The Mercury Problem in Artisanal and Small-Scale Gold Mining

In situ remediation of mercury-contaminated groundwater through an in situ created reactive zone enabled by carboxymethyl cellulose stabilized FeS nanoparticles

Faced with worldwide mercury (Hg) contamination in groundwater, efficient in situ remediation technologies are urgently needed. Carboxymethyl cellulose (CMC) stabilized iron sulfide (CMC-FeS) nanoparticles have been found effective for immobilizing mercury in water and soil. Yet, the potential use of the nanoparticles for creating an in situ reactive zone (ISRZ) in porous geo-media has not been explored. This study assessed the transport and deliverability of CMC-FeS in sand media towards creating an ISRZ. The nanoparticles were deliverable through the saturated sand bed and the particle breakthrough/deposition profiles depended on the injection pore velocity, initial CMC-FeS concentration, and ionic strength. The transport data were well interpreted using an advection-dispersion transport model combined with the classical filtration theory. The resulting ISRZ effectively removed mercury from contaminated groundwater under typical subsurface conditions. While the operating conditions are yet to be optimized, the Hg breakthrough time can be affected by groundwater velocity, influent mercury concentration, dissolved organic matter, and co-existing metals/metalloids. The one-dimensional advection-dispersion equation well simulated the Hg breakthrough data. CMC-FeS-laden ISRZ effectively converted the more easily available Hg species to stable species. These findings reveal the potential of creating an ISRZ using CMC-FeS for in situ remediation of Hg contaminated soil and groundwater.

Global threats of extractive industries to vertebrate biodiversity

Mining is a key driver of land-use change and environmental degradation globally, with the variety of mineral extraction methods used impacting biodiversity across scales. We use IUCN Red List threat assessments of all vertebrates to quantify the current biodiversity threat from mineral extraction, map the global hotspots of threatened biodiversity, and investigate the links between species' habitat use and life-history traits and threat from mineral extraction. Nearly 8% (4,642) of vertebrates are assessed as threatened by mineral extraction, especially mining and quarrying, with fish at particularly high risk. The hotspots of mineral extraction-induced threat are pantropical, as well as a large proportion of regional diversity threatened in northern South America, West Africa, and the Arctic. Species using freshwater habitats are particularly at risk, while the effects of other ecological traits vary between taxa. As the industry expands, it is vital that mineral resources in vulnerable biodiversity regions are managed in accordance with sustainable development goals.

"Hg distribution and accumulation in soil and vegetation in areas impacted by artisanal gold mining in the Southern Amazonian region of Madre de Dios, Peru."

Artisanal and small-scale gold mining (ASGM) is the primary global source of anthropogenic mercury (Hg) emissions. It has impacted the Amazon rainforest in the Peruvian region of Madre de Dios. However, few studies have investigated Hg's distribution in terrestrial ecosystems in this region. We studied Hg's distribution and its predictors in soil and native plant species from artisanal mining sites. Total Hg concentrations were determined in soil samples collected at different depths (0-5 cm and 5-30 cm) and plant samples (roots, shoots, leaves) from 19 native plant species collected in different land cover categories: naked soil (L1), gravel piles (L2), natural regeneration (L3), reforestation (L4), and primary forest (L5) in the mining sites. Hg levels in air were also studied using passive air samplers. The highest Hg concentrations in soil (average 0.276 and 0.210 mg kg-1 dw.) were found in the intact primary forest (L5) at 0-5 cm depth and in the plant rooting zones at 5-30 cm depth, respectively. Moreover, the highest Hg levels in plants (average 0.64 mg kg-1 dw) were found in foliage of intact primary forest (L5). The results suggest that the forest in these sites receives Hg from the atmosphere through leaf deposition and that Hg accumulates in the soil surrounding the roots. The Hg levels found in the plant leaves of the primary forest are the highest ever recorded in this region, exceeding values found in forests impacted by Hg pollution worldwide and raising concerns about the extent of the ASGM impact in this ecosystem. Correlations between Hg concentrations in soil, bioaccumulation in plant roots, and soil physical-chemical characteristics were determined. Linear regression models showed that the soil organic matter content (SOM), pH, and electrical conductivity (EC) predict the Hg distribution and accumulation in soil and bioaccumulation in root plants.

Health and environmental risk assessment of mercury in outdoor and indoor dust in artisanal and small-scale gold mining area in Amansie-west district in the Ashanti Region of Ghana

Mercury (Hg) pollution around artisanal and small-scale gold mining (ASGM) areas has been of much concern. Many studies have reported elevated Hg concentrations in environmental media, but studies on dust relating to inhalation exposure of Hg around ASGM area are limited. In this study, we investigated Hg in indoor and outdoor dust to reveal environmental and human health risk around ASGM in Amansie West district, Ghana. Indoor and outdoor dust samples were collected from Manso Abore and Manso Nkwanta in Ashanti Region. Concentration of Hg in the samples were analyzed using a direct Hg analyzer. The mean and median value of Hg concentration in the indoor dust (n = 31) were 2.2 ± 3.6 mg/kg and 0.72 mg/kg respectively while that of the outdoor dust (n = 60) were 0.19 ± 0.48 mg/kg and 0.042 mg/kg, respectively. The mean and median Hg concentration in indoor dust were about 11 and 17 times higher respectively than that in the outdoor dust. The Hg concentration in the indoor dust was statistically significantly higher than that of the non-miner in Manso Abore (p < 0.05) but was not significant in Manso Nkwanta, probably due to higher mining activity. The geo-accumulation index of the outdoor dust ranged from unpolluted to extremely polluted while that of the indoor dust ranged from moderately polluted to extremely polluted. Health risk assessments suggested that there was no potential non-carcinogenic health effect for Hg exposure relating to the dust to residents living in rooms of miners and non-miners.

Current status of advancement in remediation technologies for the toxic metal mercury in the environment: A critical review

Currently, pollution due to heavy metals, in particular dissolved mercury, is a major concern for society and the environment. This work aims to evaluate the current scenario regarding the removal/elimination of mercury. Mercury removal through adsorption is mainly done through artificial resins and metallic-organic frameworks. In the case of the zinc organic framework, it was able to adsorb Hg2+, reaching an adsorption capacity of 802 mg g-1. As for the Hg(0) the coconut husk was found to have the lowest equilibrium time, 30 min, and the highest adsorption capacity of 956.2 mg g-1. Experimental reports and molecular simulation indicate that the adsorption of mercury and other chemical forms occurs due to electrostatic interactions, ion exchange, precipitation, complexation, chelation, and covalent bonds, according to the material nature. The reported thermodynamic results show that, in most cases, the mercury adsorption has an endothermic nature with enthalpy levels below 40 kJ mol-1. Thermal and chemical regeneration methods lead to a similar number of 5 cycles for different materials. The presence of other ions, in particular cadmium, lead, and copper, generates an antagonistic effect for mercury adsorption. Regarding the other current technologies, it was found that mercury removal is feasible through precipitation, phytoremediation, and marine microalgae; all these methods require constant chemicals or a slow rate of removal according to the conditions. Advanced oxidative processes have noteworthy removal of Hg(0); however, Fenton processes lead to mineralization, which leads to Fe2+ and Fe3+ in solution; sonochemical processes are impossible to scale up at the current technology level; and electrochemical processes consume more energy and require constant changes of the anode and cathode. Overall, it is possible to conclude that the adsorption process remains a more friendly, economical, and greener process in comparison with other processes.

Exploring the spatial variation of mercury in the Gulf of St. Lawrence using northern gannets as fish samplers

Mercury (Hg) is a ubiquitous and pervasive environmental contaminant with detrimental effects on wildlife, which originates from both natural and anthropogenic sources. Its distribution within ecosystems is influenced by various biogeochemical processes, making it crucial to elucidate the factors driving this variability. To explore these factors, we employed an innovative method to use northern gannets (Morus bassanus) as biological samplers of regurgitated fish in the Gulf of St. Lawrence. We assessed fish total Hg (THg) concentrations in relation to their geographical catch location as well as to pertinent biotic and anthropogenic factors. In small fish species, trophic position, calculated from compound-specific stable nitrogen isotopes in amino acids, emerged as the most influential predictor of THg concentrations. For large fish species, THg concentrations were best explained by δ13C, indicating higher concentrations in inshore habitats. No anthropogenic factors, such as pollution, shipping traffic, or coastal development, were significantly related to THg concentrations in fish. Moreover, previously published THg data in mussels sampled nearby were positively linked with THg concentrations in gannet prey, suggesting consistent mercury distribution across trophic levels in the Gulf of St. Lawrence. Our findings point to habitat-dependent variability in THg concentrations across multiple trophic levels. Our study could have many potential uses in the future, including the identification of vulnerability hotspots for fish populations and their predators, or assessing risk factors for seabirds themselves by using biologically relevant prey.

A carbon dots-MnO2 nanosheet-based turn-on pseudochemodosimeter as low-cost probe for selective detection of hazardous mercury ion contaminations in water

Mercury is a highly hazardous element due to its profound toxicity and wide abundance in the environment. Despite the availability of various fluorimetric detection tools for Hg2+, including organic fluorophores and aptasensors, they often suffer from shortcomings like the utilization of expensive chemicals and toxic organic solvents, multi-step synthesis, sometimes with poor selectivity and low sensitivity. Whereas, biomass-derived fluorophores, such as carbon dots (CDs), present themselves as cost-effective and environmentally benign alternatives that exhibit comparable efficacy. Herein, we report a reaction-driven sensing assembly based on CDs, MnO2 nanosheets, and hydroquinone monothiocarbonate (HQTC) for the detection of Hg2+ ions, which relies on the formation of a CDs-MnO2 FRET-conjugate, resulting in the quenching of the intrinsic fluorescence of CDs. In a pseudochemodosimetric approach, the thiophilic nature of mercury was utilized for in-situ generation of the reducing species, hydroquinone from HQTC, resulting in the reduction of MnO2 nanosheets, the release of fluorescent CDs back to the solution. The low limit of detection (LOD) was achieved as 2 ppb (0.01 μM). The probe worked efficiently in real water samples like sea, river with good recovery of spiked Hg2+ and in some Indian ayurvedic medicines as well. Furthermore, solid-phase detection with sodium alginate beads demonstrated the ability of this cost-effective sensing assembly for onsite detection of Hg2+ ions.

Field method for preservation of total mercury in waters, including those associated with artisanal scale gold mining

Analysis of mercury (Hg) in natural water samples has routinely been impractical in many environments, for example, artisanal and small-scale gold mines (ASGM), where difficult conditions make monitoring of harmful elements and chemicals used in the processes highly challenging. Current sampling methods require the use of hazardous or expensive materials, and so difficulties in sample collection and transport are elevated. To solve this problem, a solid-phase extraction-based method was developed for the sampling and preservation of dissolved Hg in natural water samples, particularly those found around ASGM sites. Recoveries of 85% ± 10% total Hg were obtained during 4 weeks of storage in refrigerated (4 °C, dark) and unrefrigerated (16 °C, dark) conditions, and from a representative river water spiked to 1 μg L-1 Hg2+, 94% ± 1% Hg recovery was obtained. Solid-phase extraction loading flow rates were tested at 2, 5, and 10 mL min-1 with no breakthrough of Hg, and sorbent stability showed no breakthrough of Hg up to 2 weeks after functionalisation. The method was deployed across five artisanal gold mines in Kakamega gold belt, Kenya, to assess Hg concentrations in mine shaft water, ore washing ponds, and river and stream water, including drinking water sources. In all waters, Hg concentrations were below the WHO guideline limit value of 6 μg L-1, but drinking water sources contained trace concentrations of up to 0.35 μg L-1 total Hg, which may result in negative health effects from long-term exposure. The SPE method developed and deployed here is a robust sampling method that can therefore be applied in future Hg monitoring, toxicology, and environmental work to provide improved data that is representative of total dissolved Hg in water samples.

Risks to Human Health from Mercury in Gold Mining in the Coastal Region of Ecuador

Artisanal and small-scale gold mining (ASGM) plays a crucial role in global gold production. However, the adoption of poor mining practices or the use of mercury (Hg) in gold recovery processes has generated serious environmental contamination events. The focus of this study is assessing the concentration of Hg in surface waters within the coastal region of Ecuador. The results are used to conduct a human health risk assessment applying deterministic and probabilistic methods, specifically targeting groups vulnerable to exposure in affected mining environments. Between April and June 2022, 54 water samples were collected from rivers and streams adjacent to mining areas to determine Hg levels. In the health risk assessment, exposure routes through water ingestion and dermal contact were considered for both adults and children, following the model structures outlined by the U.S. Environmental Protection Agency. The results indicate elevated Hg concentrations in two of the five provinces studied, El Oro and Esmeraldas, where at least 88% and 75% of the samples, respectively, exceeded the maximum permissible limit (MPL) set by Ecuadorian regulations for the preservation of aquatic life. Furthermore, in El Oro province, 28% of the samples exceeded the MPL established for drinking water quality. The high concentrations of Hg could be related to illegal mining activity that uses Hg for gold recovery. Regarding the human health risk assessment, risk values above the safe exposure limit were estimated. Children were identified as the most vulnerable receptor. Therefore, there is an urgent need to establish effective regulations that guarantee the protection of river users in potentially contaminated areas. Finally, it is important to continue investigating the contamination caused by human practices in the coastal region.

Legacy Mercury Re-emission and Subsurface Migration at Contaminated Sites Constrained by Hg Isotopes and Chemical Speciation

The re-emission and subsurface migration of legacy mercury (Hg) are not well understood due to limited knowledge of the driving processes. To investigate these processes at a decommissioned chlor-alkali plant, we used mercury stable isotopes and chemical speciation analysis. The isotopic composition of volatilized Hg(0) was lighter compared to the bulk total Hg (THg) pool in salt-sludge and adjacent surface soil with mean ε202HgHg(0)-THg values of -3.29 and -2.35‰, respectively. Hg(0) exhibited dichotomous directions (E199HgHg(0)-THg = 0.17 and -0.16‰) of mass-independent fractionation (MIF) depending on the substrate from which it was emitted. We suggest that the positive MIF enrichment during Hg(0) re-emission from salt-sludge was overall controlled by the photoreduction of Hg(II) primarily ligated by Cl- and/or the evaporation of liquid Hg(0). In contrast, O-bonded Hg(II) species were more important in the adjacent surface soils. The migration of Hg from salt-sludge to subsurface soil associated with selective Hg(II) partitioning and speciation transformation resulted in deep soils depleted in heavy isotopes (δ202Hg = -2.5‰) and slightly enriched in odd isotopes (Δ199Hg = 0.1‰). When tracing sources using Hg isotopes, it is important to exercise caution, particularly when dealing with mobilized Hg, as this fraction represents only a small portion of the sources.

Spatio-temporal trends of mercury levels in alluvial gold mining spoils areas monitored between rainy and dry seasons in the Peruvian Amazon

Artisanal and small-scale gold mining (ASGM) in the Amazon has degraded tropical forests and escalated mercury (Hg) pollution, affecting biodiversity, ecological processes and rural livelihoods. In the Peruvian Amazon, ASGM annually releases some 181 tons of Hg into the environment. Despite some recent advances in understanding the spatial distribution of Hg within gold mine spoils and the surrounding landscape, temporal dynamics in Hg movement are not well understood. We aimed to reveal spatio-temporal trends of soil Hg in areas degraded by ASGM.,. We analyzed soil and sediment samples during the dry and rainy seasons across 14 ha of potentially contaminated sites and natural forests, in the vicinities of the Native community of San Jacinto in Madre de Dios, Peru. Soil Hg levels of areas impacted by ASGM (0.02 ± 0.02 mg kg-1) were generally below soil environmental quality standards (6.60 mg kg-1). However, they showed high variability, mainly explained by the type of natural cover vegetation, soil organic matter (SOM), clay and sand particles. Temporal trends in Hg levels in soils between seasons differed between landscape units distinguished in the mine spoils. During the rainy season, Hg levels decreased up to 45.5% in uncovered soils, while in artificial pond sediments Hg increased by up to 961%. During the dry season, uncovered degraded soils were more prone to lose Hg than sites covered by vegetation, mainly due to higher soil temperatures and concomitantly increasing volatilization. Soils from natural forests and degraded soil covered by regenerating vegetation showed a high capacity to retain Hg mainly due to the higher plant biomass, higher SOM, and increasing concentrations of clay particles. Disturbingly, our findings suggest high Hg mobility from gold mine spoil to close by sedimentary materials, mainly in artificial ponds through alluvial deposition and pluvial lixiviation. Thus, further research is needed on monitoring, and remediation of sediments in artificial to design sustainable land use strategies.

Serum levels of inflammatory cytokines in mercury mining workers in a precarious situation: A preliminary study

Mercury is a ubiquitous environmental xenobiotic; the primary sources of exposure to this metal are artisanal gold mining and the direct production of mercury. In Mexico, artisanal mercury mining continues to be an important activity in different regions of the country. Exposure to mercury vapors releases can have severe health impacts, including immunotoxic effects such as alterations in cytokine profiling. Therefore, in the present work, we evaluated the inflammatory cytokines profile in the blood serum of miners exposed to mercury. A cross-sectional observational study was performed on 27 mining workers (exposed group) and 20 control subjects (nonexposed group) from central Mexico. The mercury urine concentration (U-Hg) was determined by atomic absorption spectrometry, and IL-2, IL-6, IL-8, IL-10, and TNF-α were measured using a Multiplex Assay. The results showed that the U-Hg in the miners had a median value of 552.70 μg/g creatinine. All cytokines showed a significant increase in the miner group compared with the control group, except for TNF-α. In addition, we observed a positive correlation between U-Hg concentration and cytokine levels. In conclusion, mercury exposure correlated with cytokine levels (considered acute inflammatory marker) in miners; therefore, workers exposed to this metal show an acute systemic inflammation that could lead to alterations in other organs and systems.

The predictive machine learning model of a hydrated inverse vulcanized copolymer for effective mercury sequestration from wastewater

Inverse vulcanized polysulfides (IVP) are promising sulfur-enriched copolymers with unconventional properties irresistible for diverse applications like Hg2+ remediation. Nevertheless, due to their inherent hydrophobic nature, these copolymers still offer low Hg2+ uptake capacity. Herein, we reported the synthesis of IVP by reacting molten sulfur with 4-vinyl benzyl chloride, followed by their functionalization using N-methyl D-glucamine (NMDG) to increase the hydration of the developed IVP. The chemical composition and structure of the functionalized IVP were proposed based on FTIR and XPS analysis. The functionalized IVP demonstrated a high mercury adsorption capacity of 608 mg/g (compared to <26 mg/g for common IVP) because of rich sulfur and hydrophilic regions. NMDG functionalized IVP removed 100 % Hg2+ from a low feed concentration (10-50 mg/l). A predictive machine learning model was also developed to predict the amount of mercury removed (%) using GPR, ANN, Decision Tree, and SVM algorithms. Hyperparameter and loss function optimization was also carried out to reduce the prediction error. The optimized GPR algorithm demonstrated high R2 (0.99 (training) and 0.98 (unseen)) and low RMSE (2.74 (training) and 2.53 (unseen)) values indicating its goodness in predicting the amount of mercury removed. The produced functionalized IVP can be regenerated and reused with constant Hg2+ uptake capacity. Sulfur is the waste of the petrochemical industry and is abundantly available, making the functionalized IVP a sustainable and cheap adsorbent that can be produced for high-volume Hg2+ remediation. ENVIRONMENTAL IMPLICATION: This research effectively addresses the removal of the global top-priority neurotoxic pollutant mercury, which is toxic even at low concentrations. We attempted to remove the Hg2+ utilizing an inexpensive adsorbent developed by NMDG functionalized copolymer of molten sulfur and VBC. A predictive machine learning model was also formulated to predict the amount of mercury removal from wastewater with only a 0.05 % error which shows the goodness of the developed model. This work is critical in utilizing this low-cost adsorbent and demonstrates its potential for large-scale industrial application.

Assessment of land use and land cover, water nutrient and metal concentration related to illegal mining activities in an Austral semi-arid river system: A remote sensing and multivariate analysis approach

The mining sector in various countries, particularly in the sub-Saharan African region, faces significant impact from the emergence of small-scale unlicensed artisanal mines. This trend is influenced by the rising demand and prices for minerals, along with prevalent poverty levels. Thus, the detrimental impacts of these artisanal mines on the natural environment (i.e., rivers) have remained poorly understood particularly in the Zimbabwean context. To understand the consequences of this situation, a study was conducted in the Umzingwane Catchment, located in southern Zimbabwe, focusing on the variations in water nutrient and metal concentrations in rivers affected by illegal mining activities along their riparian zones. Using multi-year Sentinel-2 composite data and the random forest machine learning algorithm on the Google Earth Engine cloud-computing platform, we mapped the spatial distribution of illegal mines in the affected regions and seven distinct land use classes, including artisanal mines, bare surfaces, settlements, official mines, croplands, and natural vegetation, with an acceptable overall and class accuracies of ±70 % were identified. Artisanal mines were found to be located along rivers and this was attributed to their large water requirements needed during the mining process. The water quality analysis revealed elevated nutrient concentrations, such as ammonium and nitrate (range 0.10-20.0 mg L-1), which could be attributed to mine drainage from the use of ammonium nitrate explosives during mining activities. Additionally, the prevalence of croplands in the area may have potentially contributed to increased nutrient concentrations. The principal component analysis and hierarchical cluster analysis revealed three clusters, with one of these clusters showing parameters like Ca, Mg, K, Hg and Na, which are usually associated with mineral gypsum found in the drainage of artisanal mines in the selected rivers. Cluster 2 consisted of B, Cu, Fe, Pb, and Mn, which are likely from the natural environment and finally, cluster 3 contained As, Cd, Cr, and Zn, which were likely associated with both legal and illegal mining operations. These findings provide essential insights into the health of the studied river system and the impacts of human activities in the region. They further serve as a foundation for developing and implementing regulatory measures aimed at protecting riverine systems, in line with sustainable development goal 15.1 which focuses on preserving and conserving terrestrial and inland freshwater ecosystems, including rivers. By acting on this information, authorities can work towards safeguarding these vital natural resources and promoting sustainable development in the area.

Compound-specific stable nitrogen isotope analysis of amino acids shows that bulk methods provide higher estimates of mercury biomagnification in the Gulf of St. Lawrence

Compound-specific stable isotope analysis of amino acids (CSIA-AA) provides a method to estimate baseline δ15N values of food chains, allowing less biased estimates of trophic positions for organisms. Greater accuracy in trophic positions can improve estimates of contaminant biomagnification. We calculated trophic positions with various CSIA-AA equations for four species of fish and northern gannets (Morus bassanus) from the Gulf of St. Lawrence. We examined the effect of CSIA-AA-derived trophic positions on mercury biomagnification metrics (trophic magnification factors (TMF) and biomagnification factors) and compared these with trophic position estimates and metrics obtained from traditional bulk stable isotope analysis. The TMFs for the CSIA-AA equations ranged from 10 to 19, and bulk stable isotope analysis produced TMFs of 43, one of the highest TMFs recorded yet in the literature. Biomagnification factors between prey and northern gannets ranged from 20 to 42 using dietary observations and stable isotope mixing models. Our study demonstrates that discrepancies in biomagnification assessed using different approaches may go undetected when using a single approach.

An Unusual Cause of Complete Heart Block

Mercury poisoning is most frequently associated with multiorgan toxicity involving the brain, lungs, and kidneys. Cardiotoxic effects of mercury are rare and often overlooked. We demonstrate mercury poisoning-induced cardiotoxicity through a case study and then provide a review of the incidence, pathophysiology, and associated management plans. This case illustrates the importance of thorough history-taking to promote early recognition of toxicity.

Mercury speciation in selenium enriched wheat plants hydroponically exposed to mercury pollution

Mercury (Hg) pollution in agricultural soils and its potential pathway to the human food chain can pose a serious health concern. Understanding the pathway of Hg in plants and how the speciation may change upon interaction with other elements used for biofortification can be critical to assess the real implications for the final plant-based product. In that respect, selenium (Se) biofortification of crops grown in Se-poor soil regions is becoming a common practice to overcome Se deficient diets. Therefore, it is important to assess the interplay between these two elements since Se may form complexes with Hg reducing its bioavailability and toxicity. In this work, the speciation of Hg in wheat plants grown hydroponically under the presence of Hg (HgCl2) and biofortified with Se (selenite, selenate, or a 1:1 mixture of both) has been investigated by X-ray absorption spectroscopy at the Hg L3-edge. The main Hg species found in wheat grains was the highly toxic methylmercury. It was found that the Se-biofortification of wheat did not prevent, in general, the Hg translocation to grains. Only the 1:1 mixture treatment seemed to have an effect in reducing the levels of Hg and the presence of methylmercury in grains.

Transitional dynamics from mercury to cyanide-based processing in artisanal and small-scale gold mining: Social, economic, geochemical, and environmental considerations

Artisanal and small-scale gold mining (ASGM) is the leading global source of anthropogenic mercury (Hg) release to the environment. Top-down mercury reduction efforts have had limited results, but a bottom-up embrace of cyanide (CN) processing could eventually displace mercury amalgamation for gold recovery. However, ASGM transitions to cyanidation nearly always include an overlap phase, with mercury amalgamation then cyanidation being used sequentially. This paper uses a transdisciplinary approach that combines natural and social sciences to develop a holistic picture of why mercury and cyanide converge in gold processing and potential impacts that may be worse than either practice in isolation. We show that socio-economic factors drive the comingling of mercury and cyanide practices in ASGM as much or more so than technical factors. The resultant Hg-CN complexes have been implicated in increasing the mobility of mercury, compared to elemental mercury used in Hg-only processing. To support future inquiry, we identify key knowledge gaps including the role of Hg-CN complexes in mercury oxidation, transport, and fate, and possible links to mercury methylation. The global extent and increase of mercury and cyanide processing in ASGM underscores the importance of further research. The immediacy of the problem also demands interim policy responses while research advances, though ultimately, the well-documented struggles of mercury reduction efforts in ASGM temper optimism about policy responses to the mercury-cyanide transition.

A systematic review on metal contamination due to mining activities in the Amazon basin and associated environmental hazards

Metal contamination associated with mining activities has been considered one of the main environmental pollution problems in the Amazon region. Understanding the levels of metal contamination from mining activities requires a good understanding of background metal concentrations, which may vary notably according to the geology/lithology characteristics of the region, soil type, and predominant biogeochemical processes. This review assessed 50 papers and reports published between 1989 and 2020 describing environmental concentrations of different metals and metalloids (As, Hg, Mn, Fe, Cd, Cu, Cr, Pb, Ni, and Zn) in water and sediments of mining and non-mining areas in five geographic regions of the Amazon basin. Metal enrichment caused by mining activities was calculated and exposure concentrations were compared with sediment and water quality standards set for the protection of aquatic life. Significant enrichments of Cd, Cu, Cr, Fe, Hg, Mn, Ni and Zn were observed in mining areas in both sediment and water. Regarding background levels in the different geographic regions, the highest prevalence of metal enrichment (i.e., concentrations 10 to 100-fold higher than mean background values) in sediment samples was found for Fe (100% of samples), Ni (90%), and Mn (69%). For water, high prevalence of metal enrichment occurred for Zn, Mn, and Fe (100% of samples), and for Hg (86%). Hg, Fe, Pb, Cu, Cd, Ni and Zn exceeded water and/or sediment quality standards in a significant number of samples in the proximity of mining areas. This study indicates that mining activities significantly contribute to water and sediment contamination across the Amazon basin, posing hazards for freshwater ecosystems and potentially having human health implications.

Bacterial Metal-Scavengers Newly Isolated from Indonesian Gold Mine-Impacted Area: Bacillus altitudinis MIM12 as Novel Tools for Bio-Transformation of Mercury

Selikat river, located in the north part of Bengkulu Province, Indonesia, has critical environmental and ecological issues of contamination by mercury due to artisanal small-scale gold mining (ASGM) activities. The present study focused on the identification and bioremediation efficiency of the mercury-resistant bacteria (MRB) isolated from ASGM-impacted areas in Lebong Tambang village, Bengkulu Province, and analyzed their merA gene function in transforming Hg2+ to Hg0. Thirty-four MRB isolates were isolated, and four out of the 34 isolates exhibited not only the highest degree of resistance to Hg (up to 200 ppm) but also to cadmium (Cd), chromium (Cr), copper (Cu), and lead (Pb). Further analysis shows that all four selected isolates harbor a merA operon-encoded mercuric ion (Hg2+) reductase enzyme, with the Hg bioremediation efficiency varying from 71.60 to 91.30%. Additionally, the bioremediation efficiency for Cd, Cr, Cu, and Pb ranged from 54.36 to 98.37%. Among the 34, two isolates identified as Bacillus altitudinis possess effective and superior multi-metal degrading capacity up to 91.30% for Hg, 98.07% for Cu, and 54.36% for Cr. A pilot-scale study exhibited significant in situ bioremediation of Hg from gold mine tailings of 82.10 and 95.16% at 4- and 8-day intervals, respectively. Interestingly, translated nucleotide blast against bacteria and Bacilli merA sequence databases suggested that B. altitudinis harbor merA gene is the first case among Bacilli with the possibility exhibits a novel mechanism of bioremediation, considering our new finding. This study is the first to report the structural and functional Hg-resistant bacterial diversity of unexplored ASGM-impacted areas, emphasizing their biotechnological potential as novel tools for the biological transformation and adsorption of mercury and other toxic metals.

Assessment of Hg pollution in stream waters and human health risk in areas impacted by mining activities in the Ecuadorian Amazon

Illegal gold mining activities have contributed to the release and mobilization of Hg and environmental degradation in many parts of the world. This study aims to determine the concentration of Hg in five provinces of the Amazon Region of Ecuador, in addition to assessing the risk to human health of exposed populations, applying deterministic and probabilistic methods. For this purpose, 147 water samples were collected in rivers and streams crossing and/or located near mining areas. As a result, 100% of the samples analyzed exceeded the maximum permissible limit (MPL) according to the water quality criteria for the preservation of aquatic life of the Ecuadorian regulations, while 7% of the samples exceeded the MPL for drinking water. On the other hand, considering the European Environmental Quality Standard (EQS) for surface water bodies, in our study, 100% of the samples exceed the maximum permissible limit (0.07 µg/L), and with respect to the Canadian water quality guidelines, 35% of the samples exceed the permissible limit (0.001 mg/l) for drinking water, and 100% of the samples exceed the limit for life in water bodies (0.0001 mg/l). The risk assessment revealed that the probability of developing adverse health effects from exposure to Hg is below the recommended limits according to the probabilistic assessment; this is in relation to the criterion of residential and recreational use of water resources. However, it was identified that the child population doubles the acceptable systemic risk level according to the results of the deterministic assessment in the residential scenario. This information can be used by decision-makers to implement strategies to reduce Hg contamination and exposure of the population in Ecuadorian Amazonian rivers.

Towards a green mining future: A dynamic evolutionary game model for collaborative waste recycling

In the realm of environmental concerns, the management of mining waste has consistently emerged as a prominent issue. The accumulation of such waste not only results in substantial pollution but also signifies an inefficient use of resources. Rich in heavy metals and an array of toxic substances, mining waste poses a considerable challenge. In China, the situation is exacerbated by mining companies' inadequate and untimely efforts to address the extensive buildup of waste material. The long-term policy of recycling and regulating mining waste can be seen as the result of a long-term game between the government's regulatory decisions and the enterprises' fulfillment of their responsibilities, and the public's ability to participate in monitoring the decisions also changes the pattern of the game. In this study, we develop a tripartite evolutionary game model involving mining enterprises, the public, and local government. System dynamics are used to simulate the dynamic evolution of each stakeholder's strategy, examining the influence of various parameters on the evolution trajectory. Our findings show that: (1) reducing public subsidies, along with increasing enterprise supervision and penalties, effectively encourages public involvement in oversight and promotes proactive waste recycling by enterprises; (2) as enterprises actively engage in recycling efforts, the resulting environmental benefits boost public enthusiasm for participation in monitoring; (3) over time, heightened environmental awareness among the public and advances in recycling technology allow enterprises to improve the profitability of recycling, fostering a sustainable mine waste recycling industry; (4) once a virtuous mine waste recycling industry is established, enterprises autonomously engage in waste recycling, and the public actively participates in supervision, making strict government oversight unnecessary.

Rational design of selective functionalized silica adsorbents for Hg(II) removal from FGD wastewater. A combined experimental and theoretical study

The binding of Hg2+ by mercaptan-functionalized silica possessing different physical characteristics was explored through experimental investigations and theoretical calculations. The impacts of the pore structure of silica adsorbents on functionalization and the kinetics of Hg2+ adsorption were also studied. The mechanism of Hg2+ adsorption was proposed based on the results of experimental and theoretical studies. The DFT calculations suggested a simultaneous monodentate and bidentate Hg2+ complex formation on sulfur-containing surface functional groups that strongly depends on the Hg2+ concentration. Theoretical Hg2+ adsorption isotherms predicted by DFT calculations have shown that even when the adsorbent surface had heterogeneous adsorption sites capable of simultaneous monodentate and bidentate complexation, the adsorption still followed the Langmuir model.

Change in Values of Illegal Miners and Inhabitants and Reduction in Environmental Pollution after the Cessation of Artisanal and Small-Scale Gold Mining: A Case of Bunikasih, Indonesia

Artisanal and small-scale gold mining (ASGM) harms the environment and human health, because it requires mercury (Hg). Therefore, this study uses a questionnaire survey to identify the effects of the medical checkup findings, group discussion, and educational seminar on the values of illegal miners and residents in Bunikasih, Indonesia, regarding the environmental and health effects of Hg. Transdisciplinary communities of practice (TDCoP) were formed to pursue alternative livelihoods than illegal ASGM. Environmental pollution after ASGM closure was assessed. The questionnaire showed that respondents changed their views on Hg's effects and were willing to stop ASGM practices. In an environmental impact assessment study, tea leaf samples were obtained between the ASGM activity location and village housing in two periods during ASGM closure to identify the concentrations of Hg, lead, and arsenic. Their mean concentration values in Period 1 (2) were 0.54 ± 0.14, 0.66 ± 0.09, and 0.34 ± 0.12 mg kg-1 (0.08 ± 0.04, 0.34 ± 0.14, and 0.07 ± 0.06 mg kg-1), respectively, indicating a decrease in environmental pollution. In conclusion, the government-driven cessation of ASGM in the study area shows a reduction in environmental pollution, and the change in the perception of the participants regarding the ASGM and TDCoP approaches help to make these changes permanent.

Rural Knowledge Transformation in Terms of Mercury Used in Artisanal Small-Scale Gold Mining (ASGM)-A Case Study in Gorontalo, Indonesia

Gorontalo is reputed to be one of the best-quality gold producers in the Indonesian archipelago. Gold production has been largely achieved through the activities of artisanal small-scale gold mining (ASGM), which as part of its extraction process, primarily uses mercury-a substance known to cause negative impacts on health and the environment, leading also to numerous socio-economic issues. This research aims (1) to investigate the extent of rural knowledge regarding mercury and to determine whether a video that explains mercury and the problems that occur as a result of ASGM can significantly transform rural populations' knowledge; (2) to inspect different factors separating the SR group (those who live in the same regency as the ASGM area) from the NR group (those who live in the neighboring regency/city of the ASGM area) and to find out whether said factors are statistically significant. The results show that the test subjects' knowledge of mercury had increased after watching the video, and that their willingness to oppose ASGM activities is one of the significant factors within the two groups. Moreover, this paper briefly describes the follow-up activities of the SRIREP project (Co-creation of Sustainable Regional Innovation for Reducing Risk of High-impact Environmental Pollution) in encouraging rural communities to explore sustainable livelihoods as an alternative to ASGM.

Fusion-Assisted Hydrothermal Synthesis of Technogenic-Waste-Derived Zeolites and Nanocomposites: Synthesis, Characterization, and Mercury (II) Adsorption

This study presents the synthesis of zeolites derived from coal fly ash (CFA) using the fusion-assisted alkaline hydrothermal method. The zeolites were synthesized by combining CFA and NaOH at a molar ratio of 1:1.2 under fusion temperatures of 500, 600, and 700 °C. Subsequently, the obtained zeolites were subjected to further modifications through the incorporation of magnetic (Fe₃O₄) and silver (Ag⁰) nanoparticles (NPs). The Fe₃O₄ NPs were introduced through co-precipitation of Fe(NO₃)₂ and FeCl₃ at a molar ratio of 1:1, followed by thermal curing at 120 °C. On the other hand, the Ag⁰ NPs were incorporated via ion exchange of Na⁺ with Ag⁺ and subsequent reduction using NaBH₄. The synthesized porous materials exhibited the formation of zeolites, specifically analcime and sodalite, as confirmed by X-ray diffraction (XRD) analysis. Additionally, the presence of Fe₃O₄ and Ag⁰ NPs was also confirmed by XRD analysis. The elemental composition analysis of the synthesized nanocomposites further validated the successful formation of Fe₃O₄ and Ag⁰ NPs. Nitrogen porosimetric analysis revealed the formation of a microporous structure, with the BET surface area of the zeolites and nanocomposites ranging from 48.6 to 128.7 m²/g and pore sizes ranging from 0.6 to 4.8 nm. The porosimetric characteristics of the zeolites exhibited noticeable changes after the modification process, which can be attributed to the impregnation of Fe₃O₄ and Ag⁰ NPs. The findings of this research demonstrate the effectiveness of the fusion-assisted method in producing synthetic zeolites and nanocomposites derived from CFA. The resulting composites were evaluated for their potential application in the removal of mercury ions from aqueous solutions. Among the samples tested, the composite containing Ag⁰ NPs exhibited the highest adsorption capacity, reaching 107.4 mg of Hg²⁺ per gram of composite. The composites modified with Fe₃O₄ NPs and Ag/Fe₃O₄ nanocomposites displayed adsorption capacities of 68.4 mg/g and 71.4 mg/g, respectively.

Ecotoxicological impacts of metals in single and co-exposure on mussels: Comparison of observable and predicted results

Used in high-tech and everyday products, mercury (Hg), cobalt (Co), and nickel (Ni) are known to be persistent and potentially toxic elements that pose a serious threat to the most vulnerable ecosystems. Despite being on the Priority Hazardous Substances List, existing studies have only assessed the individual toxicity of Co, Ni and Hg in aquatic organisms, with a focus on the latter, ignoring potential synergistic effects that may occur in real-world contamination scenarios. The present study evaluated the responses of the mussel Mytilus galloprovincialis, recognized as a good bioindicator of pollution, after exposure to Hg (25 μg/L), Co (200 μg/L) and Ni (200 μg/L) individually, and to the mixture of the three metals at the same concentration. The exposure lasted 28 days at 17 ± 1 °C, after which metal accumulation and a set of biomarkers related to organisms' metabolic capacity and oxidative status were measured. The results showed that the mussels could accumulate metals in both single- and co-exposure conditions (bioconcentration factors between 115 and 808) and that exposure to metals induced the activation of antioxidant enzymes. Although Hg concentration in organisms in the mixture decreased significantly compared to single exposure (9.4 ± 0.8 vs 21 ± 0.7 mg/kg), the negative effects increased in the mixture of the three elements, resulting in depletion of energy reserves, activation of antioxidants and detoxification enzymes, and cellular damage, with a hormesis response pattern. This study underscores the importance of risk assessment studies that include the effects of the combination of pollutants and demonstrates the limitations of applying models to predict metal mixture toxicity, especially when a hormesis response is given by the organisms.

Electrochemical Synthesis of Poly(trisulfides)

With increasing interest in high sulfur content polymers, there is a need to develop new methods for their synthesis that feature improved safety and control of structure. In this report, electrochemically initiated ring-opening polymerization of norbornene-based cyclic trisulfide monomers delivered well-defined, linear poly(trisulfides), which were solution processable. Electrochemistry provided a controlled initiation step that obviates the need for hazardous chemical initiators. The high temperatures required for inverse vulcanization are also avoided resulting in an improved safety profile. Density functional theory calculations revealed a reversible "self-correcting" mechanism that ensures trisulfide linkages between monomer units. This control over sulfur rank is a new benchmark for high sulfur content polymers and creates opportunities to better understand the effects of sulfur rank on polymer properties. Thermogravimetric analysis coupled with mass spectrometry revealed the ability to recycle the polymer to the cyclic trisulfide monomer by thermal depolymerization. The featured poly(trisulfide) is an effective gold sorbent, with potential applications in mining and electronic waste recycling. A water-soluble poly(trisulfide) containing a carboxylic acid group was also produced and found to be effective in the binding and recovery of copper from aqueous media.

Environmental contamination and health risk assessment of potentially toxic trace metal elements in soils near gold mines - A global meta-analysis

Gold mining is the most important anthropogenic source of heavy metal emissions into the environment. Researchers have been aware of the environmental impacts of gold mining activities and have conducted studies in recent years, but they have only selected one gold mining site and collected soil samples in its vicinity for analysis, which does not reflect the combined impact of all gold mining activities on the concentration of potentially toxic trace elements (PTES) in nearby soils at a global scale. In this study, 77 research papers from 24 countries were collected from 2001 to 2022, and a new dataset was developed to provide a comprehensive study of the distribution characteristics, contamination characteristics, and risk assessment of 10 PTEs (As, Cd, Cr, Co, Cu, Hg, Mn, Ni, Pb, and Zn) in soils near the deposits. The results show that the average levels of all 10 elements are higher than the global background values and are at different levels of contamination, with As, Cd, and Hg at strong contamination levels and serious ecological risks. As and Hg contribute to a greater non-carcinogenic risk to both children and adults in the vicinity of the gold mine, and the carcinogenic risks of As, Cd, and Cu are beyond the acceptable range. Gold mining on a global scale has already caused serious impacts on nearby soils and should be given adequate attention. Timely heavy metal treatment and landscape restoration of extracted gold mines and environmentally friendly approaches such as bio-mining of unexplored gold mines where adequate protection is available are of great significance.

Our evolved understanding of the human health risks of mercury

Mercury (Hg) is a chemical of health concern worldwide that is now being acted upon through the Minamata Convention. Operationalizing the Convention and tracking its effectiveness requires empathy of the diversity and variation of mercury exposure and risk in populations worldwide. As part of the health plenary for the 15th International Conference on Mercury as a Global Pollutant (ICMGP), this review paper details how scientific understandings have evolved over time, from tragic poisoning events in the mid-twentieth century to important epidemiological studies in the late-twentieth century in the Seychelles and Faroe Islands, the Arctic and Amazon. Entering the twenty-first century, studies on diverse source-exposure scenarios (e.g., ASGM, amalgams, contaminated sites, cosmetics, electronic waste) from across global regions have expanded understandings and exemplified the need to consider socio-environmental variables and local contexts when conducting health studies. We conclude with perspectives on next steps for mercury health research in the post-Minamata Convention era.

Mercury and artisanal and small-scale gold mining: Review of global use estimates and considerations for promoting mercury-free alternatives

Artisanal and small-scale gold mining (ASGM) is present in over 80 countries, employing about 15 million miners and serving as source of livelihood for millions more. The sector is estimated to be the largest emitter of mercury globally. The Minamata Convention on Mercury seeks to reduce and, where feasible, eliminate mercury use in the ASGM. However, the total quantity of mercury used in ASGM globally is still highly uncertain, and the adoption of mercury-free technologies has been limited. This paper presents an overview of new data, derived from Minamata ASGM National Action Plan submissions, that can contribute to refining estimates of mercury use in ASGM, and then assesses technologies that can support the phase out mercury use in ASGM while increasing gold recovery. The paper concludes with a discussion of social and economic barriers to adoption of these technologies, illustrated by a case study from Uganda.

Noise, Air, and Heavy Metal Pollution as Risk Factors for Endothelial Dysfunction

During the last two decades, large epidemiological studies have shown that the physical environment, including noise, air pollution or heavy metals, have a considerable impact on human health. It is known that the most common cardiovascular risk factors are all associated with endothelial dysfunction. Vascular tone, circulation of blood cells, inflammation, and platelet activity are some of the most essential functions regulated by the endothelium that suffer negative effects as a consequence of environmental pollution, causing endothelial dysfunction. In this review, we delineate the impact of environmental risk factors in connection to endothelial function. On a mechanistic level, a significant number of studies suggest the involvement of endothelial dysfunction to fundamentally drive the adverse endothelium health effects of the different pollutants. We focus on well-established studies that demonstrate the negative effects on the endothelium, with a focus on air, noise, and heavy metal pollution. This in-depth review on endothelial dysfunction as a consequence of the physical environment aims to contribute to the associated research needs by evaluating current findings from human and animal studies. From a public health perspective, these findings may also help to reinforce efforts promoting the research for adequate promising biomarkers for cardiovascular diseases since endothelial function is considered a hallmark of environmental stressor health effects.

Emerging mercury and methylmercury contamination from new artisanal and small-scale gold mining along the Nile Valley, Egypt

The past decade witnessed the initiation and boom of the Artisanal and Small-scale Gold Mining (ASGM) activities in the hyper-arid southern Egypt. The ores are mined in the Eastern Desert and then transported to the densely populated farming communities in the Nile Valley, where the river provides the water resources needed for ore processing. In search for economic benefits, the poorly educated farmers with limited technical resources transformed their cultivated lands into ASGM operations, exposing themselves, their families, the residents, and the Nile ecosystems to several environmental and occupational health problems. Using integrated remote sensing, field, geochemical, and isotopic analyses, we report the first inventory of ASGM-related total mercury (THg) and methylmercury (MeHg) levels in tailings, amalgamation-tailing ponds, and surface and groundwater with emphasis on the Edfu city and its surroundings. The field and remote sensing-based mapping of ASGM activities reveals clustering around the Nile waterways and suggests interaction of Hg contamination sources with their surrounding receptors. Common ASGM practices include release of contaminated water from unlined amalgamation-tailing ponds into irrigation and drainage canals, and spreading of tailings over cultivated soils. In a short period (10 years), the released Hg contaminated multiple media, including the surface water, the shallow and deep aquifers, and possibly the soil, crops, and livestock. THg levels in amalgamation-tailing ponds (1200-8470 ng/L) are fourfold higher than US EPA and eightfold the WHO thresholds. The contaminated waters released from amalgamation-tailing ponds raised THg levels in surface water (irrigation canals: 50-100 ng/L; drainage canals: THg: > 200 ng/L) and groundwater (shallow and deep aquifers: 80-500 ng/L). Our findings highlight the need to extend the adopted approach to cover the entire length of the Nile River and its valley and the importance of conducting awareness campaigns to educate residents and health care providers about potential ASGM-related environmental and health hazards.

Application of response surface methodology and box-behnken design for the optimization of mercury removal by Ulva sp

Mercury (Hg) is a global and top priority contaminant, toxic at low concentrations. Although it has been progressively eliminated from processes, this metal continues to circulate in the atmosphere, soil, and water. In this work, the Response Surface Methodology (RSM) combined with a Box-Behnken Design (3 factors - 3 levels) was used to optimize key operational conditions that influence the removal and uptake of Hg by living macroalga Ulva sp. in a complex mixture containing several elements used in industry (potentially toxic elements, rare earth elements, and platinum-group elements) (initial concentration 10, 100 and 190 µg/L, salinity 15, 25 and 35, seaweed stock density 1.0, 3.0 and 5.0 g/L). Results evidenced the great capability of Ulva sp. to remove Hg, with removal efficiencies between 69 % and 97 %. 3-D surfaces showed that the most impactful variable was seaweed stock density, with higher densities leading to higher removal. Regarding the uptake, a positive correlation between initial concentration and q_t values was observed. The appliance of RSM made possible to obtain optimal operating conditions for removing virtually 100 % of Hg from waters with high ionic strength, which is a pivotal step in the direction of the application of this remediation biotechnology at large scale.

Metal(loid)-specific sources and distribution mechanisms of riverside soil contamination near an abandoned gold mine in Mongolia

Tailings were discharged to the Boroo River from gold mining by amalgamation, resulting in soil contamination near the river. To identify the sources and distribution mechanisms of each metal(loid) in the soil, a total of 184 soil samples were collected near the river and analyzed for As, Cd, Cu, Pb, Zn, and Hg contents. According to the positive matrix factorization result, three factors affected the contamination levels: the application of Hg for gold mining (Factor 1), light minerals containing Cu and Zn (Factor 2), and heavy minerals containing As and Cd (Factor 3). Soil samples were classified into four groups by hierarchical clustering. Groups A and B seemed to be affected by light and heavy minerals discharged in early and later stages of ore processing, respectively. The spatial distribution of the groups suggested differentiation in travel distances by specific gravity. Groups C and D showed high Hg contents implying the effect of Hg mismanagement and spill accidents. The study results show that the distribution of soil contaminants near rivers in mining areas is controlled by the specific gravity of minerals discharged to the environment (e.g., river), ore processing stages, and insufficient recovery and/or spills of Hg, which will help establish restoration measures.

Competitive fiber optic sensors for the highly selective detection of mercury in water

Two competitive fiber optic sensors for the rapid, sensitive, and highly selective detection of mercury in water are designed, fabricated, and evaluated. A wavelength-modulated sensor based on an etched single-mode-multimode-single-mode (E-SMS) optical fiber structure and an intensity-modulated sensor based on fiber optics with a slanted end were fabricated by readily reproducible methods. The sensors were activated with a nanostructured chitosan/maghemite (CS/Fe₂O₃) composite thin film for the selective detection of mercury ions (Hg²⁺) in water. The functionalized sensors were implemented to experimentally validate the potential of CS/Fe₂O₃ thin film for optical sensing of Hg²⁺ in drinking water. The sensor based on the E-SMS structure exhibited a wavelength-modulated response with a sensitivity of up to 290 pm/(µg/mL), and the sensor based on the slanted end structure showed an intensity-modulated response with a sensitivity of -0.07dBm/(µg/mL). Validation of the experimental assay method proves the ability to selectively detect chemical interactions as low as 1 ng/mL (one part per billion) of Hg²⁺ in water for both sensors. The high specificity of the two sensors was demonstrated by evaluating their responses to a number of potentially interfering metal ions in water. These sensors are cost-effective, simple to construct, and easy to implement, which makes them very promising for the on-site detection and monitoring of mercury in bodies of water.

Participative epidemiology and prevention pathway of health risks associated with artisanal mines in Luhihi area, DR Congo

BACKGROUND

Health issues are associated with artisanal mining in the DR Congo. The scenario is worst when artisanal mining is done informally or with limited material and technical resources. This paper argues that the adoption of healthy practices by artisanal miners might be limited given that it involves unrealistic socio-economic, and administrative aspects and access to health risk prevention means. Making a conceptual framework on the feasibility of revolutionizing artisanal mining practices linked to health risks in the DR Congo requires trans-disciplinary interventions and researches. This case study aims at co-analyzing with actors in the Luhihi artisanal gold mine, the epidemiology of health issues. It also aims at describing the dynamics of resources that mining actors mobilize or think they can mobilize in order to prevent health risks.

METHODS

A "socio-anthropological" qualitative study with "transdisciplinary methods" was carried out the Luhihi artisanal mining. Data collection tools and methods included an exploratory survey, semi-structured interviews. Focus groups (FG) mixed with proportional piling were used to support the open-ended interview discussions. The actors interviewed were selected by "convenience sampling" and the saturation principle indicated the size of the sampling. In total, 67 persons were interviewed and 5 FG each consisting of 5 to 10 mining actors were organized. Data were triangulated among respondents to ensure their veracity and an "inductive thematic data analysis" was applied.

RESULTS

Key findings are the role of actors involved the organization system at the Luhihi artisanal mining site; a description of a participative epidemiology and determinants of health issues; presentation of the importance of health risks as perceived by mining actors; the constraints in the common illenesses treatment; and opportunities of collective actions for gathering resources required for the organization of healthcare services.

CONCLUSION

The results are translated into a grid of powers and interests in relation to the mobilization of resources for the prevention and treatment of health issues. The dialogue for change regarding the ignorance of the actors to exposure to chemical risks such as to exposure mercury, silica, carbon monoxide, and cyanide also entailed the translation of the results. In addition, an analysis of the ability of artisanal mining actors to implement health risk prevention services was made.

Nonfatal Occupational Injuries Among Artisanal and Small-scale Gold Mining Workers in Ethiopia

Background

Artisanal and Small-scale Gold Mining (ASGM) is widely practiced in Ethiopia. Injuries are among the public health concerns in the mining sector. This study aimed to assess the prevalence of nonfatal occupational injuries and associated factors among workers in ASGM in Ethiopia.

Methods

A cross-sectional study design was employed from April to June 2020. A total of 403 participants were selected with a simple random sampling technique. A structured questionnaire was utilized for the data collection. Descriptive statistics were used to characterize the information and binary logistic regression was applied to test the association. Predictor variables with P-value < .05 with an Odds ratio of 95% CI in multivariable analysis were considered as associated factors.

Results

A total of 403 participants were interviewed with a response rate of 95.5%. The prevalence of nonfatal occupational injury was 25.1% in the past 12 months. About one-third of the injuries, 32 (31.7%), were on the upper extremity and feet, 18 (17.8%). Symptoms of mercury toxicity (AOR: 2.39, 95% CI [1.27-4.52]), 1 to 4 years of work experience (AOR: 4.50, 95% CI [1.57-12.9]), full work shift (AOR: 6.06, 95% CI [1.97-18.7]), and job in the task of mining activities (AOR: 4.83, 95% CI [1.48-15.7]) were associated with the injury.

Conclusion

A substantially high prevalence of injuries was observed. Work-related factors were found to be significantly associated with the occurrence of injury. The government body, mining sector, and workers are advised to apply interventions focusing on the improvement of working conditions and safety practices to minimize injury.

Assessment of surface water quality and mercury levels from Artisanal and small-scale gold mining (ASGM) along Acupan River, Benguet, Philippines

Artisanal and small-scale mining activities are most evident among communities surrounding the Acupan River in Itogon Benguet. The mining activities include manual extraction of gold ores, use of improvised ball/rod mills and sluice boxes, and metallurgical processing such as cyanidation, carbon-in-pulp (CIP) and amalgamation. This study evaluates the influence of small-scale mining and the geology/mineralization of the Acupan Au-Ag-Te deposit to the water quality of the Acupan River and to the possible human exposures to Hg within the small-scale mining community. Different water quality parameters were monitored along selected sites along the Acupan River for a year and the results showed that the low average values of dissolve oxygen (DO) (2.54-4.53 mg L^-1) and the relatively high average values of pH (8.84-10.10), sulfate (300.00-1133.33 mg L^-1), nitrate (11.33-134.67 mg L^-1), arsenic (As) (0.227-0.574 mg L^-1) and mercury (Hg) (0.004-0.054 mg L^-1) have exceeded the acceptable criteria limit of the Department of Environment and Natural Resources for Class C waters. The exceeded values are noted to occur in areas where extensive small-scale mining activities are being done and have affected as well the downstream areas. To test possible human contamination in the use of Hg, hair samples from 56 volunteers were analyzed for total Hg (T-Hg) following standard protocols. The T-Hg concentrations in hair samples are mostly inorganic and are determined in various parameters such as sex, geographic location, occupation, age, fish consumption and localization in hair. Though not significantly different, higher Hg values are noted in males (1.280 ± 0.446 ng mg^-1) than among females (0.651 ± 0.163 ng mg^-1) as well as those with ages 41-50 years (3.130 ± 2.330 ng mg^-1) as compared to other age groups. The higher amounts of inorganic Hg in human hairs could be attributed to the discrete yet prevalent use of amalgamation. The findings of this study emphasize the need for better regulations of the small-scale mining activities and for stricter implementation of the total ban on the use of Hg in ore processing to ensure better water quality of Acupan River as well as the health and safety of the communities surrounding the river.

Roadmap to mercury-free dentistry era: Are we prepared?

From the perspectives of longevity, mechanical performance, and economics, amalgam has long been considered the material of choice, especially for certain types of restorations in posterior teeth, including replacement therapy for existing amalgam fillings. In spite of numerous advantages over other filling materials, its use has been decreasing in recent years and the alternative tooth-colored filling materials are increasingly used. There is a trend towards minimal interventional, adhesive, techniques in dentistry, which are based on adhesion to tooth structure by chemical interaction and/or micromechanical retention. At the same time, the quality and durability of alternative materials have improved. Mercury is the metallic element of concern used in dental amalgam. Mercury is a well-documented toxicant, with reasonably well-defined characteristics for the major forms of exposure, involving elemental mercury as well as organic and inorganic mercury compounds. Looking into the kind of practice and its popularity among dentists and the patients in India, even we have to comply with the use of amalgam by implementing the best possible ways to minimize the extent of damage to nature.

Effects of illegal gold mining on Hg concentrations in water, Pistia stratiotes, suspended particulate matter, and bottom sediments of two impacted rivers (Paraíba do Sul River and Muriaé River), Southeastern, Brazil

Recent reports of illegal small-scale alluvial gold mining activities (locally called garimpo) by miners working on rafts in the Paraíba do Sul River (PSR) and in one of its tributaries (Muriaé River (MR)) have raised concerns about Hg contamination. This study aimed to evaluate the impact of garimpo activities on Hg contamination in three environmental compartments. Water, sediment, and aquatic macrophytes (Pistia stratiotes) were sampled during the rainy season in PSR, forming a 106-km transect from the point where garimpo rafts were seen and/or seized by the Federal Police. They were also sampled in the MR. Total and dissolved mercury (Hg) concentrations in water and total Hg in the suspended particulate matter (SPM) sampled in the PSR increased by 1.7, 1.5, and 2.1 times at the points where the rafts were seen compared to the point immediately upstream. In the MR, Hg concentrations were higher than those in the PSR, but most values in the environmental compartments were below the safe limits (174-486 ng∙g^-1, threshold and probable effect level, respectively), with the exception of Hg in the SPM of one of the MR sampling points (256 ng∙g^-1) and the mining tailings (197 ng∙g^-1). Sediment granulometry was exponentially associated with Hg concentrations in the sediment (R² = 0.75, p < 0.0001) and is also essential to understand the physical impacts of garimpo on PSR. Future studies should focus on assessing the seasonal variability of Hg concentrations in the studied compartments, especially if garimpo is identified during the dry season.

Potential Health Effects of Heavy Metals and Carcinogenic Health Risk Estimation of Pb and Cd Contaminated Eggs from a Closed Gold Mine Area in Northern Thailand

Gold-mining activities have been demonstrated to result in significant environmental pollution by Hg, Pb, and Mn, causing serious concerns regarding the potential threat to the public health of neighboring populations around the world. The present study focused on heavy-metal contamination in the eggs, blood, feed, soil, and drinking water on chicken farms, duck farms, and free-grazing duck farms located in areas < 25 km and > 25 km away from a gold mine in northern Thailand. In an area < 25 km away, Hg, Pb, and Mn concentrations in the eggs of free-grazing ducks were significantly higher than > 25 km away (p < 0.05). In blood, Hg concentration in free-grazing ducks was also significantly higher than those in an area > 25 km away (p < 0.05). Furthermore, the Pb concentration in the blood of farm ducks was significantly higher than in an area > 25 km away (p < 0.05). The concentration of Cd in drinking water on chicken farms was significantly higher for farms located within 25 km of the gold mine (p < 0.05). Furthermore, a high correlation was shown between the Pb (r2 = 0.84) and Cd (r2 = 0.42) found between drinking water and blood in free-grazing ducks in the area < 25 km away. Therefore, health risk from heavy-metal contamination was inevitably avoided in free-grazing activity near the gold mine. The incremental lifetime cancer risk (ILCR) in the population of both Pb and Cd exceeded the cancer limit (10−4) for all age groups in both areas, which was particularly high in the area < 25 km for chicken-egg consumption, especially among people aged 13−18 and 18−35 years old. Based on these findings, long-term surveillance regarding human and animal health risk must be strictly operated through food chains and an appropriate control plan for poultry businesses roaming around the gold mine.

Reducing disease and death from Artisanal and Small-Scale Mining (ASM) - the urgent need for responsible mining in the context of growing global demand for minerals and metals for climate change mitigation

Artisanal and small-scale mining (ASM) takes place under extreme conditions with a lack of occupational health and safety. As the demand for metals is increasing due in part to their extensive use in 'green technologies' for climate change mitigation, the negative environmental and occupational consequences of mining practices are disproportionately felt in low- and middle-income countries. The Collegium Ramazzini statement on ASM presents updated information on its neglected health hazards that include multiple toxic hazards, most notably mercury, lead, cyanide, arsenic, cadmium, and cobalt, as well as physical hazards, most notably airborne dust and noise, and the high risk of infectious diseases. These hazards affect both miners and mining communities as working and living spaces are rarely separated. The impact on children and women is often severe, including hazardous exposures during the child-bearing age and pregnancies, and the risk of child labor. We suggest strategies for the mitigation of these hazards and classify those according to primordial, primary, secondary, and tertiary prevention. Further, we identify knowledge gaps and issue recommendations for international, national, and local governments, metal purchasers, and employers are given. With this statement, the Collegium Ramazzini calls for the extension of efforts to minimize all hazards that confront ASM miners and their families.

Mercury Phytotoxicity and Tolerance in Three Wild Plants during Germination and Seedling Development

By examining plant responses to heavy metal stress during the early stages of the life cycle, we can predict their tolerance and survival in polluted areas as well as their potential for bioremediation. The objective of our study was to evaluate the effect of exposure to mercury (Hg) on the germination and in vitro development of three plant species: Bidens pilosa, Taraxacum officinale (Asteraceae), and Heliocarpus americanus (Malvaceae). These are wild ecotypes adapted to local edaphoclimatic conditions in southern Ecuador, an area which has been historically affected by artisanal and small-scale gold mining (SSGM). For comparison, we additionally used a known Hg-tolerant plant, Lactuca sativa (Asteraceae). We tested biorelevant concentrations of Hg, equivalent to those occurring in soils affected by SSGM, i.e., up to 4.0 mg/L of Hg. The relative inhibitory effects of the treatments (0.6, 2.0, and 4.0 mg/L of Hg) on the germination percentage were most evident in T. officinale, followed by B. pilosa, while L. sativa and H. americanus were not affected. In terms of the time needed to reach 50% germination (T50), B. pilosa exposed to higher concentrations of Hg showed an increase in T50, while H. americanus showed a significant reduction compared to the control treatment. The reduction in radicle length at 4.0 mg/L Hg compared to the control was more evident in L. sativa (86%) than in B. pilosa (55.3%) and H. americanus (31.5%). We concluded that, in a scenario of Hg contamination in the evaluated concentration range, the grass B. pilosa and the tree H. americanus could have a higher probability of establishment and survival.

Novel Dynamic Technique, Nano-DIHM, for Rapid Detection of Oil, Heavy Metals, and Biological Spills in Aquatic Systems

Numerous anthropogenic and natural particle contaminants exist in diverse aquatic systems, with widely unknown environmental fates. We coupled a flow tube with a digital in-line holographic microscopy (nano-DIHM) technique for aquatic matrices, for in situ real-time analysis of particle size, shape, and phase. Nano-DIHM enables 4D tracking of particles in water and their transformations in three-dimensional space. We demonstrate that nano-DIHM can be automated to detect and track oil spills/oil droplets in dynamic systems. We provide evidence that nano-DIHM can detect the MS2 bacteriophage as a representative biological-viral material and mercury-containing particles alongside other heavy metals as common toxic contaminants. Nano-DIHM shows the capability of observation of combined materials in water, characterizing the interactions of various particles in mixtures, and particles with different coatings in a suspension. The observed sizes of the particles and droplets ranged from ∼1 to 200 μm. We herein demonstrate the ability of nano-DIHM to characterize and distinguish particle-based contaminants in water and their interactions in both stationary and dynamic modes with a 62.5 millisecond time resolution. The fully automated software for dynamic and real-time detection of contaminants will be of global significance. A comparison is also made between nano-DIHM and established techniques such as S/TEM for their different capabilities. Nano-DIHM can provide a range of physicochemical information in stationary and dynamic modes, allowing life cycle analysis of diverse particle contaminants in different aquatic systems, and serve as an effective tool for rapid response for spills and remediation of natural waters.

Mercury levels in North Atlantic seabirds: A synthesis

Mercury (Hg) is globally-distributed, with severe toxic effects on wildlife. Methylmercury biomagnifies within food webs, so long-lived, top predators such as seabirds are prone to high mercury concentrations. We synthesized historical and contemporary data on mercury concentrations in seabirds from the North Atlantic. We collected 614 values determined from 39 species and 115 locations, ranging from 1895 to 1940 and from 1970 to 2020. Highest blood-equivalent Hg values were in Phalacrocoracidae. For the same species/tissue/collection site, blood-equivalent values were lower during pre-1940 than post-1970 period. In almost 5 % of post-1970 values, mean blood-equivalent Hg concentrations were above those considered to pose severe risks of adverse effects, and 21 % were above the high-risk effect. We found an imbalance in sample effort and did not find Hg values for many species. We argue that stronger, trans-Atlantic Hg monitoring schemes are required to coordinate research and better compare trends across a wide scale.