Gold Mining Research Articles

Biomonitoring of exposure to metals and metalloids using toenail and fingernail sampling in individuals from artisanal gold mining areas in Mali

Artisanal gold mining can release metallic elements in the environment that can result in occupational and environmental exposures. This pilot study aimed to assess exposure to metals and metalloids from fingernail and toenail samples in artisanal gold mine workers, inhabitants of a mining and non-mining village in Mali. As it can be particularly challenging to collect and transport biological samples from remote areas, nail sample collection was tested as a potential choice for multielement biomonitoring. A convenience sampling of 315 individuals was performed equally distributed in each location group (105 per location) and stratified by populational group (male adults, female adults, and people <18 years). Toenail and fingernail samples were collected from each participant and twenty-one elements (aluminum (Al), arsenic (As), barium (Ba), beryllium (Be), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), gallium (Ga), iron (Fe), lithium (Li), lead (Pb), manganese (Mn), nickel (Ni), selenium (Se), silver (Ag), strontium (Sr), thallium (Th), uranium (u), vanadium (v) and zinc (Zn)) were quantified. Concentrations of 12 elements in fingernails and/or toenails were significantly higher in the mine worker group, in particular As, Co and Cu in both toenails and fingernails. In the mine worker group specifically, As concentrations in both fingernails and toenails were higher in males. Most metals also had a strong positive correlation overall. Both fingernails and toenails appear as interesting biomonitoring matrices for multielement exposure assessment with an impact of different variables, such as mining exposure and sex, on internal levels. The study also highlighted the importance of further human exposure assessment related to artisanal gold mining in Mali, including the identification of other environmental sources of exposure.

Should you buy gold stocks or paper gold?

We analyze which type of gold investment is better for investors by studying the determinants of returns on gold mining stocks (gold stocks) and gold exchange-traded commodities (gold ETCs) over the period from March 2012 to February 2024. We find that gold ETCs outperform gold stocks in both returns and risk, and respond significantly more positively to economic policy uncertainty (EPU), offering investors more favorable safe-haven properties. Gold stocks are also more sensitive to oil price increases than are gold ETCs, and their relative price performance is negatively related to both oil price changes and Gold VIX. We conclude that investing in gold stocks is less suitable for investors who buy gold as a safe-haven asset.

Heavy metal contamination in eggs on poultry farms and ecological risk assessment around a gold mine area in northern Thailand

The aim of this study was to analyze and compare the Hg, Pb, Cd, and Mn levels in egg feed, soil, and water among laying hens, laying ducks, and free-grazing duck farms in contaminated and uncontaminated areas. This study revealed that the Hg concentration in the eggs of free-grazing ducks was significantly greater than that in the eggs of laying hens and ducks in both contaminated and uncontaminated areas. However, the Pb and Mn levels in the eggs of laying ducks and free-grazing ducks were significantly greater than those in the eggs of laying hens in the contaminated area. Unfortunately, the Hg, Pb, Cd, and Mn concentrations in the feed, soil, and water from these three farms in both areas were not significantly different (P > 0.05). Hg and Cd were confirmed to be enriched in the egg albumin fraction, while Pb and Mn were found mainly in the egg yolk. However, egg consumption from free-grazing duck farms was the riskiest to Hg, Pb, and Mn contamination in the contaminated area. Additionally, the ecological risk factor (ER) in the soil revealed that all the farms were at considerable to high environmental risk for Cd except for Hg and Pb. Although the potential ecological risk index (RI) indicated a moderate risk for all farms in both contaminated and uncontaminated areas, these results were not consistent with our hypothesis. Therefore, the information gained in this study could be useful for setting up mitigation strategies and making decisions about public health concerns related to health hazards, especially for ecological risk assessments of heavy metal contamination.

Gold prospectivity mapping using “SWARA” model on geophysical datasets in parts of Ilesa Schist belt, Southwestern Nigeria

This study employed a knowledge–driven model (stepwise weight assessment ratio analysis (SWARA)) for the prospectivity mapping of gold in parts of Ilesa Schist belt, Southwestern Nigeria. Aeromagnetic, aero-radiometric and remote sensing (Atmospheric Spaceborne Thermal Emission and reflection Radiometer (ASTER) data) datasets were utilized for this study. Data enhancement techniques were performed on the aeromagnetic data to produce the lineament map of the study area. Also, analyses of the aeroradiometric and ASTER datasets were used in delineating hydrothermally altered zones in the study area. Lithology, lineament density, hydrothermal alteration and slope were the factors considered to produce the gold potential map of the study area using the SWARA model for weight assignment. The study showed that NE–SW trending structures aid the transportation of hydrothermal and mineralizing fluids in the study area. Furthermore, gold mineralisation is observed to occur majorly on the granitoids. From the SWARA model, weight assignment results showed that the factors influencing gold mineralisation in descending order of importance are hydrothermal alteration, lithology, lineament density and slope. The produced gold mineralisation map based on the weight assignment classified the study area into five classes: background, low, moderate, high and very high with the southern, western and northwestern axis of the study area having moderate to very high potential of gold mineralisation. Qualitative validation using mining pits showed 73 % success rate while quantitative validation utilizing linear regression model showed a success rate of 74 % substantiating the reliability of the model.

Gold Mineralisation and their Lithological Controls at Nagavi Area, Gadag Schist Belt, in Karnataka, India

Dharwar craton is located in southern India is part of the Dharwar-Singhbhum proto-continent and is known for its complex tectonic and structural controls. It’s made up of two distinct parts, Western Dharwar Craton (WDC) and the Eastern Dharwar Craton (EDC) house several schist belts. Many of these schist belts, such as the Kolar schist belt, Hutti schist belt, Chitradurga schist belt and the Gadag schist belt, are auriferous. In such schist belts, gold occurs in association with sulphides such as pyrite, pyrrhotite, arsenopyrite and chalcopyrite. Gold mineralization in these belts is found to occur in different lithologies. The Gadag schist belt is composed dominantly of metabasalt in its western half and meta sediments in the eastern half. Quartz-carbonate veins are observed to cut across these lithologies as well as the Banded Iron Formations (BIFs). This paper aimed to study the gold mineralization in different lithologies of the Gadag schist belt and found that metabasalts and BIFs are the dominant rocks hosting gold. It is also observed that mineralization is strata-bound. Most of the places’ auriferous sheared zones were observed in the study area. In Nagavi area, BIF hosted gold mineralization is observed, and major gold concentration varies from &lt;21 to &lt;26 ppb (parts per billion). Pyrite occurs as characteristic cubic crystals and as clusters of small grains. In carbonated sheared anorthosite, the rock is fine to medium-grained and in-equigranular. It consists of simple to polysynthetically twinned subhedral (100-200 by 400-600 μm) laths (~40-45%) set in a groundmass of irregular anhedral grains of secondary carbonate (~35-40%), chlorite (~8-10%), opaque (~5-7%) and accessory epidote and quartz.

Models for analysing the economic impact of ore sorting, using ROC curves

The past decade has seen a renewed possibility of using machine learning algorithms to solve a large collection of problems in several fields. Data acquisition for mining operations has increased with the growth in sensor-based technologies, and therefore the amount of information available for mining applications has dramatically increased. Ore sorting equipment is available for separating ore from waste based on differences in physical properties detected by a real-time analyser. The separation efficiency depends on the contrast in these properties. In this study we investigate the application of machine learning models trained using data from the output of a dual-energy X-ray ore sorting apparatus at a gold mine. The particles were first hand-sorted into ore and gangue classes based on their mineralogical composition. Classification models were then used to help decide the balance between the number of true and false positives for ore in the concentrate, with a view to economic parameters, using their receiver operator characteristic (ROC) curves. The results showed AUC (area under the ROC curve) scores of up to 0.85 for the classification models and a maximum reward condition Fpr/Tpr around 0.5/0.9 for a simplified economic model.

Optimizing the cut-off grade for tabular gold deposits, considering the South African gold tax and mineral resource royalty regime

The South African mineral resource royalty system, initiated in 2010, employs a hybrid ad valorem approach tied to profitability ratios. This rate is then applied to the total revenue from mineral sales. In this article we explore how the profitability ratio in the mineral resource royalty formulae interacts with the gold tax formula as applied to South African gold mines, devising a strategy for cut-off grade optimization. The study focuses on nine narrow, tabular-reef (Witwatersrand) gold mines. The approach involves a mixed-integer cut-off grade optimizer utilizing Excel Solver, incorporating relevant royalty and income tax formulae. Different mineral resource royalty cost scenarios were examined. Ignoring these costs in the break-even analysis lowers the cut-off grade but slightly boosts profits compared to considering expected costs. The developed optimizer model, recognizing the profitability aspect of the mineral resource royalty and income tax formulae, yielded a 6% lower cut-off grade than the base case. This is significant for increasing mine life. While the profit differences are marginal (0.2% compared to the break-even base case), substantial improvements were noted: a 6% increase in stope tons above cut-off grade, and a 4% rise in total revenue. Enhanced resource utilization (3% extra gold kilograms) reduces necessary development and overall costs, allowing for a reduction in the cut-off grade and ultimately, more profit.

Energy Performance Indicator of a Gold Mining Industry in Indonesia

Energy Performance Indicator of a Gold Mining Industry in Indonesia

Effect of Sodium Cyanide and Jin Chan Chemicals on Gold Gain from Ore

In this article, experiments were carried out on samples taken from two different gold mines located in İzmir Province, Dikili District Çukuralan Locality and Eskişehir Province Sivrihisar District Kaymaz Site. Jin Chan, a new chemical approach with sodium cyanide (NaCN), comparatively evaluated leaching kinetics, gold recovery efficiencies and chemical consumption in the course of leaching. In the study using hydrometallurgical methods; the leaching studies with Çukuralan ore, the optimum parameters were observed at a 40% solid/liquid ratio and 300 mg/l Jin Chan concentration, and gold was recovered with a yield of 90.89%. Hereby, Jin Chan consumption was 0.72 kg/t. In NaCN, on the other hand, the optimum parameters were achieved at a solid/liquid ratio of 40% and a concentration of 300 mg/l NaCN, and gold was obtained with a yield of 91.98%. NaCN consumption was 0.31 kg/t. In the leaching studies with Kaymaz ore, the optimum parameters were reached at 40% solid/liquid ratio and 300 mg/l Jin Chan concentration, and gold was recovered with an 81.55% yield. Jin Chan chemical consumption is seen at 1.27 kg/t. In NaCN, on the other hand, the optimum parameters were achieved at a solid/liquid ratio of 40% and a concentration of 300 mg/l NaCN, and gold recovery was achieved with a yield of 82.86%. NaCN consumption is calculated at 0.95 kg/t.

Green tech soil analysis: a comparison of potentially toxic element contents among urban, agricultural, and gold mining areas in the Eastern Brazilian Amazon.

Artisanal gold mining can lead to soil contamination with potentially toxic elements (PTEs), necessitating soil quality monitoring due to environmental and human health risks. However, determining PTE levels through acid digestion is time-consuming, generates chemical waste, and requires significant resources. As an alternative, portable X-ray fluorescence (pXRF) offers a faster, more cost-effective, and sustainable analysis. This study compared total As, Ba, Cr, Cu, Fe, Mn, Ni, Pb, Sr, Ti, V, and Zn obtained from pXRF with their pseudo-total contents obtained through acid digestion (USEPA method 3051A) in areas influenced by artisanal gold mining in the Eastern Amazon, Brazil. pXRF data and machine learning algorithms were used to predict extractable Cu, Fe, Mn, and Zn. Linear regression models were fitted to compare the two methods, and random forest and support vector machine techniques were used to predict extractable contents. The best regression model fits for the pseudo-total PTE contents were those for Cu, Fe, Mn and Pb in agricultural areas (R2 > 0.80); Fe and Mn in gold mining residue (R2 > 0.70); and Ba, Cu and Mn in urban areas (R2 > 0.80). The best models for predicting the extractable PTE contents were those for Cu (R2 = 0.72; RMSE = 2.58mgdm-3) and Zn (R2 = 0.71; RMSE = 1.44mgdm-3) in agricultural areas and for Zn (R2 = 0.72; RMSE = 0.43mgdm-3) in gold mining residue. The results demonstrated that pXRF can characterize and predict PTE contents in mining-impacted areas, offering a sustainable approach to soil quality analysis.

Geochemical Evidence of Ore-Forming Processes in the Shuiyindong Gold Deposit of Southwest Guizhou Province, China.

The Shuiyindong deposit is one of the ultralarge Carlin-type gold deposits in Southwest Guizhou Province, China. Gold mineralization mainly occurs in the Permian Longtan Formation and the early Triassic Yelang Formation. It is controlled by both strata and faults. Detailed studies of the mineralogy and geochemistry characteristics of the Shuiyindong deposit are conducted to investigate the ore-forming process. Arsenian pyrite and arsenopyrite are the main Au-hosting minerals. Three types of pyrite can be recognized, including euhedral and subhedral pyrite, framboidal pyrite, and bioclastic pyrite. The euhedral and subhedral pyrite is the main Au-hosting type. The Au appears as a solid solution (Au+) and natural nanoscale gold (Au0) in the sulfide minerals. The Co/Ni ratios of sulfides (0.07-3.13) reveal that the ore-forming fluids were mainly affected by hydrothermal activity, but magmatic activity cannot be excluded. Organic matter in the ores is abundant (0.11-3.04%), which might provide sulfur for pyrite and favor an increase in the porosity and permeability of the host rocks by releasing organic acids. The REE and trace element results suggest that halogens (F and Cl) were contained in the reducing magmatic hydrothermal fluids. The sulfur isotopic data (from -8.64‰ to 27.17‰) suggest that the source of sulfur is complicated and is probably a combination of a magmatic source, the reduction of marine sulfate, and bacterial sulfate reduction. The Pb isotopic data of the sulfides indicate that Pb is from a mixture of crust and mantle sources. The obvious enrichment zones exist along the boundary faults in the geochemical map of As, implying that As may originate from the deep crust and then move to the strata with basinal fluids. By combining these results, it can be inferred that the ore-forming fluids were a mixture of basinal and deep source fluids. A probable ore-forming model of the Shuiyindong gold deposit is established.

Effect of Different Sizes and Heights on the Removal Efficiency of Composite Clay Filter for Gold Mine Site Wastewater Remediation

Wastewater from mining-related activities contains toxic elements that require remediation, and most available wastewater filters have inconsistent flow rates and removal efficiency due to their thickness. This study, therefore, examined the effect of height and size on the flow rate and removal efficiency of a clay composite filter for wastewater remediation. The developed clay filter and its composites were characterized using various techniques such as X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The XRF analysis showed that the clay contained 91.38% major minerals, including iron oxide (Fe2O3), aluminum oxide (Al2O3), and silica (SiO2), which could enhance the filtration process. Additionally, FTIR revealed that both the clay and the filter are rich in functional groups, including kaolinite and illite, which could promote the filtration process. Further analysis showed that the filters had an average adsorption rate of 87.32%, an average flow rate of 0.891 L/hr, and an average removal efficiency of 99.6%. An increase in the height of a small-diameter filter resulted in a 0.21% increase in removal efficiency, while for larger diameters, the removal efficiency decreased by 0.11%. Conversely, increasing the diameter of a short filter increased the efficiency by 0.25%, while for taller filters, the removal efficiency decreased by 0.07%. Therefore, this work demonstrated that both height and diameter have noticeable effects on flow rate: as height increases, flow rate decreases, and as diameter increases, flow rate increases. The filter's efficiency is somewhat affected by both height and diameter, with a small increase in efficiency noted at greater heights and a slight decrease in efficiency noted at larger diameters.

Production of low-sulphur tailings by hydrocycloning

Acid mine drainage (AMD) is an environmental problem in gold mines containing sulphur minerals. The potential for acid drainage in tailings facilities must be considered when studying their dry closure. Therefore, controlling the sulphur content in the final layer of tailings deposition has the potential to prevent AMD after closure. In this context, the rougher flotation tailings were hydrocycloning in a pilot plant in a gold mining company to assess the potential for generating modified tailings with low-sulphur content. A total of 10 samples were composited over one hour of pilot plant operation. The hydrocyclone overflow showed an average reduction of 36.2% in sulphur content and an average metallurgical recovery of 20.0%. The underflow had an average increase in sulphur content of 16.8% and 80.0% metallurgical recovery. These results demonstrated the possibility of generating modified tailings with reduced sulphur content through hydrocycloning.

Plant Agency in the Guianas: Attraction, Assault, and Animacy

This article uses ethnographic and ethnobotanical methods to examine relationships between animate and agentive plants and human beings among the Makushi, Pemon, Karinya, and other Indigenous and mixed-Indigenous peoples in the Guianas. It considers representations of these plants and related ontologies in the archival record and contrasts these accounts with more recent ethnographic descriptions based on the authors’ fieldwork across Guyana and Venezuela. It thinks about these plants as agentive beings (with regard to animist ontologies and sometimes physical properties) within a variety of contexts. Today, the territories of these Indigenous peoples tessellate with extractive frontiers, which center around gold, diamond, and bauxite mining, as well as oil prospecting, forestry, and plantation agriculture. In this context, these plants emerge as active and animate agents. They also emerge as such agents in contexts of subsistence, shamanism, and assault sorcery, as well as sexual and romantic attraction, which can act with or without human impetus. The question arises as to the nature of the relationships between such plants and their users, for example, shamans ( piaimen), assault sorcerers ( kanaima), hunters, gardeners, and miners, within a variety of contexts. Based on the authors’ long-term fieldwork, the article examines animate plants and argues that they evince special botanical agencies among the Indigenous communities with whom the authors have worked in the Guianas. How are animate plants positioned within these practices and contexts? And how do they exert agency therein as plant persons?

Integrated Geophysical Investigation using Aero-radiometric and Electrical Methods for Potential Gold mineralization within Yauri/Zuru Schist Belts, Kebbi State NW Nigeria

This study used aero-radiometric, 2D electrical resistivity tomography (ERT), and induced polarization (IP) methods to delineate gold mineralization potential. The study also confirmed and followed-up on regions with major structural features identified in previous aeromagnetic studies in the area. A half-degree airborne radiometric data of sheet 118_Yelwa from the NGSA, which contains three radioelements (%K, eTh, and eU) were used in this study. These datasets were processed and analyzed with Oasis Montaj Grid Math expression builder to obtain the %K_ratio_eTh and Ternary grid anomalies. The results identified zones E and F as hydrothermally altered regions that may harbour gold mineralization. These findings were consistent with the regions of major structural features identified in previous aeromagnetic studies in the area. The zones were located in the eastern parts of Ngaski, Yauri (Yelwa), Shanga, and Agwara, as well as Magama's northwest region. However, zone F1 (the eastern portion of Ngaski/Yauri) has been further investigated using 2ERT and IP detailed geophysical methods in a dipole-dipole configuration. The results of geoelectric techniques along profiles 1, 2, and 3 identified the major gold mineralization potential zones, which were labeled A1, A, and C. These regions have low/high resistivity and chargeability signatures, and could thus be interpreted as potential target zones for metallic mineral exploration, particularly gold mineralization. The regions are located in the northern part of Mararraba and southwest of the Jinsani areas of Kebbi State.

How Does Small-Scale Mining Stabilize Rural Livelihoods in Sub-Saharan Africa? The Case of Mozambique

This paper examines the linkages between subsistence farming and artisanal and small-scale mining (ASM) – low-tech, labor-intensive mineral extraction and processing – in sub-Saharan Africa, focusing on the case of Mozambique. While the body of literature on this subject is burgeoning, it is comprised mostly of conceptual pieces and country case studies that rely heavily on qualitative data. Focusing on Manica Province, long an epicentre of small-scale gold mining activity in Mozambique, the paper showcases the value of including complementary quantitative data in analyses of ASM-farming linkages in rural sub-Saharan Africa. In particular, quantitative data that provide detail on the demographical composition of communities engaged in both ASM and agriculture, and which shed light on the spending patterns of households involved, could go a long way toward enriching dialogues on this subject, and, in the process, yield more effective (and, indeed, representative) rural development and poverty alleviation strategies in the region. The data gathered in Manica Province provide a more nuanced picture of how the ages and educational levels of household heads, and the sizes of their families, shape views on ASM and agriculture in gold-rich sections of Mozambique. Studies exploring the linkages between ASM and agriculture in sub-Saharan Africa that feature both qualitative and quantitative data provide greater clarity on the role each activity could play in tackling some of the region’s broader development challenges, including food insecurity and (building) community resilience.

Geochemical Modeling and Quality Assessment of the Surface Waters from the Mouhoun River System, Burkina Faso: Implications of Water–Rock Interactions and Anthropogenic Activities

Major ion and heavy metal geochemistry was used to investigate the factors that control the Mouhoun River water quality in western Burkina Faso. Major cation concentrations was in the following decreasing order: Ca2+&gt; Na+&gt; K+&gt; Mg2+, reflecting silicate weathering. However, relatively high HCO3- and SO42- concentrations could be related to dissolution of calcite and sulfide minerals, respectively. The average heavy metal concentrations in the riverine system were in the following order: FeT&gt;Ag&gt;Mn&gt;Zn&gt;Pb&gt;Cu&gt;Ni&gt;AsT&gt;Cr&gt;Hg&gt;Co&gt;Cd with FeT and Ag exceeding the World Health Organization permissible limits. Concentrations of all heavy metals, except Cr, were higher in the Mouhoun system compared to the average world river concentrations. Adsorption and speciation models showed that Zn, Ag, Cd, Co, Cr and Ni are likely to remain in their free ionic forms, and thus posing serious threats to aquatic life and human health. Ag-Hg-Ni-Cd association around Poura and Tenado on the principal component plot suggested that the widespread artisanal gold mining in these areas may have contributed to these metals’ loading. In contrast, NH4+, Pb, Cu, Cr, AsT and Zn were clustered around a densely populated and industrialized Kou watershed, pointing to agricultural and industrial sources of these pollutants. Furthermore, the Kou River had the highest metal index followed by Tenado, Samendeni, Poura and Boromo. Hence, the chemistry of the Mouhoun River and its tributary appears to be mainly controlled by population density and various anthropogenic activities taking place in their drainage basins. The findings could provide avenues for sound and sustainable water resource management in a water scarce semi-arid environment.

Accounting for informalization in Africa's extractive industry: Evidence from Ghana's small‐scale gold mining sector during the colonial period

AbstractIn this paper, we draw on the accountability and institutional theories to explicate the informalized state of Ghana's small‐scale gold mining sector as an exemplar of informalization of the extractive industry in Africa during the colonial period. We present a critical and historical perspective on the role of colonial subjugation that took the form of discriminatory policies and lack of accountability, in laying the foundations for the current challenges of continuous informalization of the indigenous gold mining sector and its implications on livelihoods, the economy and the environment in Ghana. We analyzed archival data on the mining industry in Ghana, consisting of official correspondences between colonial bureaucrats in Britain and Ghana, as well as colonial policies on mining, interpreted through the lenses of institutional theory. Specifically, we used records comprising letters, mineral policies, mineral output, and labor relations in the Gold Coast during the colonial period as well as minutes of meetings held by those governing mining enterprises that operated in Ghana before 1957. We also drew on periodic reports of the Ghana Chamber of Mines and their member enterprises, Government of Ghana white papers, parliamentary records among others. We found that the colonial authority, as the new institutional power with vested interest in the extractive industry, adopted discriminatory policies that banned small‐scale gold mining by indigenous population in Ghana, marginalizing the sector's operation to the advantage of foreign large‐scale gold miners. We demonstrate that the control of mineral resources by the colonial authority under new ownership structures disenfranchised the indigenous population and their right to the mineral resources of the Gold Coast. We argue that this institutionalized discriminatory policy, and the resulting lack of accountability is largely responsible for the ongoing informalization of Ghana's small‐scale gold mining sector. This paper contributes to the corpus of critical and historical scholarship that investigates the role of racialization and accountability during colonial period, but with notable distinction that departs from specific professional or disciplinary perspectives. Instead, it focuses on the colonial subjugation and exploitation of the small‐scale gold mining sector and its ongoing informalization that traces its roots to the era of British colonial rule in Ghana. It reiterates the need for accountability for these historical inequalities affecting the small‐scale mining operators, to facilitate the sector's formalization and to effectively control and manage the myriads of negative impacts associated with it.

Proposal for a framework for environmental zoning of areas near gold mines based on the distribution of potentially toxic elements, pollution indices, and bioindicators: a case study in Antioquia, Colombia

Gold mining, even under strict environmental regulations, inevitably causes environmental impacts and liabilities. To address this, the study proposes a framework for environmental zoning around gold mines based on the distribution of potentially toxic elements (PTEs), pollution indices, and bioindicators. Soil samples were collected from municipalities affected by gold mining projects, and concentrations of As, Cd, Pb, and Cr were measured. Then, the Pollution Load Index (PLI) was calculated. A plant model was used for the biomonitoring of PTEs, and the Plant Vigor Index (PVI) was determined. Finally, environmental zoning was proposed through geospatial analysis combining PTEs, PLI, and PVI values. The concentrations of PTEs were as follows: As ranged from 1.7 to 892, Cd from 0.1 to 65.2, Pb from 18.5 to 2345, and Cr from 5.4 to 118.4. Spearman’s rank correlation showed significant relations (ρ > 0.76) between bioindicators and PTE concentrations and PLI. The PVI correlated significantly with PTE concentrations (ρ − 0.41 to − 0.67) and PLI (ρ − 0.65). The municipalities were categorized into three zones: highly contaminated, moderately contaminated, and minimally contaminated. Overall, the environmental zoning maps serve as a management tool for environmental monitoring.

Impact of climatic seasons on the dynamics of carbon, nitrogen and mercury in soils of Brazilian biomes affected by gold mining

Land use change, especially mining activities, contributes to anthropic CO2 emissions, leading to decreased carbon (C) storage and loss of biodiversity. Artisanal gold mining associated with the use of mercury (Hg) for amalgamation may change soil organic matter (SOM) contents, and the release of Hg into the environment generates serious environmental problems. Changes in soil biogeochemistry due to C loss and seasonal climate fluctuations affect Hg dynamics and can either increase or decrease its availability. Therefore, our objective was to evaluate the impact of mining on SOM and Hg geochemistry in four Brazilian biomes. We evaluated the dynamics of C and Hg in the dry and rainy seasons of mining and pasture areas by combining spectroscopic, thermogravimetric, and chemical extraction. The critical role of SOM in Hg retention and the influence of climatic seasons on C and nitrogen (N) stocks were highlighted, along with the availability of Hg in solution. Key findings indicated a 50 % reduction in soil C stocks in mined areas, exacerbated during dry seasons, which also saw up to a 70 % increase in bioavailable Hg. SOM played a critical role in Hg retention, with Hg availability closely linked to soil C stability. These results highlight the environmental degradation linked to mining and suggest strategies to mitigate these impacts by increasing SOM and immobilizing Hg. Amalgamation of gold directly into ore, as in the Amazon, has generated great soil Hg stocks, while Hg availability appeared to be governed by soil C stability. This information can serve as a basis for choosing strategies to mitigate environmental degradation caused by changes in land use in mining activities to promote increase in SOM and to immobilize Hg contents.