Artisanal Small-scale Gold Mining Sites Research Articles

Mercury bioaccumulation in bats in Madre de Dios, Peru: implications for Hg bioindicators for tropical ecosystems impacted by artisanal and small-scale gold mining.

Mercury (Hg) endangers human and wildlife health globally, primarily due to its release from artisanal small-scale gold mining (ASGM). During gold extraction, Hg is emitted into the environment and converted to highly toxic methylmercury by microorganisms. In Madre de Dios (MDD), Peru, ASGM dominates the economy and has transformed rainforests into expansive deforested areas punctuated by abandoned mining ponds. The aim of this study was to evaluate the use of bats as bioindicators for mercury pollution intensity in tropical terrestrial ecosystems impacted by ASGM. We collected 290 bat fur samples from three post-ASGM sites and one control site in Madre de Dios. Our results showed a wide Hg distribution in bats (0.001 to 117.71 mg/kg) strongly influenced by feeding habits. Insectivorous and piscivorous bats from ASGM sites presented elevated levels of Hg surpassing the mercury small mammal threshold for small mammals (10 mg/kg). We observed the highest reported fur mercury concentrations for insectivorous Neotropical bats reported to date (Rhynchonycteris naso, 117 mg/kg). Our findings further confirm that Hg emissions from ASGM are entering local food webs and exposing wildlife species at several trophic levels to higher levels of Hg than in areas not impacted by mining. We also found that three bat genera consistently showed increased Hg levels in ASGM sites relative to controls indicating potential usefulness as bioindicators of mercury loading in terrestrial ecosystems impacted by artisanal and small-scale gold mining.

Environment Degradation, Health Threats, and Legality at the Artisanal Small-Scale Gold Mining Sites in Indonesia.

Artisanal Small-scale Gold Mining (ASGM) activities, despite offering numerous economic incentives, inflict negative impacts on the environment and public health due to the use of mercury or cyanide. This study aims to compare three ASGM locations in Indonesia in terms of environmental impacts and potential health problems in the community. As part of this research, field surveys at three ASGM illegal locations with different conditions, observations, literature studies, and interviews with the community and stakeholders were conducted. At each of the survey sites, the potential threat to public health due to the use of mercury was determined to be high. Additionally, many of the environmental impacts detected were deemed to have reached a high-alert stage, in some cases even posing a level of extreme danger. Based on these results, it has become clear that a form of mining management which reduces the negative impacts on the surrounding environment and community health is needed. The suggestions put forward in this paper, including the call for greater control of ASGM, may also be applied in other developing countries which suffer from similar problems and conditions.

Assessing the suitability of convolutional auto encoder as an unsupervised tool for image classification in artisanal small-scale gold mining environment

Efforts to control or stop illegal Artisanal Small-Scale Gold Mining (ASGM) in Ghana, which is causing significant environmental degradation, have faced numerous challenges because these illegal activities are carried out in remote areas, inaccessible by the current practice of using 4WD vehicles or trekking by foot. This paper sought to assess the suitability of using an Unmanned Aerial Vehicle (UAV) to capture the locations and features of all ASGM sites and use a Convolutional Autoencoder (CAE) to classify the defined sites into legal and illegal ASGM sites. The classification process used by the CAE involved three main stages, namely encoding, latent space learning, and decoding. The encoder accepts the UAV captured images as input, processes the input images to extract salient features and the decoder decodes the salient features to reconstruct the input image and define a site as an ASGM site. To classify a defined ASGM site as legal or illegal, a python program was integrated into the CAE which makes use of known point coordinates of all legal ASGM sites. A site is flagged as illegal if its point coordinates do not match those in the legal ASGM sites database, otherwise, it is a legal site. The performance of the CAE was measured using the following performance metrics: accuracy, precision, recall, and FI-score. The results of the CAE proved superior giving a classification accuracy of 97.52% when compared with the results obtained from other classification algorithms, namely Random Forest (RF) and Support Vector Machine (SVM) with 93.23% and 95.66% respectively. In this paper, it has been demonstrated that UAVs can be used to capture the locations and features of all ASGM sites, which otherwise would have been inaccessible by the use of 4WD vehicles or trekking, and classify the captured location into legal and illegal ASGM sites using a CAE, to facilitate the control and prevention of illegal ASGM in Ghana.

Effects of forest fires on mercury accumulation in soil at the artisanal small-scale gold mining.

In response to the Minamata Convention on Mercury, international organizations, governments, nonprofit organizations, and other institutions as well as individuals have worked to promote the development and implementation of safe and environmentally healthy practices, processes, and products. It is expected that the accumulation of mercury in the natural environment will decrease in volume each year. However, even after Hg ceases to be used, the Hg already accumulated in forests will continue to pose an ecological risk. Forest fires are serious events, partly because they release accumulated Hg from the environment. In this study, the effects of forest fires on the accumulation and chemical species of Hg in soil, related to the mobilization of Hg, were investigated. The research was conducted in secondary forests located near artisanal small-scale gold mining sites, where Hg is used for the amalgamation of gold in Camarines Norte, Philippines. The results showed that the original Hg accumulation level in the burned forest was not as high as that in the control forest, and that burn severity might have affected only the surface soil (0-5cm). However, the proportion of water-soluble Hg, which was derived from ash, was increased by fire. Therefore, it is suggested that forest fires not only increase the release of Hg into the atmosphere but also increase the outflow risk to the aquatic system through rainfall.

Comparative methods for predicting cyanide pollution in artisanal small-scale gold mining catchment by using logistic regression and kriging with GIS

It has been reported that persistent cyanide pollution occurs in artisanal small-scale gold mining (ASGM) catchment areas in Burkina Faso. In the present study, logistic regression (LR) and Regression Kriging (RK) methods were applied to predict cyanide pollution hazard at the catchment level as well as to determine the most vulnerable areas to prioritize for restoration of degraded ecosystems. Soil samples were collected from two ASGM sites in Burkina Faso: the northern Zougnazagmiline site and the southern Galgouli site. Free cyanide (FCN) concentration in each sample was measured and the use of the LR and RK methods identified the relationships between pollution sources and pathways. However, RK was able to identify more areas with a high cyanide hazard than LR. Nevertheless, the two methods reveal that the cyanidation zones and catchments outlets within the two catchments are where the highest risk of cyanide pollution occurs, with probabilities of 0.8 and 1 in Zougnazagmiline and Galgouli, respectively.

Mercury concentrations in paddy field soil and freshwater snails around a small-scale gold mining area, West Java, Indonesia

To estimate the impact of mercury released from an artisanal small-scale gold mining (ASGM) activities on the ecosystem. Total and organic mercury concentrations in paddy field soil and freshwater snails around an artisanal small-scale gold mining area were investigated. Paddy field soil samples and freshwater snails were collected from ten sites along the Cikaniki River. A site located in a national park, which was approximately 12 km upstream from the ASGM site, was considered the reference site for this study. The organic mercury concentration in soil samples collected at the ASGM site was n.d.–0.018 mg kg−1 and that at the reference site was 0.005–0.008 mg kg−1. The organic mercury concentrations in the freshwater snails collected at the ASGM and reference sites were 0.38 ± 0.21 mg kg−1 (31.0 ± 26.6% of total mercury, n = 38) and 0.056 ± 0.032 mg kg−1 (40.5 ± 11.5% of total mercury, n = 16), respectively. Although the original form of mercury in the mining waste was elemental mercury and/or Hg2+, the mercury form changed to organic mercury in environment and the organic mercury was concentrated two orders of magnitude, even in low-order organisms.

Impact of recent artisanal small-scale gold mining in Senegal: Mercury and methylmercury contamination of terrestrial and aquatic ecosystems

In Senegal, the environmental impact of artisanal small-scale gold mining (ASGM) using mercury (Hg) is poorly documented despite its intensification over the past two decades. We report here a complete dataset including the distribution and speciation of Hg in soil, sediment, and water in pristine and ASGM impacted sites of the Gambia River ecosystem (Kedougou region - eastern Senegal). Selective extraction showed that soils surrounding ASGM activities were contaminated with elemental Hg [Hg(0)] at concentrations up to 3.9 mg kg−1. In the Gambia River, high total Hg (THg: 1.16 ± 0.80 mg kg−1) and methylmercury (MeHg: 3.2 ± 2.3 ng g−1) were also measured in sediment samples collected at ASGM sites. Along the stream, THg concentrations in sediment decrease with distance from the ASGM sites, while those of methylmercury increase downstream. The study of THg and MeHg partitioning between filtered surface water and suspended particles demonstrate that particulate transport is responsible for the downstream dissemination of the Hg contamination from ASGM sites. Sedimentation of fine particles enriched in Hg downstream ASGM sites likely favors MeHg production and accumulation in sediment. Although elemental Hg is weakly labile, surface soil erosion may also provide important and long-term Hg inputs to downstream aquatic ecosystems, where it can be oxidized and methylated. Finally, the dissemination of THg and MeHg downstream from the ASGM sites in the Gambia River may constitute a long-term source of contamination and can have a large scale impact on the aquatic ecosystem through biomagnification.

Risk of Mercury Exposure from Fish Consumption at Artisanal Small-Scale Gold Mining Areas in West Nusa Tenggara, Indonesia.

Background.The primary environmental risk associated with artisanal small-scale gold mining (ASGM) activities in Sekotong and Taliwang is waste discharged directly into the environment. This waste contains variable concentrations of heavy metals and a high level of mercury. When these elements are released into the environment, plants and animals can be contaminated. If mercury is methylated to methylmercury, levels can increase in concentration at each level of the food chain (biomagnify). Fish are a primary risk vector for methylmercury poisoning in humans, and represent a significant source of protein for the Sekotong and Taliwang communities.Objectives.The present study aimed to identify the concentration of mercury in fish from ASGM sites in Sekotong and Taliwang.Methods.Descriptive research was used to describe the mercury concentrations of fish in the present study. The fish species collected for the samples represented commercially available fish most commonly consumed by the community on a daily basis.Results.In Sekotong's ASGM area, the mercury concentration in Pilsbryoconcha exilis tissue was 596 ppb, 721 ppb for Sephia officinalis and 50% of the Euthynnus affinis samples had a high level of mercury, above the World Health Organization (WHO) maximum permissable limit for the sale of fish for human consumption of 0.5 ppb.Conclusions.Some fish species from the studied ASGM sites had high mercury concentrations above the maximum permissible mercury concentration in edible fish tissue. The risks associated with mercury exposure from fish consumption threaten community health.Ethics Approval.All experiments were performed in accordance with relevant local guidelines and regulations.Competing Interests.The authors declare no competing financial interests.

Prediction model for cyanide soil pollution in artisanal gold mining area by using logistic regression

It has been reported that persistent cyanide pollution occurs in artisanal small-scale gold mining (ASGM)-affected catchment areas in Burkina Faso. In the present study, the logistic regression method was employed to identify the factors that influence the spatial distribution of cyanide pollution as well as to predict the cyanide pollution map risk at catchment level. Soil samples were collected from two ASGM sites in the northern Zougnazagmiline (“North”) site and southern Galgouli (“South”) site parts of Burkina Faso, covering areas of 22km2 and 20km2, respectively. Free cyanide concentration in each sample was measured. It was shown that the spatial distribution of cyanide was solely controlled by the soil type in Zougnazagmiline and both the soil type and electric conductivity in Galgouli. On the other hand, the cyanidation zones within the two catchments were the places where the highest risk of cyanide pollution occurs, with probabilities of 0.8 and 1 in Zougnazagmiline and Galgouli, respectively. >20% of the settled area in the Zougnazagmiline and 5% of that in Galgouli were exposed to cyanide pollution. Logistic regression was able to reliably predict cyanide contamination in areas affected by ASGM. The model could be useful for decision-makers to plan ASGM-site decontamination.

Anthropometric Characteristics and Mineral Distribution and Contamination in Artisanal Small-scale Gold Mining Site of Ciguha in Gunung Pongkor, Bogor

Ciguha in Gunung Pongkor, Bogor, had been an artisanal and small-scale gold mining site (ASGM) since 1998 where amalgamations were used intensively leading to pollution in water, soil, and foodstuffs. The present study assessed distribution and contamination level (CL) of minerals in a total of 69 environmental samples consisting of drinking water (n = 12), rice (n = 13), vegetable (n = 15), fruits (n = 5), fish (n = 14), and soil (n = 10). Chromium, iron, and manganese representing trace essential elements but toxic at high level, mercury representing heavy metal, arsenic representing toxic metalloid, and selenium representing essential metalloid which toxic at high level, were analyzed as mineral contaminants. Meanwhile, a total of 101 Ciguha residents consisting of 60 adults, 15 teenagers, and 26 school aged children were involved to charaterize athropometric exposure factors. The results shows that mercury has polluted soil, kangkung, thai squash, cassava leaves, and rice with contamination level (CL) of 604.43, 8.15, 6.01, 4.14, and 2.76 folds, respectively, while chromium has only polluted thai squash with CL of 1.18 folds. Amazingly, mercury distribution was only in the third position after iron and manganese, while the most distributed mineral was iron and the least was selenium. In overall environmental matrices, the detection frequencies of iron, manganese, mercury, chromium, arsenic, and selenium were 94.2, 56.2, 52.2, 47.8, 21.7, and 15.9 %, respectively. In conclusion, mercury was the most critical contaminant in ASGM site of Ciguha that has heavily polluted soil and grown vegetables, but the most distributed mineral was iron. Toxicologically, only mercury and chromium are important while arsenic, iron, manganese, and selenium are of less concern since the CL<1.

Geochemistry and mercury contamination in receiving environments of artisanal mining wastes and identified concerns for food safety

Artisanal small-scale gold mining (ASGM) using mercury (Hg) amalgamation has been occurring on Buru Island, Indonesia since early 2012, and has caused rapid accumulation of high Hg concentrations in river, estuary and marine sediments. In this study, sediment samples were collected from several sites downstream of the Mount Botak ASGM site, as well as in the vicinity of the more recently established site at Gogrea where no sampling had previously been completed. All sediment samples had total Hg (THg) concentrations exceeding Indonesian sediment quality guidelines and were up to 82 times this limit at one estuary site. The geochemistry of sediments in receiving environments indicates the potential for Hg-methylation to form highly bioavailable Hg species. To assess the current contamination threat from consumption of local seafood, samples of fish, molluscs and crustaceans were collected from the Namlea fish market and analysed for THg concentrations. The majority of edible tissue samples had elevated THg concentrations, which raises concerns for food safety. This study shows that river, estuary and marine ecosystems downstream of ASGM operations on Buru Island are exposed to dangerously high Hg concentrations, which are impacting aquatic food chains, and fisheries resources. Considering the high dietary dependence on marine protein in the associated community and across the Mollucas Province, and the short time period since ASGM operations commenced in this region, the results warrant urgent further investigation, risk mitigation, and community education.

Human exposure to mercury in artisanal small-scale gold mining areas of Kedougou region, Senegal, as a function of occupational activity and fish consumption.

We investigated mercury (Hg) exposure of food web and humans in the region of Kedougou, Senegal, where Hg is used for gold amalgamation in artisanal small-scale gold mining (ASGM). For this purpose, total mercury (THg) concentration was determined in eight fish species and two shellfish species from Gambia River and in human hair from 111 volunteers of different age and sex, living in urban locations (Kedougou and Samekouta) or in ASGM areas (Tinkoto and Bantako). THg concentrations in fish samples range from 0.03 to 0.51 mg kg(-1) wet weight (ww) and 0.5 to 1.05 mg kg(-1) ww for shellfish. THg concentrations in fish are below the WHO guideline of 0.5 mg kg(-1) ww, whereas 100 % of shellfish are above this safety guideline. In the entire set of fish and shellfish samples, we documented a decrease of THg concentrations with increasing selenium to mercury (Se:Hg) ratio suggesting a protection of Se against Hg. However, local population consuming fish from the Gambia River in the two ASGM areas have higher THg concentrations (median = 1.45 and 1.5 mg kg(-1) at Bantako and Tinkoto) in hair than those from others localities (median = 0.42 and 0.32 mg kg(-1) at Kedougou town and Samekouta) who have diverse diets. At ASGM sites, about 30 % of the local population present Hg concentrations in hair exceeding 1 mg kg(-1), defined as the reference concentration of Hg in hair. We also evidence a higher exposure of women to Hg in the Tinkoto ASGM site due to the traditional distribution of daily tasks where women are more involved in the burning of amalgams. The discrepancy between the calculated moderate exposure through fish consumption and the high Hg concentrations measured in hair suggest that fish consumption is not the only source of Hg exposure and that further studies should focus on direct exposure to elemental Hg of population living at ASGM sites.

Effect of recent artisanal small-scale gold mining on the contamination of surface river sediment: Case of Gambia River, Kedougou region, southeastern Senegal

We report here the first inventory of mercury (Hg) contamination in the region of Kedougou, Senegal, where mercury (Hg) is used for gold amalgamation in artisanal small-scale gold mining (ASGM) activities. Sediment cores were sampled during the dry and wet seasons, and at different locations along the Gambia River in the Kedougou region to evaluate the spatio-temporal trends of Hg distribution related to ASGM activities. The sediment samples were analysed for total mercury and trace element concentrations (Cr, Cu, Zn, Pb, As, and Sc). The results highlight high concentrations of total Hg (reaching up to 9.9mgkg−1) in sediment cores sampled in the vicinity of ASGM operations, with the highest values reported for the dry season. The calculation of the Hg Enrichment Factor (EF) using Sc as refractory element confirms high enrichments around active sites of gold mining being proportional to the density of miners and the duration of mining activities. The Hg spatial distribution reveals a very local contamination and a limited downstream dispersion of the contaminant. The high Hg concentrations obtained at ASGM sites largely exceed the Sediment Quality Guidelines (SQGs) and the Probable effect concentration (PEC) for the Protection of Aquatic Life recommendation. Our results demonstrate that the ASGM activities discharged large amounts of Hg into the Gambia River ecosystem and that the accumulation of Hg in sediments may represent a significant human health risk and a potential source of toxicity for aquatic organisms.

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.