Artisanal And Small-scale Gold Mining Sites Research Articles

Mercury Levels in Hair of Pregnant Women in Tumbes, Peru: A Cross-Sectional Study.

Mercury, a potent toxin that poses serious risks to human health, particularly for pregnant women and young children, is widely present due to artisanal and small-scale gold mining (ASGM), which impacts water quality. The objective of this study was to evaluate methylmercury exposure among pregnant women in communities downstream from ASGM sites. We characterized hair total mercury (THg) concentrations among 148 pregnant women across 24 communities in the Tumbes region of Peru, downstream from ASGM sites in Ecuador. Using purposeful sampling, we classified communities into three exposure risk zones: Puyango-Tumbes River watershed, Coast, and Zarumilla. The mean THg concentration was 2.08 µg/g ± 1.36, with 45% of participants (67/148) exceeding UNEP/WHO exposure limits (>2.0 µg/g). The median was 1.84 with an interquartile range (IQR) from 1.01 to 2.83. Median THg levels were significantly higher in the Puyango-Tumbes River region (2.72 µg/g; IQR: 1.66-3.55) compared with Zarumilla (1.61 µg/g; IQR: 0.67-2.63; P = 0.001) and to the Coast (1.71 µg/g; IQR: 1.13-2.50; P = 0.01), suggesting that living close to the Puyango-Tumbes River may be associated with a higher mercury exposure risk. After controlling for potential confounders, individuals in the Puyango-Tumbes watershed exhibited a significant 57% higher expected geometric mean of hair THg compared with Zarumilla (95% CI: 0.1-146.2%). These findings underscore the importance of identifying high-risk regional populations and ongoing biomonitoring of the Puyango-Tumbes River watershed.

Elevated mercury exposure in bird communities inhabiting Artisanal and Small-Scale Gold Mining landscapes of the southeastern Peruvian Amazon.

Artisanal and Small-Scale Gold Mining (ASGM) represents a significant source of anthropogenic mercury emissions to the environment, with potentially severe implications for avian biodiversity. In the Madre de Dios department of the southern Peruvian Amazon, ASGM activities have created landscapes marred by deforestation and post-mining water bodies (mining ponds) with notable methylation potential. While data on Hg contamination in terrestrial wildlife remains limited, this study measures Hg exposure in several terrestrial bird species as bioindicators. Total Hg (THg) levels in feathers from birds near water bodies, including mining ponds associated with ASGM areas and oxbow lakes, were analyzed. Our results showed significantly higher Hg concentrations in birds from ASGM sites with mean ± SD of 3.14 ± 7.97 µg/g (range: 0.27 to 72.75 µg/g, n = 312) compared to control sites with a mean of 0.47 ± 0.42 µg/g (range: 0.04 to 1.89 µg/g, n = 52). Factors such as trophic guilds, ASGM presence, and water body area significantly influenced feather Hg concentrations. Notably, piscivorous birds exhibited the highest Hg concentration (31.03 ± 25.25 µg/g, n = 12) exceeding known concentrations that affect reproductive success, where one measurement of Chloroceryle americana (Green kingfisher; 72.7 µg/g) is among the highest ever reported in South America. This research quantifies Hg exposure in avian communities in Amazonian regions affected by ASGM, highlighting potential risks to regional bird populations.

Poison in the nursery: Mercury contamination in the tadpole-rearing sites of an Amazonian frog

Artisanal and small-scale gold mining (ASGM) has become a major threat for Neotropical forests. This technique for obtaining gold is a substantial driver of small-scale deforestation and the largest contributor of Hg emissions to both the atmosphere and freshwater systems globally. Previous studies have demonstrated the impacts of Hg accumulation on various aquatic ecosystems and organisms. However, its consequences in other, more discrete systems such as phytotelmata (water-holding plant structures), and the organisms therein, have so far gone unnoticed. Here, we show high concentrations of Hg (mean ± SD: 1.43 ± 2.19 ppm) in phytotelmata and other small pools, the aquatic microenvironments used by the Neotropical poison frog Dendrobates tinctorius as tadpole-rearing sites. In 17 % of the cases, we detected Hg concentrations above the severe effect level (SEL = 2 ppm) for freshwater sediments. Hg concentrations varied depending on pool characteristics and tended to increase in proximity to known ASGM sites. We did not find an effect of Hg concentration on the number of D. tinctorius tadpoles in a given pool. Tadpoles were found in pools with concentrations of up to 8.68 ppm, suggesting that D. tinctorius fathers do not avoid pools with high Hg levels for tadpole deposition. While further research is needed to determine the potential effects of Hg on tadpole development, we found an intriguing tendency for tadpoles in later developmental stages to have lower body condition when occurring in pools with higher Hg concentrations. Our findings provide evidence of relevant Hg concentrations in the terrestrial water systems used by phytotelm-breeding anurans, and highlight the need of further field and experimental studies investigating the implications of Hg contamination for tadpole development and behaviour and the overall conservation of Amazonian biodiversity.

Contamination Level in Geo-Accumulation Index of River Sediments at Artisanal and Small-Scale Gold Mining Area in Gorontalo Province, Indonesia.

Substances found in watersheds and sediments in artisanal and small-scale gold mining (ASGM) areas contaminated by heavy metals are becoming tremendously critical issues in Asia. This study aimed at clarifying the pollution caused by heavy metals in sediments in river basins near ASGM sites in Gorontalo Province, North Sulawesi, Indonesia. Sediment samples collected from experimental areas were classified into nine clay samples and twenty-seven sand samples, whereas three other samples were collected from the control area. Particle-induced X-ray emission was used to analyze these samples. The Statistical Package for the Social Science and the geo-accumulation index (Igeo) were also used for analysis. Based on the results, Hg, Pb, As, and Zn had a concentration of 0–334 µg/g, 5.5–1930 µg/g, 0–18,900 µg/g, and 0–4923.2 µg/g, respectively, which exceeded limits recommended by the U.S. Environmental Protection Agency consensus (1991) and the Indonesian Government Regulation Number 38, 2011. Furthermore, Igeo showed the order of the pollution degree Hg < Zn < Pb < As and reflected an environment contaminated by heavy metals, ranging from unpolluted to extremely polluted areas. Therefore, sediments contaminated by Hg, Pb, As, and Zn could be found along the river basin of mining areas.

“Doing ASGM without mercury is like trying to make omelets without eggs”. Understanding the persistence of mercury use among artisanal gold miners in Burkina Faso

Researchers and policymakers are concerned with the uncontrolled use of mercury in artisanal and small-scale gold mining (ASGM). Despite the availability of alternative technologies, mercury is still the first choice to separate gold from ore on most ASGM sites. Taking the case of Burkina Faso, this mixed methods study contributes to understanding the continued use of mercury by analyzing the non-technical functions that mercury accomplishes. Applying a political ecology lens, we analyze the mechanisms that actors deploy to access benefits from ASGM and manage business-related risks, revealing dependencies on webs of power that govern the informal setting of the ASGM value chain from production to export. Our results challenge conventional wisdom about poverty-driven ASGM. We demonstrate that the sector is not simply propelled by jobless rural youth and poor farmers eager to make a lucky strike. Instead, the need of ASGM for prefinancing extraction made it as much the product of capital looking for lucrative investment. The business model of investors is based on prefinancing extraction, controlling access to market, and taking advantage of excess labor by shifting operational and financial risks upstream. In an entirely informal scheme of cascading prefinancing arrangements, mercury serves as a ‘commitment and controlling device.’ The provision of mercury guarantees that the financier can access the gold at the exact moment of recovery, regain the loan, and secure the return on investment. Phasing out mercury will remain a challenge as long as it is used as a social control device.

Environmental Survey of the Distribution and Metal Contents of Pteris vittata in Arsenic-Lead-Mercury-Contaminated Gold Mining Areas along the Bone River in Gorontalo Province, Indonesia.

In this paper, we report ecological and environmental investigations on Pteris vittata in the As–Pb–Hg-polluted Bone River area, Gorontalo Province, Indonesia. The density distribution of P. vittata decreases from around the artisanal and small-scale gold mining (ASGM) site to the lower reaches of the Bone River, and it is rarely found near Gorontalo City. The maximum concentrations of As, Hg, and Pb recorded in the soil samples were 401, 36, and 159 mg kg−1, respectively, with their maximum concentrations in P. vittata recorded as 17,700, 5.2, and 39 mg kg−1, respectively. Around the ASGM sites, the concentrations of As, Pb, and Hg in P. vittata were highest in the study area. These data suggest that P. vittata, a hyperaccumulator of As, may be useful as a bioindicator for assessing environmental pollution by Pb and Hg.

Mercury Contamination in Selected Edible Plants and Soil from Artisanal and Small-scale Gold Mining in Sukabumi Regency, Indonesia

Artisanal and small-scale gold mining (ASGM) activities often pollute soil, water, and air, thereby achieving widespread proliferation, and contaminating the surrounding biota including plants. Mercury contamination on agricultural land around ASGM areas has been widely reported. This study aims to determine the total mercury contamination in plants and soil around active ASGM sites in Sukabumi Regency, Indonesia, namely, Waluran, Lengkong, and Ciemas Districts. Total mercury (Hg) content was measured from 27 plant samples (including cassava [Manihot utilisima], rice [Oryza sativa], and papaya [Carica papaya]), 7 rhizosphere soil samples, and 7 non-rhizosphere soil samples. Data were analyzed using Kruskal–Wallis test. Results showed no significant difference in total mercury concentrations among locations or plant parts, between rhizosphere and non-rhizosphere soils (p > 0.05), and among cassava plant parts, papaya, and rice. The highest mercury level was found in cassava (0.33–43.27 ppm). Mercury contamination in rice and papaya was relatively low at 0.03–1.22 and 0.06–5.11 ppm, respectively. According to the Regulation of the Head of BPOM of the Republic of Indonesia Number 23 of 2017 concerning the Maximum Limit of Heavy Metal Contamination in Processed Food, 0.03 ppm is the maximum limit of mercury contamination in fruits, vegetables, and cereals. Therefore, all plant samples around the ASGM sites have exceeded the maximum mercury contamination and thus are not suitable for consumption.

Assessment of dissolved mercury by diffusive gradients in thin films devices in abandoned ponds impacted by small scale gold mining

In order to fulfil the Minamata Convention on Mercury, it is necessary to monitor the Hg contamination in freshwater ecosystems nearby artisanal and small scale gold mining (ASGM) areas. Since most of these ASGM communities are located in remote areas, a convenient method for sampling, preserving and transporting samples is needed. In this study we evaluated the feasibility of the diffusive gradient in thin-films (DGT) technique to detect and quantify the labile fraction of Hg and other metals (Pb, Cu, Zn, Cd, Ni, Mn and Cr) in a hard-to-reach gold mining district in the state of Chocó, Colombia. We deployed DGT at sampling sites along the Atrato river and abandoned mining ponds (AMPs) which were deserted in different periods since 1997 to 2019 (6–15 years). In average, the labile THg concentrations in AMPs (148.9 ± 43.2 ng L−1) were a 50% higher than in the river water (99.9 ± 37.4 ng L−1). In the ponds, no significant differences were found in labile Hg with respect abandonment period. Labile Ni (0.9–493.1), Mn (1.33–11.48), Cu (0.030–2.233), and Zn (0.67–10.29) (in μg L−1) were found in higher amounts than for the rest of metals. Labile concentrations of metals are related with their downstream proximity to gold mining activities, being higher in devices deployed close to ASGM sites. Moreover, this study demonstrates the feasibility of the DGT technique to sample, transport, storage, and preserve labile Hg from hard-to-reach ASGM areas.

Time-Series Assessment of Camp-Type Artisanal and Small-Scale Gold Mining Sectors with Large Influxes of Miners Using LANDSAT Imagery

Mining sites development have had a significant impact on local socioeconomic conditions, the environment, and sustainability. However, the transformation of camp-type artisanal and small-scale gold mining (ASGM) sites with large influxes of miners from different regions has not been properly evaluated, owing to the closed nature of the ASGM sector. Here, we use remote sensing imagery and field investigations to assess ASGM sites with large influxes of miners living in mining camps in Bone Bolango Regency, Gorontalo Province, Indonesia, in 1995–2020. Built-up areas were identified as indicators of transformation of camp-type ASGM sites, using the Normalized Difference Vegetation Index, from the time series of images obtained using Google Earth Engine, then correlated with the prevalent gold market price. An 18.6-fold increase in built-up areas in mining camps was observed in 2020 compared with 1995, which correlated with increases in local gold prices. Field investigations showed that miner influx also increased after increases in gold prices. These findings extend our understanding of the rate and scale of development in the closed ASGM sector and the driving factors behind these changes. Our results provide significant insight into the potential rates and levels of socio-environmental pollution at local and community levels.

Mapping Artisanal and Small-Scale Gold Mining in Senegal Using Sentinel 2 Data.

Artisanal and small‐scale gold mining (ASGM) represents a significant economic activity for communities in developing countries. In southeastern Senegal, this activity has increased in recent years and has become the main source of income for the local population. However, it is also associated with negative environmental, social, and health impacts. Considering the recent development of ASGM in Senegal and the difficulties of the government in monitoring and regulating this activity, this article proposes a method for detecting and mapping ASGM sites in Senegal using Sentinel 2 data and the Google Earth Engine. Two artisanal mining sites in Senegal are selected to test this approach. Detection and mapping are achieved following a processing pipeline. Principal component analysis (PCA) is applied to determine the optimal period of the year for mapping. Separability and threshold (SEaTH) is used to determine the optimal bands or spectral indices to discriminate ASGM from other land use. Finally, automatic classification and mapping of the scenes are achieved with support vector machine (SVM) classifier. The results are then validated based on field observations. The PCA and examination of spectral signatures as a function of time indicate that the best period for discriminate ASGM sites against other types of land use is the end of dry season, when vegetation is minimal. The classification results are presented as a map with different categories of land use. This method could be applied to future Sentinel scenes to monitor the evolution of mining sites and may also be extrapolated to other relevant areas in the Sahel.

Dried blood spots to characterize mercury speciation and exposure in a Colombian artisanal and small-scale gold mining community

The artisanal and small-scale gold mining (ASGM) sector uses the most mercury (Hg) worldwide. Despite health concerns associated with high Hg exposures in these communities, ASGM sites are often situated in resource limited and remote regions which challenge traditional human biomonitoring approaches. To help overcome such challenges, here we report on the development of a high-quality method to characterize chemical speciation of Hg in dried blood spots (DBS), and then apply this method to assess Hg exposures in people sampled from an ASGM community (Pueblito Mejia) and a nearby town (Barranco de Loba) in Colombia. We collected DBS and urine samples from 35 individuals in 2018, and used these to assess occupational (DBS inorganic Hg (InHg) and urine total Hg (THg) measures) and environmental (DBS methylmercury (MeHg) measures) exposure of participants to different forms of Hg. The accuracy and precision of the DBS-based measures generally met assay performance guideline. In study participants, the mean concentrations of DBS MeHg, InHg, and THg, and urine THg were 1.9, 4.1, 6.0, and 3.1 μg/L, respectively. For 37% of the participants, DBS THg values exceeded the 5 μg/L ‘alert level’ proposed by the German HBM Commission. About 60% of the blood Hg was in the InHg form thus exemplifying a need to speciate Hg in blood sampled from ASGM sites to better understand the contributions of environmental and occupational exposure sources. This study demonstrates the feasibility of using DBS for Hg speciation exposure assessments in remote and resource-limited areas such as ASGM communities.

Spatial Analysis of Artisanal and Small-Scale Mining in the Tarkwa-Nsuaem Municipality of Ghana

Abstract&#x0D; In recent times there have been lots of public outcry on the environmental and public health and safety effects of Artisanal and Small-scale gold Mining (ASM) and the need to monitor ASM activities for reclamation purposes. To effectively develop and deploy policy responses to the environmental and human health effects of ASM, knowledge of the locations and distribution of ASM sites is a prerequisite. However, information regarding ASM hotspots and spatial distribution, the scope and types of ASM operations are hard to find. Therefore, this research was designed to use satellite-based data to map out ASM sites, focusing on the Tarkwa-Nsuaem municipality as the study area. Several image processing techniques were applied on a Landsat 8 satellite image downloaded from the US Geological Survey website. The image processing resulted in the identification of 221 clusters of ASM sites, representing 12.72% of the total size of the study area. To further explore the effects of these ASM sites, Areas of Interest (AOI) including forest reserve, rivers, large-scale mines and urban settlements were defined. By selecting and analysing the location and distribution of the ASM sites in relations to the AOI, the study was effective in identifying environmentally sensitive and critical areas warranting the urgent attention of society to mitigate the health, safety and ecosystem service effects of ASM in the study area. By identifying the environmental sensitive areas being affected by ASM, the findings could support the prioritisation of reclamation efforts.&#x0D; &#x0D; Keywords: Artisanal Small-Scale Mining, Satellite Image, Environmental Effect, Public Health and Safety

Distribution of total and organic mercury in soils around an artisanal and small-scale gold mining area in West Java, Indonesia

This study was conducted to understand the environmental behavior of mercury released by artisanal and small-scale gold mining (ASGM) activities. For this purpose, we attempted to assess the effect of diffused mercury on mercury concentrations in soil, demonstrate the presence of methylmercury in soil affected by the deposited mercury and determine the reactions associated with methylmercury production. The vertical profiles of mercury were obtained from two sites in the forest of the ASGM village in Pongkor (West Java, Indonesia) and from two sites in Mount Halimun-Salak National Park, which is approximately 12 km from the ASGM village. The highest total mercury concentration, 8.9 mg kg−1, was observed for soil samples collected at the ASGM village. The mercury was concentrated at the surface or in the subsurface layers, and the concentrations were several times to more than ten times higher than the lowest values observed in the deeper layers at each site. Even in the national park, the highest concentration of 1.9 mg kg−1 was observed in the upper soil layer. These results suggest that the primary source of mercury in the forest soil is atmospheric deposition; fallen plant leaves also deliver accumulated mercury to the soil surface. The organic mercury percentages of the total mercury were 0.2 ± 0.1% for the national park and 0.3 ± 0.2% for ASGM sites. The vertical variation in organic mercury concentration did not always match that in total mercury concentration, which suggested that the formation of methylmercury in soil was closely related to the decomposition of organic matter near the surface. The soil surface is an important reaction field for methylmercury production in forested areas.

Artisanal and small-scale gold mining, meandering tropical rivers, and geological heritage: Evidence from Brazil and Indonesia

Artisanal and small-scale gold mining (ASGM) flourishes along many tropical rivers, and it still requires proper documentation in many countries, as well as interpretation in terms of rational resource exploitation and wildlife preservation. In this study we used remote sensing techniques to analyze two representative examples of ASGM: one along the Marupa River in Brazil (Tapajós Domain) and another one along the Kahayan River in Indonesia (Central Kalimantan). The documented spatial extent of ASGM is ~9175km2 along the Marupa River and ~30,427km2 along the Kahayan River. It was established these activities change rapidly (2-3years) in space. Although active and inactive sites occur in both areas, a great number of inactive sites distinguish the Marupa River. It is very crucial that ASGM along the Marupa and Kahayan rivers link strongly to watercourse meanders, but also changes river valley morphology. This is an interesting evidence of coupled fluvial-anthropic morphodynamics of meandering river valleys. Geological phenomena represented in the study areas include gold resource exploitation (economic phenomenon), landforms and their dynamics (geomorphological phenomenon), and mercury environmental pollution (geochemical phenomenon). Due to remarkable spatial extent and evident interconnection, these phenomena seem to be unique and, thus, constituting geological heritage. Identification of the latter means that ASGM sites add value to the local environment. A paradox is that illegal and mercury-releasing ASGM needs termination, but such an action will result in the loss of the noted geological heritage value. Solution to this paradox requires careful development of plans for local management. However, it is clear that the presence of the noted heritage requires turning more attention to ASGM and their natural (river valley) context.

Potential health effects of cyanide use in artisanal and small-scale gold mining in Burkina Faso

Abstract The artisanal and small-scale gold mining (ASGM) sector in Burkina Faso increasingly employs cyanide leaching to exploit the natural resource gold. The long-term consequences of chronic cyanide exposure in humans have yet to be fully elucidated. Meanwhile, the local health and development actors are facing immediate, unfamiliar challenges. The aim of this study was to deepen the understanding of cyanide exposure pathways, potential human exposure and associated health effects in ASGM communities in order to tailor health promotion and sustainable development recommendations for local actors. In April and May 2017, a cross-sectional epidemiological study was carried out in three ASGM sites in Burkina Faso. Three exposure groups were included: (i) miners using cyanide; (ii) miners who do not use cyanide; and (iii) ASGM community members not directly involved in mining. A questionnaire was administered to all study participants, followed by a finger prick blood sample to determine blood lactate level as a proxy indicator for cyanide exposure. Overall, 279 individuals participated (99 cyanide-using miners, 90 non-cyanide using miners and 90 community members not involved in mining activities). Mean blood lactate levels were significantly higher in miners using cyanide (4.7 mmol/L, 95% confidence interval (CI) 3.8–5.6 mmol/L), compared to non-cyanide using miners (3.4 mmol/L, 95% CI 2.9–3.7 mmol/L) and other community members not involved in mining activities (2.8 mmol/L, 95% CI 2.4–3.2 mmol/L). Multiple linear regression found loss of short-term memory reported by participants associated with higher blood lactate level. In view of our findings, we conclude that the use of cyanide in Burkina Faso’s ASGM sector is associated with potential negative health effects. Hence, specific public health interventions are warranted, such as raising awareness among miners of the risks of cyanide use, promotion of protective measures and strengthening of health sector capacities to recognize and manage mining-related health issues and law enforcement.

Mutualism, commensalism or parasitism? Perspectives on tailings trade between large-scale and artisanal and small-scale gold mining in Ghana

Due to poor technology and lack of proper skills in mineral processing techniques, a greater percentage (about 70%) of gold is lost to the tailings stream in artisanal and small-scale gold mining (ASGM). These tailings, in the last decade, have become a major source of revenue for some large-scale mining (LSM) companies in Ghana because they have advanced technologies to optimize recovery. This paper examines the tailings trade between ASGM and LSM companies in Ghana and determines their associated relationships. It also informs policy decisions regarding gold mining in Ghana. Field visits were made to licensed ASGM sites in the Tarkwa Mining District where the trade is mostly practiced to obtain first-hand information and conduct interviews with diggers. Results indicate that both ASGM operators and LSM companies derive revenue from the tailings trade, exhibiting a relationship that could be described as mutualistic. Based on the tailings price determination, the symbiotic relationship is described as parasitic because the tailings pricing process is largely controlled by the LSM companies to the detriment of the ASGM operators. As a result of the environmental dangers posed by the tailings trade, the interdependency could equally be described as parasitic since both the ASGM operators and the LSM companies benefit to the detriment of the natural ecosystem. It was also observed that while some stakeholders attempt to criminalize the tailings trade, there is presently no law or regulation that prohibits such trade in the Ghanaian mining industry.

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

The largest source of global mercury (Hg) anthropogenic inputs to the environment is derived from artisanal and small-scale gold mining (ASGM) activities in developing countries. While our understanding of global Hg emissions from ASGM is growing, there is limited empirical documentation about the levels of total mercury (THg) and methylmercury (MeHg) contamination near ASGM sites. We measured THg and MeHg concentrations in soil (n = 119), sediment (n = 22), and water (n = 25) from four active ASGM villages and one non-ASGM reference village in Senegal, West Africa. Nearly all samples had THg and MeHg concentrations that exceeded the reference village concentrations and USEPA regulatory standards. The highest median THg concentrations were found in huts where mercury-gold amalgams were burned (7.5 μg/g), while the highest median MeHg concentrations and percent Hg as MeHg were found in river sediments (4.2 ng/g, 0.41%). Median river water concentrations of THg and MeHg were also elevated compared to values at the reference site (22 ng THg/L, 0.037 ng MeHg/L in ASGM sites). This study provides direct evidence that Hg from ASGM is entering both the terrestrial and aquatic ecosystems where it is converted in soils, sediment, and water to the neurotoxic and bioavailable form of MeHg.

Mercury Pollution in Amapá, Brazil: Mercury Amalgamation in Artisanal and Small-Scale Gold Mining or Land-Cover and Land-Use Changes?

Mercury (Hg) poses a public health burden in the Amazon and worldwide. Although usually attributed to Hg used in artisanal and small-scale gold mining (ASGM), the primary source of elevated Hg in Amazonian aquatic ecosystems is contested since there have not been tools to differentiate between Hg from ASGM and Hg from other sources such as increased soil erosion associated with land-cover and land-use change. To directly assess Hg contamination from ASGM, stable Hg isotope analyses were applied to sediment cores, surface sediments, and soils from two aquatic ecosystems in Amapa, Brazil, one downstream of ASGM activities and one isolated from ASGM. Downstream of the ASGM sites, the Hg isotope data is consistent with elevated Hg coming dominantly from increased erosion of soils and not from Hg used during gold extraction. Although these two sources represent different pathways of contamination to downstream ecosystems, ASGM may contribute to both land-cover and land-use change and local contamination of soi...

Screening of native plant species for phytoremediation potential at a Hg-contaminated mining site

Artisanal and small-scale gold mining (ASGM) is the largest sector of demand for mercury (Hg), and therefore, one of the major sources of Hg pollution in the environment. This study was conducted in the Alacrán gold-mining site, one of the most important ASGM sites in Colombia, to identify native plant species growing in Hg-contaminated soils used for agricultural purposes, and to assess their potential as phytoremediation systems. Twenty-four native plant species were identified and analysed for total Hg (THg) in different tissues (roots, stems, and leaves) and in underlying soils. Accumulation factors (AF) in the shoots, translocation (TF) from roots to shoots, and bioconcentration (BCF) from soil-to-roots were determined. Different tissues from all plant species were classified in the order of decreasing accumulation of Hg as follows: roots>leaves>stems. THg concentrations in soil ranged from 230 to 6320ngg−1. TF values varied from 0.33 to 1.73, with high values in the lower Hg-contaminated soils. No correlation was found between soils with low concentrations of Hg and plant leaves, indicating that TF is not a very accurate indicator, since most of the Hg input to leaves at ASGM sites comes from the atmosphere. On the other hand, the BCF ranged from 0.28 to 0.99, with Jatropha curcas showing the highest value. Despite their low biomass production, several herbs and sub-shrubs are suitable for phytoremediation application in the field, due to their fast growth and high AF values in large and easily harvestable plant parts. Among these species, herbs such as Piper marginathum and Stecherus bifidus, and the sub-shrubs J. curcas and Capsicum annuum are promising native plants with the potential to be used in the phytoremediation of soils in tropical areas that are impacted by mining.

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

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.