Jennifer J. Hinton

Clean artisanal gold mining: a utopian approach?

Artisanal and small-scale mining (ASM) provides an important source of livelihood for rural communities throughout the world. These activities are frequently accompanied by extensive environmental degradation and deplorable socio-economic conditions, both during operations and well after mining activities have ceased. As gold is easily sold and not influenced by the instability of local governments, it is the main mineral extracted by artisanal miners. Mercury (Hg) amalgamation is the preferred gold recovery method employed by artisanal gold miners and its misuse can result in serious health hazards for miners involved in gold extraction, as well as for surrounding community inhabitants, who may be exposed to mercury via the food chain. The rudimentary techniques characteristic of ASM result in a number of occupational hazards, other although most risks are primarily attributed to machinery accidents and ground failure, such as landslides and shaft collapses. Several technologies and methods commonly utilized by large-scale mining operations can be downsized to smaller scale operations. However, the likelihood that miners will adopt these large-scale methods, or those developed specifically for ASM, depends upon some key factors. For an artisanal miner, these factors include: (1) increased or comparable simplicity, (2) quick recovery of the economic mineral, and (3) demonstrated financial gain. Other practical aspects, such as the availability of materials (chemicals, steel rods, piping, generators, etc), capital and operating cost requirements and access to technical support, also influence acceptance of new techniques. This article will review four inter-related areas: first, the limitations and benefits, for ASM, of a number of specific technologies; second, the role of Processing Centers in education, information dissemination and provision of “clean” services; third, benefits and challenges associated with formalization of ASM activities; and fourth, the contribution of ASM to the development of sustainability of communities, primarily through diversification of livelihoods. The appropriate application of technologies, particularly given the diversity of ASM communities around the world, will also be explored.  2002 Elsevier Science Ltd. All rights reserved.

Abandoned artisanal gold mines in the Brazilian Amazon: A legacy of mercury pollution

The modern gold rush in the Brazilian Amazon attracted millions of people to become artisanal miners in order to escape complete social marginalization. The rudimentary nature of artisanal mining activities often generates a legacy of extensive environmental degradation, both during operations and well after mining activities have ceased. One of the most significant environmental impacts is derived from the use of mercury (Hg), which is illegal for use in gold amalgamation in Brazil, but continues to be the preferred method employed by artisanal gold miners. The general population is unaware of the capricious nature of mercury and artisanal mining activities. Moreover, individuals in positions of political or economic influence tend to be negatively biased towards artisanal mining and government policies do not effectively address the realities of these activities. Affected communities have consequently been ignored, and mistrust towards outside parties is high. Not surprisingly, miners are suspicious of and unlikely to employ externally derived solutions to reduce mercury emissions. This article reviews the use of mercury in artisanal mining and highlights the role miners, governments and non-governmental organizations (NGOs) have played in communicating facts, perpetuating myths and deriving solutions for mercury pollution. This article also raises some key concerns that must be addressed to understand the behaviour of mercury in the environment and identifies solutions for problems facing communities where artisanal gold mining operations have been abandoned.

Earthworms as bioindicators of mercury pollution from mining and other industrial activities

Mercury (Hg) can be released into the environment by various natural and industrial processes. Given the potential for environmental discharges from a number of sources and the severity of hazards associated with this highly toxic metal, potential mercury transformations must be well understood to effectively predict and prevent harmful human and environmental health effects. Bioindicators play an important role in identifying the factors controlling Hg toxicity and bioavailability and can ultimately be used to evaluate hazardous situations. A methodology using the earthworm Eisenia foetida has been developed to assess Hg bioavailability in mine tailings and aqueous solutions. Results indicate that E. foetida accumulate Hg and a positive correlation exists between Hg concentrations in worm tissues, the substrate they consume and length of exposure. To investigate the effect of natural organic acids on Hg bioavailability, metallic Hg (Hg0) was dissolved in tannic acid and ‘fed’ to the worms in a substrate of paper and silica sand. Total Hg and methylmercury (MeHg) were analysed to determine whether methylation of Hg was occurring in the substrate, directly within worm intestines, or in the tannic acid–Hg solution. The MeHg:total Hg ratio was up to 160 times higher in worm tissues than both the tannic acid–Hg solution and the substrate. This result is particularly significant in organic-rich systems, where naturally occurring organic acids may be facilitating methylation within organisms digestive tracts.

Using earthworms to assess Hg distribution and bioavailability in gold mining soils.

Between 1980 and 2000, the municipality of Cachoeira do Piriá, located in Pará State, Brazil, experienced an intense gold rush with approximately 5,000 artisanal miners discharging more than four tonnes of mercury into soils, air and aquatic systems. Mercury is dispersed across an area of approximately 2,100 ha and concentrations in soils and sediments frequently exceed 1,000 μg.kg−1. The metallic mercury discharged by miners into the environment has the potential to be transformed into a highly toxic form of mercury, methylmercury. A 28-day bioassay with the earthworm Eisenia fetida was used to assess mercury bioavailability in mine tailings, soils, and sediments. Experiments indicated that the highest Hg concentration in earthworms was associated with low-Hg-organic-rich soils collected from densely vegetated areas despite higher mercury concentrations in organic-poor tailings. This indicates that reaction with organic acids is an important pathway for mercury incorporation into food chains. The quick, inexpensive, and simple bioassay also provided a means to evaluate remedial measures (i.e. by capping “hotspots” with local soils). Earthworm experiments indicate that covering “environmental hotspots” (sites with high Hg bioavailability) with local clay-rich sediments is very effective in terms of preventing uptake of mercury from tailings, while organic-rich sediments are relatively ineffective.

The Influence of Organic Acids on Mercury Bioavailability: Insight from an Earthworm Assessment Protocol

Between 10 and 15 million artisanal and small-scale miners in more than 50 countries directly rely on gold mining for their livelihoods. Mainly due to the rudimentary techniques that characterize artisanal mining, these activities are frequently accompanied by extensive environmental degradation and deplorable socio-economic conditions. Mercury, cheap, easy-to-use and effective, is commonly used to recover gold through amalgamation. Due to its misuse, between 800 and 1000 tonnes of mercury are released into the air, water, and soils by artisanal gold miners every year. This generates serious health hazards for miners involved in gold extraction, as well as for surrounding community inhabitants, who may be exposed via high levels of mercury in fish they consume. The metallic mercury discharged by miners into the environment has the potential to undergo many changes, including the transformation to a readily bioavailable and highly toxic form of mercury, methylmercury. A laboratory methodology using the ear...