International guidelines on mercury management in small-scale gold mining

This article reports on a stakeholder engagement process to develop the International Guidelines on Mercury Management in Small-Scale Gold Mining. Commissioned by the United Nations Global Mercury Project, the purpose of the guidelines is to assist policymakers, practitioners, researchers, miners and the public in developing strategies for reducing mercury use, eliminating major pollution point sources and reducing risks. The guidelines are proposed with the view of supporting miners and their communities by promoting safer, more efficient practices that improve environmental and human health. The paper discusses challenges in addressing mercury issues and technical measures in the guidelines. The paper also highlights the need for interactive engagement in communities to discuss and adapt the guidelines as appropriate, in order to create technology transfer strategies, regulatory measures and strategic priorities that are suitable to the local context.     

A matter of approach: the retort's potential to reduce mercury consumption within small-scale gold mining settlements in Tanzania

The mercury-based gold extraction processes prevalent within small-scale mining are both efficient and harmful. While ensuring relatively high levels of gold recovery, they cause environmental and health problems for people living within mining settlements. This mercury consumption can be minimized by using a simple mercury recycling device known as a retort. While mining legislation in Tanzania dictates the use of retorts for gold recovery, virtually no miners use them, indicating the inadequacy of previous introduction attempts. During action research, retorts were introduced in two mining settlements through a thorough and participatory approach. Twenty miners were given retorts and their attitudes and receptiveness to them were studied. Of the recipients, 18 used the retorts over a period of five months, recycling 10 kilos of mercury. Less mercury was spilled into the environment and miners saved money normally spent on purchasing mercury. The findings have implications for the strategies of development interventions targeting mercury-instigated problems within small-scale gold mining.     

Mercury consumption and contamination of environment in gold mining in China

1　ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｇｏｌｄｉｎｄｕｓｔｒｙｉｎＣｈｉｎａｇｒｏｗｓｕｐｑｕｉｃｋｌｙｗｉｔｈｔｈｅｇｒｏｗｔｈｒａｔｅｏｆａｂｏｕｔ 10 %ｓｉｎｃｅ 90’ｓ.Ｉｎ 1995,ｔｈｅｐｒｏｄｕｃｔｉｏｎｏｆｇｏｌｄｗａｓｏｖｅｒ10 0ｔｏｎｓ/ａ,ａｎｄｉｎ 1996ｒｅａｃｈｅｄ 12 0ｔｏｎｓ/ａ .Ｉｔｉｓｒａｎｋｅｄｓｉｘｔｈｉｎｔｈｅｗｏｒｌｄ(Ｃｈａｎｇ ,1995) .Ｔｈｅｉｒｍａｉｎｐｒｏｃｅｄｕｒｅｓｏｆｇｏｌｄｅｘｔｒａｃｔｉｏｎａｒｅ :(1)ｃｙａｎｉｚａｔｉｏｎｉｎｔｏｔａｌｏｒｅ ｃａｒｂｏ…     

Reducing mercury pollution from artisanal gold mining in Munhena,Mozambique

Artisanal small-scale mining (ASM) is responsible for over 90% of gold production in Mozambique. In 2005, a 15-day pilot training project was held in the village of Munhena, a gold mining community. This intervention aimed at raising awareness related to the environmental and health impacts of mercury amalgamation and introduced alternative practices to reduce mercury release and exposure. In 2007, a 9-day evaluation of the pilot campaign was accomplished and knowledge in regards to mining methods, and the ASM government–community operating relations in Munhena were updated. Miners in Munhena are organized in an association of over 3000 members, work on a 25 year Government granted 143 ha concession and generate a substantial income (producing over 5 kg of gold per month). There remain, however, serious barriers towards sustainable community development. ASM associated environmental and health costs are high, as mercury continues to be used and lost to the environment, and cyanide will be introduced soon. The Government of Mozambique has laid the foundation for supporting this sector; however, resources are limited, and thus restrict ability to fully address these issues. Importantly, malaria and HIV/AIDS are not diagnosed and/or treated effectively within the community, and basic necessities are absent. This paper concludes with recommendations focused on enhancing the ASM sector in Mozambique, and overcoming barriers to sustainability in the community of Munhena.     

Epidemiological investigation on mercury contamination in gold mining and its effect on health

Ｉｎｒｅｃｅｎｔｙｅａｒｓ,ｍｅｒｃｕｒｙｃｏｎｔａｍｉｎａｔｉｏｎｈａｓｂｅｅｎ ｐａｉｄ ｇｒｅａｔａｔｔｅｎｔｉｏｎｔｏｏｖｅｒｔｈｅｗｏｒｌｄ(Ｚｉｌｌｏｕｘ ,1993;Ｍｏｎａｍｙ ,1993;Ｇｕａｎ ,1994;Ｙａｎｇ ,1992 ;Ｌｉ,1993;1994;ＳＣＯＰＥ ,1994) .ＴｈｅｐｒｉｎｃｉｐａｌｆｏｃｕｓｉｓｔｏｄｅｃｒｅａｓｅＨｇｃｏｎｔａｍｉｎａｔｉｏｎｉｎｏｒｄｅｒｔｏｐｒｏｔｅｃｔｔｈｅｅｃｏｓｙｓｔｅｍｅｎｖｉｒｏｎｍｅｎｔａｎｄｔｈｅｈｕｍａｎ’ｓｈｅａｌｔｈ .Ｉｔｉｓｄｉｆｆｅｒｅｎｔｆｒｏｍ“ｍｉ…     

Improving the environmental management of small-scale gold mining in Ghana: a case study of Dumasi

In April 2000, a UNIDO study was carried out in Dumasi, Ghana, the purpose of which was to determine the environmental impacts of mercury prior to the introduction of (mercury) retorts. The sampling program was intended to identify mercury transfers to rivers, soil systems and groundwater. Results show a diffuse contamination of all environmental media in the village. Although there is no evidence of groundwater contamination, sediments are significantly contaminated, and most fish fillets have mercury contents exceeding the United States Food and Drug Agency (US-FDA) action level, and are therefore unfit for human consumption. Mercury losses mainly occur during amalgamation, and have resulted in widespread pollution of soils and sediments throughout the village. Transparent retorts have been introduced and environmental training is ongoing but these efforts have only partially addressed the mercury problem in Dumasi.     

Cyanidation of mercury-rich tailings in artisanal and small-scale gold mining: identifying strategies to manage environmental risks in Southern Ecuador

In many countries, such as Brazil, Colombia, Ecuador, Indonesia, Venezuela and Zimbabwe, amalgamated tailings are leached with cyanide to recover remaining gold. This paper describes a recently completed study conducted at seven gold processing centers in Portovelo-Zaruma, Southern Ecuador, which involved consultation with local miners. The objective of the study was to understand the behaviour of mercury (with a focus on mercury loss) in artisanal gold mining operations through the evaluation of two cyanidation processes (Merrill-Crowe and Carbon-in-pulp), using a participatory approach. In order to assess the kinetics of mercury dissolution in cyanide, a bottle roll test was conducted in the laboratory. In the Merrill-Crowe cyanidation process, an average of 24.2% of metallic mercury was determined to be trapped at the bottom of the agitation tanks; 33.1% of mercury is lost in association with solid material and 11.7% is lost in solution. Approximately 31.0% of mercury in solution is sent to the zinc precipitation cells from which 27.8% is precipitated on the zinc shavings, with 3.23% remaining in solution. The mercury precipitated on to the zinc is lost to the atmosphere when the shavings are burned at 900 °C. In the Carbon-in-pulp (CIP) leaching system, 11.2% of the mercury is lost with the solid tailings; 31.6% of the mercury is associated with fine particles in suspension and 50.8% is likely dissolved. About 2.68% is trapped at the bottom of the tank and 3.72% is absorbed by the activated carbon. The bottle roll test revealed that mercury dissolution is directly proportional to cyanide concentration. At 10 g/ton of cyanide, approximately 42% of mercury was leached, whereas all gold was solubilized. During this study, miners recognized the risk associated with the cyanidation of mercury-rich tailings, and were aware of how much mercury is discharged to local streams and to the atmosphere. The active participation of miners in this study has led to the strengthening of their knowledge and awareness of mercury contamination, and has enhanced their understanding of the nature of the problem, as well as the weaknesses and strengths of the system they operate.     

The role of artisanal and small-scale mining in China's economy

The last decades have seen increased international attention paid to a number of features of artisanal and small-scale mining (ASM). The beneficial roles of ASM in society and the economy in many countries, however, are often overlooked, while its negative impacts dominate official press coverage and scholarly publications of the sector. Through a review of the available literature and statistics, this paper works toward building a balanced picture of the overall role of ASM in China. First, the positive and negative impacts of ASM internationally are reviewed, followed by a short review of suggested and actual international policy responses. Then an examination of the impacts and role of ASM in China is undertaken. The authors argue that the contributions of ASM outweigh its negative impacts, but the central government needs to make more effort to regulate, guide and encourage the development of ASM and to create a sound environment for its operations.     

Mercury balance in amalgamation in artisanal and small-scale gold mining: identifying strategies for reducing environmental pollution in Portovelo-Zaruma,Ecuador

The gold ore mined by artisanal and small-scale miners in Portovelo-Zaruma, Ecuador, is processed in custom mills. Miners can choose between Chilean-mill processing centers, where the ore is ground, concentrated and amalgamated, or “Chancha” Centers, where the whole ore is amalgamated. By weighing mercury before and after all unit operations involved in the amalgamation process, it was possible to determine mercury losses. Analyses in eight centers indicated that 51–59% of mercury introduced into the amalgamation process is recovered when miners squeeze the excess mercury. Around 29% of total mercury is lost when miners burn amalgam and gold is melted, and 15% is lost with the tailings. When only gravity concentrates are amalgamated, 1.4% of mercury entering the process is lost with tailings, whereas 29.5% is lost when the whole ore is amalgamated. Approximately 1.5 tonnes/annum of mercury is released in Portovelo-Zaruma, from which 70% is evaporated and 30% is released with tailings. Mercury-contaminated tailings are leached with cyanide in agitated tanks. A large majority of the processing centers dispose the final tailings with mercury and cyanide into the Calera River and Amarillo River. Mercury dissolved with cyanide likely becomes more bioavailable than metallic mercury. A campaign for reducing mercury emissions must focus on the use of individual retorts – mercury pollution control devices – and the elimination of whole ore amalgamation.     

Promoting cleaner production in the Indian small-scale mining industry

India is among the top ten mineral producing nations in the world and its economy depends on the value of minerals produced. Although mineral production has increased significantly since the country’s independence, what continues to be overlooked in is the contribution of resident small-scale mines to national mineral output. Approximately 90% of India’s mines are operating on a small-scale, employing some 0.5 million people. However, because of their rudimentary and highly migratory nature, these operations feature poor environmental management practices and safety conditions. This paper examines the unique techno-economic and socio-cultural characteristics of selected small-scale mining regions in India. It furthermore underscores the need for cleaner production in these regions, and outlines a series of legislative measures pertinent to the industry. The paper concludes by identifying educational- and training-related initiatives, which, if undertaken, could facilitate additional environmental improvement at sites.     

Environmental management in the Brazilian non-metallic small-scale mining sector

Non-metallic mineral resources, albeit very important to meet the needs of the Brazilian population and for exportation, are ill-favored by governments and ignored by the public. Most of this mining is performed by small-scale companies and informal operations that cause extensive and widespread environmental damages. In addition to examining the current state of the industry and its environmental impacts, this paper outlines a series of initiatives for improving (environmental) performance. The suggestions made include improved coordination among public entities responsible for the control of the mining sector; the undertaking of environmental management and reclamation initiatives; research and diffusion of mining and environmental technology; the development and implementation of appropriate licensing procedures for small-scale mines; and the reviewing of environmental impact evaluation and enforcement procedures, and improved regional planning. It is concluded, however, that the proposals will only become a reality if the necessary political actions are taken, and are supported by adequate financing and technical assistance.     

Sustainability and gold mining in the developing world

Generally, the gold mining industry has a negative image because it is potentially highly polluting, its costs often externalized on local communities that host its operations. Recently, there has been growing activism in most countries where rich gold deposits exist. Although the industry has many drawbacks, it can potentially confer many benefits, especially for the people of the developing world, by providing employment and foreign exchange. In the context of the mining sustainable development debate, this paper examines the environmental performance of the gold mining industry in developing countries, and its impacts on resident populations and communities.     

Potential application of mediation to land use conflicts in small-scale mining

Small-scale or artisanal mining is a poverty-driven activity found mainly in remote areas of developing nations. It routinely generates land use conflicts with other stakeholders, primarily large mining companies. The scale of these disputes (occasionally involving armed conflict) is usually sufficient to have significant adverse impacts on the natural environment and the local population. After describing the small-scale mining sector, this paper outlines the characteristics, causes and costs of the land use conflicts with which this activity is often associated. It then discusses some of the more common initiatives that have been taken, primarily by mining companies, to attempt to manage these disputes. Since these approaches are incapable of fully reconciling the range of stakeholder’s interests involved in these conflicts, mediation is proposed as an effective mechanism to achieve their resolution. After an overview of mediation and its potential advantages, the need to apply this process to these disputes is established. Despite its advantages and considerable potential in this application, mediation is not a panacea for resolving all land use conflicts. Based on an extensive literature review, a set of 19 characteristics of disputes that may increase their amenability to mediation is compiled. By then demonstrating that small-scale mining disputes satisfy most of these criteria, the paper concludes that mediation has sufficient promise in this setting to warrant its experimental use.     

Indian small-scale mining with special emphasis on environmental management

Although small-scale mining provides a wealth of socioeconomic benefits to the rural inhabitants of developing countries, there is often total disregard for the environment industry-wide. This paper focuses upon some of the key environmental issues in the Indian small-scale mining industry. The geo-environmental factors constraining the mining of the Himalayan limestone, magnetite, phosphate, and polymetallic sulphur ore deposits are discussed, and the environmental impacts of small-scale operations working prospective deposits are detailed. The paper further examines the schematics of the Environmental Management Plan (EMP) adopted for small-scale mines in India. It is concluded, however, that widespread environmental improvement can only be achieved industry-wide if additional mining cooperatives are formed, and the Indian Government, through their Department of Environment, oversees the implementation of effective mitigation practices for small scale-mines, particularly at the university level.     

Strategies for reducing the environmental impact of reprocessing mercury-contaminated tailings in the artisanal and small-scale gold mining sector: insights from Tapajos River Basin,Brazil

Worldwide, the environmental impacts of artisanal and small-scale gold mining (ASGM) are extensive. Annual losses from mercury, which is used to amalgamate gold, are in the range of 1000 tonnes, and at advanced sites, there is the additional threat of cyanide contamination.Recent developments in The Brazilian Amazon, an area populated by 200,000 small-scale gold miners, have the potential to reduce these impacts considerably. In the locality of Garimpo Ouro Roxo, miners are presently using amalgamation and cyanidation in vat-leaching. Each cycle typically recovers 50% of the gold and lasts 20 days (per tank), consuming around 3300 kg NaCN/month. A new process has been developed and implemented in a pilot plant in this area, involving gravity concentration followed by cyanidation in a ball mill. Concentrate leaching is conducted with a PVC capsule filled with activated carbon inserted in the cyanide solution in the mill. The cycle takes less than 24 h and recovers up to 98% of the gold in the concentrate. The main advantages of wide adoption of this method, apart from a reduced gold recovery cycle and improved recovery, include possible phase out of amalgamation altogether, and marked reductions in cyanide consumption (from current 22,000 kg–980 kg annually).     

Distribution of mercury and methylmercury in river water and sediment of typical manganese mining area

Manganese (Mn) ores contain substantial concentrations of mercury (Hg), and mining and smelting of Mn ores can bring Hg into the surrounding aquatic environment through atmospheric deposition, leaching of electrolytic Mn residue and Mn gangue dump. However, limited is known that how these processes influence the environmental behaviors of Hg in waterbody. Therefore, the seasonal distribution and existing form of Hg in water and sediment in one Mn ore area in Xiushan County, Chongqing were investigated. Our results showed that the mean Hg and methylmercury (MeHg) concentrations in water (n=35) were 5.8 ± 4.6 ng/L and 0.22 ± 0.14 ng/L, respectively. The mean Hg concentrations in retained riverbed and fluvial bank sediment (n=35) were 0.74 ± 0.26 mg/kg and 0.63 ± 0.27 mg/kg, respectively (the mean MeHg concentrations were 0.64 ± 0.40 µg/kg and 0.51 ± 0.30 µg/kg, respectively). It indicated that the mining and smelting of Mn ores were the main sources of anthropogenic Hg, and Mn may inhibit Hg methylation in rivers in Mn ore areas. Mercury in the bound to iron/ Mn (Fe/Mn) oxides of low crystallinity fraction (Hg-OX) accounted for 4.01% and 5.25% of the total Hg concentrations in the retained riverbed and fluvial bank sediment, respectively. The amount of Hg bound to Fe/Mn oxides in sediment increased significantly due to the manganese mining activities in the investigated area. Therefore, it could be hypothesized that high Hg concentrations in river sediment in Mn mining areas are closely related to high Mn concentration in sediment.     

Transport and fate of mercury under different hydrologic regimes in polluted stream in mining area

Seepage from Hg mine wastes and calcines contains high concentrations of mercury (Hg). Hg pollution is a major environmental problem in areas with abandoned mercury mines and retorting units. This study evaluates factors, especially the hydrological and sedimentary variables, governing temporal and spatial variation in levels and state of mercury in streams impacted by Hg contaminated runo . Samples were taken during di erent flow regimes in theWanshan Hg mining area in Guizhou Province, China. In its headwaters the sampled streams/rivers pass by several mine wastes and calcines with high concentration of Hg. Seepage causes serious Hg contamination to the downstream area. Concentrations of Hg in water samples showed significant seasonal variations. Periods of higher flow showed high concentrations of total Hg (THg) in water due to more particles being re-suspended and transported. The concentrations of major anions (e.g., Cl??, F??, NO3?? and SO4 2??) were lower during higher flow due to dilution. Due to both sedimentation of particles and dilution from tributaries the concentration of THg decreased from 2100 ng/L to background levels (< 50 ng/L) within 10 km distance downstream. Sedimentation is the main reason for the fast decrease of the concentration, it accounts for 69% and 60% for higher flow and lower flow regimes respectively in the upper part of the stream. Speciation calculation of the dissolved Hg fraction (DHg) (using Visual MINTEQ) showed that Hg(OH)2 associated with dissolved organic matter is the main form of Hg in dissolved phase in surface waters in Wanshan (over 95%).     

A simplified matrix of environmental impacts to support an intervention program in a small-scale mining site

This paper describes a tool developed to evaluate environmental risks at a Brazilian artisanal small-scale gold mining site. The tool consists of a matrix used to determine the relevance of such risks through the classification of mining activities according to the likelihood that they may cause environmental impacts. The language and method are very simple, and thus appropriate for local stakeholders. It ensures their participation when developing a plan of action for intervention and training. When applied to a pilot site in the Brazilian Amazon, the matrix revealed the variables that pose higher environmental risks. These activities were subsequently addressed in a training program to promote better practices. As a result, the mining activities were improved by 28.8% when comparing compliance to environmental requisites before and after the training program. Specifically, the training program resulted in improved gold recovery, and reduced environmental and health impacts.