Thus, Hg and Pb are major pre- and postnatal neurotoxicants affecting children in the informal metal extraction activities and SSA countries show the highest record of human contamination and of neurotoxic effects on children. There are additional sources of neurotoxic contamination from mining and metal processing activities (cyanide tailing in South America and SSA) and/or co-exposure to Hg-containing products such as cosmetics (soaps and Hg-based skin lightning creams in Africa) and pediatric Thimerosal-containing vaccines (TCVs, that breaks down to ethyl-mercury) in current use in middle and low income countries. However, the action of these neurotoxicants (per se or in combination) on children needs more attention and research. Studies show a negative association between biomarkers of all environmental metal(loid)s (As, Cd, Hg, Mn, and Pb) studied and neurodevelopment in young children. Sadly, in many unregulated activities, child labor is widely employed, thus presenting an additional occupational exposure. Children living in polluted environments related to metal processing are disproportionately exposed to a wide range of co-occurring neurotoxic substances. The review showed compelling evidence from highly representative parts of the world (Africa, Asia, and Latin America) that the studied neurotoxic substances negatively affected areas of the brain associated with language, memory and executive function, as well as psychosocial behavior. Protecting the environment and children from unregulated and highly polluting metal extraction and processing are inextricably intertwined and deserve urgent attention.

Artisanal and Small Gold Mining and Petroleum Production as Potential Sources of Heavy Metal Contamination in Ecuador: A Call to Action

Mining and petroleum production are the source of many elements and base materials fundamental for our modern way of life. The flip side of these keystone industries is the environmental degradation they can cause if not properly managed. Metallic mining and petroleum production can contaminate the local ecosystem with sediments, chemicals used in the industrial processes and heavy metals, part of the metallic ore or oil reservoir. The objective of this project was to analyze the spatial distribution of the presence of different potentially hazardous elements that make up the metallic deposits and oil reservoirs in Ecuador, focused mainly on artisanal and small-scale gold mining (ASGM) districts. Additionally, we were interested in analyzing this information under the local political and administrative contexts which are key to determining how likely it is that mismanagement of the local mineral deposits and petroleum exploitation projects will end up causing environmental degradation. An extensive and intensive literature search was conducted for information on the presence and concentration of 19 potentially harmful elements. We analyzed data on 11 metallic deposits throughout Ecuador and a major oilfield in the Ecuadorian Amazon basin. We used geographic information systems to analyze the spatial distribution of these reservoirs and their mineral compositions. The results indicated a widespread distribution and high concentration of elements potentially harmful for human health, such as mercury, cadmium and arsenic, throughout the metallic deposits in Ecuador. This is particularly true for long-exploited ASGM districts, such as Ponce-Enríquez, Portovelo-Zaruma and Nambija. This study highlights the importance of understanding geological diversity and its potential risks to better protect the biological diversity and public health of its inhabitants. Furthermore, we consider our work not as a call to stop ASGM mining nor petroleum production, but on the contrary as a strong call to plan every mining and petroleum production project considering these risks. Moreover, our work is a call to action by the local government and authorities to stop corruption and fulfill their duties overseeing the activities of mining and petroleum companies, stopping illegal mining, helping ASGM communities to improve their environmental standards, finding alternative income sources and protecting the local environment.

Mercury methylation in cyanide influenced river sediments: A comparative study in Southwestern Ghana

Studies on the influence of CN on Hg methylation rates in aquatic systems draining gold mining (artisanal and small-scale) communities in Africa are rare. The study assessed the influence of CN on Hg methylation in aquatic sediments of two major river systems draining artisanal and small-scale gold mining (ASGM) communities of the Prestea-Huni Valley district, Southwestern Ghana. The miners extract gold (Au) through exclusive amalgam [Hg-Au] formation or cyanidation of Au-rich Hg-contaminated tailings, or a combination of both techniques. Hg water solubility and probable mercuric compounds in sediments of Hg-contaminated CN-loaded (River Aprepre) and Hg-contaminated non-CN (River Ankobra) aquatic systems within the district were investigated. THg was determined by CV-AAS after HF/HNO₃/HCl digestion. MeHg in sediments were extracted with H₂SO₄/KBr/CuSO₄-CH₂Cl₂; followed by aqueous-phase propylation, preconcentration-on-Tenax, and GC-CV-AFS. River Aprepre showed 4.58-14.83 ngMeHg/g as Hg (1.4-3.7% THg as MeHg), with 241-415 ngTHg/g, and 0.05-0.21 mgCN/kg. For River Ankobra, MeHg ranged 0.24-1.21 ngMeHg/g (0.08-0.35% THg as MeHg) with 162-490 ngTHg/g dw and CN < 0.001 mg/kg. There was positive correlation (r² = 0.5974; p < 0.01) between MeHg and CN in River Aprepre. The water-soluble fraction of Hg in sediment from both rivers was < 1% of THg. Hg in sediments from River Aprepre were generally more soluble than that from River Ankobra, indicating that Hg in sediments from River Aprepre were potentially more bioavailable for methylation. Accordingly, the presence of CN in Hg-dominated river sediments potentially influences and enhances the solubility and mobility of Hg, resulting in increased Hg methylation rates.

Solid-phase partitioning and release-retention mechanisms of copper, lead, zinc and arsenic in soils impacted by artisanal and small-scale gold mining (ASGM) activities

Artisanal and small-scale gold mining (ASGM) operations are major contributors to the Philippines' annual gold (Au) output (at least 60%). Unfortunately, these ASGM activities lacked adequate tailings management strategies, so contamination of the environment is prevalent. In this study, soil contamination with copper (Cu), lead (Pb), zinc (Zn) and arsenic (As) due to ASGM activities in Nabunturan, Davao de Oro, Philippines was investigated. The results showed that ASGM-impacted soils had Cu, Pb, Zn and As up to 3.6, 83, 73 and 68 times higher than background levels, respectively and were classified as 'extremely' polluted (CD = 30-228; PLI = 5.5-34.8). Minerals typically found in porphyry copper-gold ores like pyrite, chalcopyrite, malachite, galena, sphalerite and goethite were identified by XRD and SEM-EDS analyses. Furthermore, sequential extraction results indicate substantial Cu (up to 90%), Pb (up to 50%), Zn (up to 65%) and As (up to 48%) partitioned with strongly adsorbed, weak acid soluble, reducible and oxidisable fractions, which are considered as 'geochemically mobile' phases in the environment. Although very high Pb and Zn were found in ASGM-impacted soils, they were relatively immobile under oxidising conditions around pH 8.5 because of their retention via adsorption to hydrous ferric oxides (HFOs), montmorillonite and kaolinite. In contrast, Cu and As release from the historic ASGM site samples exceeded the environmental limits for Class A and Class C effluents, which could be attributed to the removal of calcite and dolomite by weathering. The enhanced desorption of As at around pH 8.5 also likely contributed to its release from these soils.

Gravity Concentration in Artisanal Gold Mining

Worldwide there are over 43 million artisanal miners in virtually all developing countries extracting at least 30 different minerals. Gold, due to its increasing value, is the main mineral extracted by at least half of these miners. The large majority use amalgamation either as the final process to extract gold from gravity concentrates or from the whole ore. This latter method has been causing large losses of mercury to the environment and the most relevant world’s mercury pollution. For years, international agencies and researchers have been promoting gravity concentration methods as a way to eventually avoid the use of mercury or to reduce the mass of material to be amalgamated. This article reviews typical gravity concentration methods used by artisanal miners in developing countries, based on numerous field trips of the authors to more than 35 countries where artisanal gold mining is common.