Impacts of metal mining on river systems: a global assessment

Accurate prediction of spatial distribution of soil heavy metal in complex mining terrain using an improved machine learning method

Accurate prediction of heavy metals (HMs) spatial distribution in mining areas is crucial for pollution management. However, predicting the spatial distribution of HMs remains a significant challenge in mining areas with complex terrain and variable contaminant transport pathways. This study aims to optimize the spatial prediction of arsenic (As) distribution in the Shimen realgar mining area, the largest in Asia, by integrating machine learning models with kriging interpolation and feature selection techniques. The results show that the Random Forest (RF) model achieved the best performance in predicting soil As concentration, with an R2 of 0.84 for the test data. Incorporating environmental variables improved the spatial prediction accuracy, with RF (R2 = 0.76, RMSE = 24.68 mg/kg) and Random Forest Regression Kriging (RFRK) (R2 = 0.78, RMSE = 23.46 mg/kg) outperforming ordinary kriging and geographically weighted regression kriging. Importance analysis and recursive feature elimination further optimized the model, leading to a 5 % increase in R2 and a reduction of RMSE by 8 %-12.4 %. The optimized RFRK model accurately captured the spatial distribution of As in the mining area, revealing the outward diffusion pattern of As from the smelting plant. The findings highlight the critical role of feature selection in improving prediction accuracy in highly polluted and complex terrain regions, an aspect that has often been overlooked in previous studies. This study provides a practical framework for spatial prediction of contaminants in similar areas, enhancing the understanding of pollution distribution.

A bioinspired microbial taste chip with artificial intelligence-enabled high selectivity and ultra-short response time

Real-time water pollution monitoring is crucial as global water pollution has become an urgent issue endangering the health of humanity. Microbial taste chips are promising for water pollution monitoring due to the advantages of short response time and real-time monitoring capability. However, although more than 200 journal research articles on microbial taste chips have been reported to date, sensor selectivity, which is the foremost critical parameter, remains an unsolved challenge even after utilizing gene-editing techniques. In addition, the response time is long and takes at least 3 min. Herein, we report a breakthrough to solve the selectivity challenge by a bioinspired wireless microfluidic microbial taste chip with artificial-intelligence(AI)-enabled high selectivity. Utilizing gated recurrent unit(GRU)-based deep learning algorithms, we demonstrate a classification accuracy of 98.9% for Cu2+, Pb2+, and Cr6+ by harnessing the different temporal output current patterns of the chips to different pollutants. A shortest 48-s response time is achieved, 3.75 times shorter than the fastest previously reported counterpart. The chip enables real-time sensing of Cu2+, Pb2+, and Cr6+ with high accuracy and linearity. Combined with a small footprint and wireless connectivity, the chip may find applications in real-time quantitative heavy metal ions in water monitoring and contribute to global efforts in fighting water pollution.

Abandoned mine clusters and their intersection with Indigenous peoples' land rights in Australia

Empirical research on the intersection of Indigenous peoples and abandoned mines has primarily focused on the impacts of individual, large-scale mines in the settler states of Australia, Canada and the United States. In contrast, research on the extent and effects of dense clusters of relatively small, abandoned mines has been largely overlooked. Australia has 50,000+ abandoned mines and their overlap with Indigenous peoples' legally recognised rights to land has not been mapped or quantified. This study presents a novel methodology to map and quantify this intersection using the state of Queensland as a case study. Through spatial data and document analysis, we find that 54.8 % of Queensland's abandoned mines are located where Indigenous peoples have rights to land and we identify five dense clusters that warrant further examination. Our findings provide an empirical basis for regulators, mining companies, land use planners and Indigenous communities to address significant policy and practice shortcomings. Recognising abandoned mines as a pressing governance challenge-not merely a historical remnant-is a crucial step towards advancing environmental sustainability, Indigenous land justice, and equitable land management.

Geopolitics and mine waste: An overview and future research directions

This paper examines a critical yet underexplored perspective on resource geopolitics by focusing on mine waste-one of the world's largest waste streams by volume. Traditional studies of resource geopolitics emphasise the governance of raw materials production, trade and supply chains. Our approach positions mine waste as a factor shaping twenty-first century geopolitics and global power dynamics. To demonstrate the analytical value of making this connection, we explore two domains: geopolitical strategies and alliances; and sovereignty and justice. We illustrate how mine waste both reflects and reinforces global inequalities, revealing power dynamics relating to the economic and environmental burdens placed on vulnerable regions and the sacrifice zones created by market and regulatory gaps. New geopolitical strategies such as on-shoring and friend-shoring reallocate mine waste-related liabilities, exposing the intersection of sovereignty, justice, and international relations. We conclude that mine waste is a strategic liability and a tool of state power, pivotal to foreign policy and geopolitical dominance in the context of critical resource competition. As contemporary geopolitics continues to evolve, we call for interdisciplinary research that better reconciles the global demand for minerals with the rights and interests of host countries, Indigenous peoples and local communities.

Efficient capture and detoxification of gaseous arsenic trioxide from flue gas using silicomanganese alloy dust

This study aims to develop efficient capture materials for gaseous arsenic trioxide (As2O3(g)) that can prevent arsenic poisoning in selective catalytic reduction (SCR) systems and reduce atmospheric arsenic emissions from coal-fired power plants. One kind of metallurgical dust from a silicomanganese alloy plant (named as SiMnD) was found to be cost-effective and environmentally friendly for As2O3(g) removal from flue gas for the first time. The sorbent showed excellent performance for gaseous arsenic trioxides capture with a good capacity of 13.82 mg/g at 450 °C in 60 min, which was better than the other reported metal oxides at high temperature. The As2O3(g) capture capacity in 12-h continuous test reached as high as 118.16 mg/g without penetration, and the sorbent showed good long-term durability and pretty good resistance to high concentrations of nitric oxide (NO), sulfur dioxide (SO2) and carbon dioxide (CO2). The sorbent also exhibited good recyclability even after five regeneration cycles. Nearly 92% of As2O3(g) was transformed into manganese (II) pyroarsenate (Mn2As2O7), manganese arsenate (MnAsO4) and diarsenic pentoxide (As2O5) after capture with lower toxicity. The results of Toxicity Characteristic Leaching Procedure (TCLP) and five-step sequential extraction demonstrated that spent SiMnD exhibited low arsenic bioavailability, indicating reduced environmental mobility of arsenic species. Trimanganese tetroxide (Mn3O4) and blythite (Mn3Mn2(SiO4)3) were the most essential active component for As2O3(g) removal and detoxification. The optimal As2O3(g) capture temperature of SiMnD was 450 °C which was suitable to be applied before SCR with little operating cost. SiMnD was proved to be one excellent capture and detoxification agent for As2O3(g) in flue gas at a lower temperature with promising application prospects.

Integrating mining district data into ecological security pattern identification: a case study of Chenzhou

Resource-intensive cities face significant ecological challenges due to mining activities, which degrade landscapes, pollute ecosystems, and disrupt ecological security patterns. This study proposes a process for identifying ecological security patterns (ESP) in mining cities, integrating landscape risk assessment, remote sensing ecological quality evaluation, and mining district spatial data. We introduce the ecological source index (ECSI) to identify ecological sources in Chenzhou and construct an ecological resistance surface (ERS) by incorporating mining district locations. Using circuit theory, we map key ecological corridors and nodes, establishing the ecological security framework for Chenzhou. Our findings show 2,903 km² of primary ecological sources, 1,735 km² of secondary ES, and 2,124 km² of tertiary ES, along with 90 ecological corridors (1,183.66 km), 22 inactive corridors (983.37 km), 3 major river corridors, 68 pinch points, and 80 barriers. The ecological sources are organized in a "dominant source with multiple subsidiary cores" structure, connected by a "three horizontal and four vertical" corridor network. Ecological sources are primarily located in the east, while corridors, pinch points, and barriers are concentrated in the west. Barriers are mainly urban areas, mining zones, and farmland, while pinch points occur in narrow corridor sections, especially near towns and mining areas. Mining activities cause localized shifts and fragmentation of ecological corridors. We propose recommendations for mining management, such as implementing strict mining approval processes, constructing artificial ecological corridors, and expanding ecological channel boundaries in pinch point clusters. These findings provide essential guidance for ecological restoration and sustainable development in resource-dependent cities.

Global soil pollution by toxic metals threatens agriculture and human health

Toxic metal pollution is ubiquitous in soils, yet its worldwide distribution is unknown. We analyzed a global database of soil pollution by arsenic, cadmium, cobalt, chromium, copper, nickel, and lead at 796,084 sampling points from 1493 regional studies and used machine learning techniques to map areas with exceedance of agricultural and human health thresholds. We reveal a previously unrecognized high-risk, metal-enriched zone in low-latitude Eurasia, which is attributed to influential climatic, topographic, and anthropogenic conditions. This feature can be regarded as a signpost for the Anthropocene era. We show that 14 to 17% of cropland is affected by toxic metal pollution globally and estimate that between 0.9 and 1.4 billion people live in regions of heightened public health and ecological risks.

Global and regional patterns of soil metal(loid) mobility and associated risks

Soil contamination by metals and metalloids (metal[loid]s) is a global issue with significant risks to human health, ecosystems, and food security. Accurate risk assessment depends on understanding metal(loid) mobility, which dictates bioavailability and environmental impact. Here we show a theory-guided machine learning model that predicts soil metal(loid) fractionation across the globe. Our model identifies total metal(loid) content and soil organic carbon as primary drivers of metal(loid) mobility. We find that 37% of the world's land is at medium-to-high mobilization risk, with hotspots in Russia, Chile, Canada, and Namibia. Our analysis indicates that global efforts to enhance soil carbon sequestration may inadvertently increase metal(loid) mobility. Furthermore, in Europe, the divergence between spatial distributions of total and mobile metal(loid)s is uncovered. These findings offer crucial insights into global distributions and drivers of soil metal(loid) mobility, providing a robust tool for prioritizing metal(loid) mobility testing, raising awareness, and informing sustainable soil management practices.

Historical mining towns: The establishment of 'Soil Planning Areas' for the risk management of contaminated soil

Historical mining towns face financial challenges with the proposed Soil Monitoring Law of the European Union, which will require the management of soil contamination, since remediating soil in densely populated towns and cities is challenging. We compared the environmental impact of sulfide ore mining in the urban area of Outokumpu in Finland with that of other European sites, focusing on soil contamination. Soil sampling revealed that mine tailings were historically used in road construction. The threshold values of Cu, Ni, and Zn were exceeded at several points, with the highest Cu content reaching 2733 mg/kg. Groundwater and surface water contamination was also evident, mainly due to the lack of a proper protective structure in tailings to prevent acid mine drainage. A preliminary risk assessment suggests health risks from unintentional soil ingestion and dust inhalation. However, the issues in many historical mining towns are more severe if they contain high levels of As or Pb which are more toxic than those of concern in Outokumpu. The historical mining town of Freiberg in Saxony, Germany, has been regulated as a 'Soil Planning Area', where limit values have been provided based on land use scenarios. The regional handling and re-use of excavated soil is based on contamination categories, with the tightest restrictions for the areas where the As content exceeds 340 mg/kg. We suggest 'Soil Planning Areas' to be established in historical mining towns facing similar challenges as a first step to mitigate environmental and health risks with reasonable economic resources.

Geological resource production constrained by regional water availability

Although the global economy requires geological resource mining, production has substantial environmental impacts, including the use of regional available water. In this study, we shed light on the global production capacity of 32 mined geological resources, considering regional water availability as a constraint. We found that current resource mining greatly exceeds regional water constraints for several, notably copper (37% of current production exceeds available water capacity) in 2010. Changing the location of production to regions of lower water stress would alleviate current exceedances of water constraints; however, considering economic factors shows that this is not always feasible. Future demand for geological resources is expected to require a considerable increase in water consumption. Considering the constraints of water resources in geological resource production is crucial for sustainability.

Environmental effects of the Kakhovka Dam destruction by warfare in Ukraine

The use of water as a weapon in highly industrialized areas in the Russo-Ukrainian war has resulted in catastrophic economic and environmental damages. We analyze environmental effects caused by the military destruction of the Kakhovka Dam. We link field, remote sensing, and modeling data to demarcate the disaster's spatial-temporal scales and outline trends in reestablishment of damaged ecosystems. Although media attention has focused on the immediate impacts of flooding on society, politics, and the economy, our results show that toxic contamination within newly exposed sediments of the former reservoir bed poses a largely overlooked long-term threat to freshwater, estuarine, and marine ecosystems. The continued use of water as a weapon may lead to even greater risks for people and the environment.

Assessing temporal shifts in trophic diversity in fish assemblages after the Fundão dam collapse

The rupture of the Fundão dam stands as one of the most significant environmental disasters of its kind on a global scale, profoundly affecting the aquatic ecosystem of Doce River Basin. By employing stable isotopes of carbon and nitrogen, we were able to trace matter and energy flow within ecosystems. In this study, we assessed the spatial and temporal variation, between 2020 and 2022, in species richness and trophic diversity in areas exposed (along a gradient in the main channel of the river) or unexposed (control sites in tributaries systems) to the mine ore tailings in the Doce River Basin. We tested the hypothesis that tailings reduce species richness, and that trophic stability is negatively affected by mining tailings. To estimate trophic stability for each sampling site, we calculated the standard ellipse area (SEA) and six community-wide metrics based on stable isotopes. The three regions studied presented distinct patterns on trophic diversity. Control sites exhibited stability in trophic metrics over time. Affected regions close to the rupture of the dam exhibited significant fluctuations on all six community-wide metrics analyzed than the affected regions farther from the rupture. Sites close to the rupture exhibited lower species richness, affecting mainly herbivores and piscivores. Our findings show the potential of using the isotopic approach in monitoring the ecological recovery of impacted ecosystems.

Contamination and source-specific health risk assessment of soil heavy metals in the middle and upper reaches of the Heihe River Basin of China

Anthropogenic activities drive heavy metal contamination in soil, making source-specific apportionment essential for managing health risks in rapidly urbanizing areas. This study focuses on the novel task of quantifying health risks from specific sources of heavy metal contamination and visualizing the spatial patterns of human activities' impact on heavy metal contamination and health risks. It combined multiple analytical techniques, including pollution indices, health risk assessments, and bivariate local indicators of spatial association analysis. Additionally, the absolute principal component score-multiple linear regression model, integrated with a human health risk assessment, was employed to quantify health risks and evaluate the contributions of specific sources. Results revealed that Cd and As were at moderate contamination levels, while Zn, Cu, and Ni showed low contamination. Despite generally low contamination levels, moderately to heavily contaminated areas were identified in the southern region correlated with human activities. Although both non-carcinogenic and carcinogenic risks were low for both children and adults, Cr and As were still the main contributors to health risks, primarily through ingestion, with children being at a greater risk compared to adults. The health risks were primarily linked to four sources: traffic and mining, natural sources, agricultural activities, and industrial sources. Industrial (children: 27.47%; adults: 31.96%) and agricultural activities (children: 27.11%; adults: 24.01%) were the primary contributors to non-carcinogenic risks, while the carcinogenic risks were mainly contributed by agricultural activities (children: 40.21%; adults: 40.14%). Therefore, controlling industrial and agricultural activities is crucial to safeguarding public health during sustainable regional development.

Habitat recovery from diverted acid mine drainage pollution determined by increased biodiversity of river and estuarine benthic species

Acid mine drainage (AMD) is a frequent cause of ecological damage to many river and estuarine habitats. Once AMD pollution is halted our understanding of subsequent habitat recovery requires long-term ecological assessment. This study examines the consequences of diverting AMD away from a highly contaminated river and estuary using water quality and ecological data from pre- and post-diversion sample periods. 10-12 years following diversion, water quality and benthic macroinvertebrate biodiversity significantly improved at all sample sites of the river, indicative of ecological recovery but upstream sites that were closer to the pollution source were less improved. However, redirection of the AMD into a nearby stream channel caused an almost complete loss of benthic macroinvertebrates. Habitat recovery at the river estuary was demonstrated by increased richness of infaunal invertebrates and rocky shore species, including crustaceans, barnacles and mollusc species. Measurements of copper bioaccumulation in the barnacle Austrominius modestus showed a significant reduction in present day samples compared to those collected before AMD diversion. This study shows that within a decade, an estuarine and river system can demonstrate ecological recovery from AMD pollution, yet within this time period, recovery did not fully match uncontaminated sites.

Discriminating foliar adhered from metabolised Pb when monitoring vegetation exposed to windborne contamination

Monitoring heavy metals in vegetation near mining or industrial sites is crucial for detecting plant contamination; requiring discrimination between metals adhered to foliar surfaces from the internal concentrations. We investigated key factors that might contribute to lead (Pb) accumulation in leaves of local vegetation near a Pb mine: (i) distance from the pollutant source, (ii) morphological characteristics of leaf surfaces, (iii) their susceptibility to Pb loss by washing, and (iv) the effect of contrasting washing reagents in Pb removal. Native plant species were sampled at three field locations, possessing different leaf surface morphologies: glabrous (smooth), resinous (waxy) and hirsute (hairy). After washing with Citranox, EDTA or deionised water, Pb contents were assessed by ICP-OES and SEM-EDX. We observed an order of Pb (and other metals) retention from hirsute > resinous > glabrous, and found: i) greater Pb accumulation in leaves near the mine due to particulate matter (PM) deposition; ii) hirsute leaves retain the highest PM-Pb; iii) higher Pb removal (10-fold) by Citranox and EDTA compared to water; and iv) hirsute leaves retained considerable PM-Pb underneath trichomes despite washing, leading to Pb overestimation. Therefore, for accurate Pb monitoring, washed glabrous leaves are best indicated due to their negligible PM retention.

Biomonitoring of the Paraopeba river: Cytotoxic, genotoxic and metal concentration analysis three years after the Brumadinho dam rupture - Minas Gerais, Brazil

The rupture of Vale S.A. mining tailings dam in Brumadinho, Brazil, in January 2019 had significant environmental impacts on the Paraopeba River basin. Additionally, severe floods in early 2022 contributed to the transport of particles in the river. This study aimed to evaluate the cytotoxic and genotoxic potential of Paraopeba River water. Thus, the Allium cepa test system was applied, along with physicochemical analyses, flow cytometry, and metal concentration, comparing the results between the rainy and dry seasons three years after the dam rupture. The tests were conducted on water samples collected during three periods: January 2022, July 2022, and January 2023, at five points along the river and its tributaries. Allium cepa seeds were exposed to the collected water samples, as well as negative (water) and positive (trifluralin) controls. Cytotoxicity was evaluated using the mitotic index and flow cytometry, and genotoxicity by the chromosomal alterations index. The analysis of metals and physicochemical parameters revealed that most values complied with current regulations. However, there were exceptions, with ammonia levels exceeding the permitted limits at all points in the three collections. High levels of aluminum, iron and nitrite were found at most points, before and after the dam collapse, mainly during the rainy season. This indicates the impact of rainfall on water quality, which increases the transport of contaminating particles, probably resulting from human activities and the high concentration of nitrogen compounds released into the Paraopeba River. The results of the bioassay suggest a relatively low cytotoxic and genotoxic potential of the samples evaluated. However, this study highlights the continuous contamination of the river by unidentified anthropogenic factors, requiring continuous monitoring and analysis to track the evolution of water quality and its environmental effects.

Intersection of Wildfire and Legacy Mining Poses Risks to Water Quality

Mining and wildfires are both landscape disturbances that pose elevated and substantial hazards to water supplies and ecosystems due to increased erosion and transport of sediment, metals, and debris to downstream waters. The risk to water supplies may be amplified when these disturbances occur in the same watershed. This work describes mechanisms by which the intersection of mining and wildfire may lead to elevated metal concentrations in downstream waters: (1) conveyance of metal-rich ash and soil to surface waters, (2) increased dissolution and transport of dissolved metals due to direct contact of precipitation with mine waste, (3) increased erosion and transport of metal-rich sediment from mining waste, (4) remobilization of previously deposited metal-contaminated floodplain sediment by higher postfire flood flows, and (5) increased metal transport from underground mine workings. Predicted increases in wildfire size, frequency, and burn severity, together with the ongoing need for metal resources, indicate that improved mapping, monitoring, modeling, and mitigation techniques are needed to manage the geochemical hazard of the intersection of wildfire and mining and implications for water availability.

Heavy metals: toxicity and human health effects

Heavy metals are naturally occurring components of the Earth's crust and persistent environmental pollutants. Human exposure to heavy metals occurs via various pathways, including inhalation of air/dust particles, ingesting contaminated water or soil, or through the food chain. Their bioaccumulation may lead to diverse toxic effects affecting different body tissues and organ systems. The toxicity of heavy metals depends on the properties of the given metal, dose, route, duration of exposure (acute or chronic), and  extent of bioaccumulation. The detrimental impacts of heavy metals on human health are largely linked to their capacity to interfere with antioxidant defense mechanisms, primarily through their interaction with intracellular glutathione (GSH) or sulfhydryl groups (R-SH) of antioxidant enzymes such as superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), glutathione reductase (GR), and other enzyme systems. Although arsenic (As) is believed to bind directly to critical thiols, alternative hydrogen peroxide production processes have also been postulated. Heavy metals are known to interfere with signaling pathways and affect a variety of cellular processes, including cell growth, proliferation, survival, metabolism, and apoptosis. For example, cadmium can affect the BLC-2 family of proteins involved in mitochondrial death via the overexpression of antiapoptotic Bcl-2 and the suppression of proapoptotic (BAX, BAK) mechanisms, thus increasing the resistance of various cells to undergo malignant transformation. Nuclear factor erythroid 2-related factor 2 (Nrf2) is an important regulator of antioxidant enzymes, the level of oxidative stress, and cellular resistance to oxidants and has been shown to act as a double-edged sword in response to arsenic-induced oxidative stress. Another mechanism of significant health threats and heavy metal (e.g., Pb) toxicity involves the substitution of essential metals (e.g., calcium (Ca), copper (Cu), and iron (Fe)) with structurally similar heavy metals (e.g., cadmium (Cd) and lead (Pb)) in the metal-binding sites of proteins. Displaced essential redox metals (copper, iron, manganese) from their natural metal-binding sites can catalyze the decomposition of hydrogen peroxide via the Fenton reaction and generate damaging ROS such as hydroxyl radicals, causing damage to lipids, proteins, and DNA. Conversely, some heavy metals, such as cadmium, can suppress the synthesis of nitric oxide radical (NO·), manifested by altered vasorelaxation and, consequently, blood pressure regulation. Pb-induced oxidative stress has been shown to be indirectly responsible for the depletion of nitric oxide due to its interaction with superoxide radical (O2·-), resulting in the formation of a potent biological oxidant, peroxynitrite (ONOO-). This review comprehensively discusses the mechanisms of heavy metal toxicity and their health effects. Aluminum (Al), cadmium (Cd), arsenic (As), mercury (Hg), lead (Pb), and chromium (Cr) and their roles in the development of gastrointestinal, pulmonary, kidney, reproductive, neurodegenerative (Alzheimer's and Parkinson's diseases), cardiovascular, and cancer (e.g. renal, lung, skin, stomach) diseases are discussed. A short account is devoted to the detoxification of heavy metals by chelation via the use of ethylenediaminetetraacetic acid (EDTA), dimercaprol (BAL), 2,3-dimercaptosuccinic acid (DMSA), 2,3-dimercapto-1-propane sulfonic acid (DMPS), and penicillamine chelators.

Mobilization of porewater Pb and Zn in response to seasonal wetting and drying within contaminated floodplains

The mobility and bioavailability of metal contaminants such as lead (Pb) and zinc (Zn) is impacted by their interactions with other sediment constituents such as iron (Fe), sulfur (S), and organic matter, which depend on sediment redox conditions. Understanding the role that water level fluctuations have on redox conditions and subsequent impacts on metal mobility is critical for predicting impacts of increased wetting and drying cycles resulting from climate-related changes or management actions. This study measured the sediment-porewater partitioning of Pb and Zn in the Coeur d'Alene River basin downstream of the Bunker Hill Superfund Site under both flooded and seasonally dry conditions. The results show that both time of year and hydrology are important when considering metal exposure risks in contaminated floodplains. For Pb, seasonal spring flooding appears to mobilize dissolved Pb in both seasonally inundated and permanently inundated areas due to increases in sediment-derived Pb that undergo desorption processes from suspended Fe and DOC. For Zn, oxygenation of floodplain sediments in the fall drives elevated dissolved Zn year-round due to limited ZnS precipitation. Wetting-drying cycles had a significant impact on Zn mobility, which could be exacerbated by climate-driven hydrological changes or floodplain management actions.

Impacts of mining on the diversity of benthic macroinvertebrates - A case study of molybdenum mining area in Luanchuan county

Mineral exploitation is one of the human activities that seriously affect freshwater ecosystems. It is of great significance to study the impact of mining on the α and β diversity of macroinvertebrates. This study reveals the response of taxonomic and functional α and β diversity of macroinvertebrates to mining activities in the Luanchuan molybdenum mining area. A total of 40 sets of macroinvertebrates, sediment and water samples in the Taowan North River (TR), Yu River (UR) and Hongluo River (HR) in the molybdenum mining area were collected. The results show that: 1) the mining activities led to obvious differences in the environmental factors of the three rivers. The heavy metals in the sediments and water bodies of TR and UR showed different degrees of exceedance, while there was no exceedance of heavy metals in HR; 2) The taxonomic and functional α diversity was much lower in the TR and the UR than in the HR. The concentrations of heavy metals in sediments and water bodies were significantly negatively correlated with the taxonomic and functional α diversity; 3) Mineral extraction resulted in significant differences in macroinvertebrate β diversity among the three rivers. The taxonomic and functional β diversity of the macroinvertebrate communities in TR and UR was much higher than that in HR. The turnover and nestedness of functional β diversity showed significant differences. Functional β diversity was more obviously affected by heavy metal exceedance than taxonomic β diversity. Nestedness were more sensitive to exceedance of heavy metals than turnover. The results of this study can provide a theoretical basis for ecological restoration and protection of rivers in mining areas.

Five years after the Brumadinho dam collapse: Evaluation of water quality based on combined analysis of land use and environmental data

The collapse of the dam in the Paraopeba River watershed in 2019 triggered significant concerns regarding water quality in the region. This study aimed to assess, five years after the disaster, the effects on water quality and understand the underlying factors of environmental pressure contributing to the observed changes. To perform the evaluation, the study utilized surface water quality data pre-disaster (2012-2018) and post-disaster (2019-2023), environmental data regarding the identification of high-polluting potential industries operating in the region of interest, and land use for the watershed as a combined evaluation. Nonparametric statistical tests Kruskal-Wallis, complemented by Dunn's, were employed to assess the significance of changes in water quality parameters post-collapse. The results indicate a relatively stable baseline scenario of land use dominated by agriculture and pasture, with minor changes observed in forest cover and urban development. However, post-collapse assessments showed significant variations in water quality parameters, with turbidity exceeding conformity levels by up to 68 % (over 100 NTU), dissolved iron (Fe) by up to 70 % (over 0.3 mg.L-1), manganese (Mn) by up to 91 % (over 0.1 mg.L-1), dissolved aluminum (Al) by up to 83 % (over 0.01 mg.L-1), and lead (Pb) by up to 26 % (over 0.01 mg.L-1). Statistical tests suggested possible effects of the dam collapse on turbidity, pH, dissolved Fe, Mn, and dissolved Al. Temporal analysis showed constant effects on water quality, with notable increases in dissolved Fe and Mn concentrations observed upstream post-disaster and persistent impacts downstream. New mining activities licensed after 2019 may have contributed to the deterioration of water quality, highlighting the relevant relationship of anthropogenic activities and the environmental disaster in the Paraopeba River watershed.

Byproduct-to-Host Ratios for Assessing the Accessibility of Mineral Resources

Mineral resources are essential for reaching net-zero ambitions by 2050. There is a rising diversity of metals in electricity generation and storage technologies, as well as for mobility technologies. However, little is known about the future supply of minor elements historically mined in low volumes such as indium, tellurium, germanium, or tantalum. Those minor elements are found in lower concentrations in the ores of major elements and therefore rarely form economic deposits on their own. Such elements are often produced as byproducts of a host (or "target commodity", which underpins the bulk of a mine's profitability) in ore, e.g., in porphyry ore, tellurium is a byproduct where copper is the host. As a result, the primary supply of those minor elements depends on the supply of the major elements. Such dependency has not been accounted for in scenarios of the mineral supply. To address this gap, we developed a methodology to harmonize scattered data of mineral resource estimates and to calculate the mass ratio between the byproduct and the host in ores and concentrates, called the byproduct-to-host (BtH) ratio. We collected crude ore tonnage and element grades, among other key data, from the state-of-the-art literature and publicly available mining company reports. Our data set covers 3422 deposits across 141 countries providing 22 275 BtH ratios. The future supply of minor elements can be derived by multiplying the primary production of host elements by the developed BtH ratios, noting the limitations of data representativity. The open-access nature of this work facilitates the enrichment and update of this data set in the coming years.

Source-risk and uncertainty assessment of trace metals in surface sediments of a human-dominated seaward catchment in eastern China

Current total concentration-based methods for source attribution and risk assessment often overestimate metal risks, thereby impeding the formulation of effective risk management strategies. This study aims to develop a framework for source-specific risk assessment based on metal bioavailability in surface river sediments from a human-dominated seaward catchment in eastern China. Metal bioavailability was quantified using chemical fractionation results, and source apportionment was conducted using the positive matrix factorization (PMF) model. Risk assessment integrated these findings using two indices: the Potential Ecological Risk Index (PERI) and the Mean Probable Effect Concentration Quotient (mPEC-Q), with uncertainty addressed via Monte Carlo simulations. Results indicated that average total concentrations of Cu, Pb, Zn, Cr, Hg, Cd, and As exceeded their respective background levels by 1.63 to 15.00 times. The residual fraction constituted the majority, accounting for 53.84 % to 77.79 % of total concentrations, suggesting significant natural origins. However, source apportionment revealed a predominant contribution from anthropogenic activities, including industrial smelting, agricultural practices, and atmospheric deposition. The contributions were found to vary between 5.35 % and 40.03 % when the total concentration was adjusted to bioavailable content. Total concentration-based PERI/mPEC-Q assessments indicated high/moderate risk levels, decreasing to considerable/low risk levels with bioavailability adjustment. Hg and Cd were identified as priority metals. Further incorporating source appointment parameters into the risk assessment, industrial smelting was identified as the primary contributor, accounting for 66.06 % of total risk by total concentration and 65.63 % by bioavailability. This underscores the role of bioavailability in mitigating risk overestimation. Monte Carlo simulations validated industrial smelting as a major risk contributor. This study emphasizes the importance of considering bioavailability in the source-risk assessment of sediment-metals, crucial for targeted risk management in urbanized catchment areas.

Neglected pathways of heavy metal input into agricultural soil: Water-land migration of heavy metals due to flooding events

Flooding, carrying sediments, inundates farmlands across the world due to extreme adverse weather conditions. The casualties and property damage associated with flooding are important direct impacts. However, there is currently insufficient understanding of the remobilization and distribution of heavy metals (HMs) caused by flooding. Few studies have specifically considered flooding as a pathway for HMs contamination of soil. Herein, a novel methodological framework for revealing the input pathways of HMs in agricultural soils in mining-intensive areas is proposed and applied. Flooding is considered one of the pathways for HMs inputs during source apportionment. The results demonstrated a high degree of overlap between the distribution characteristics of major HMs in agricultural soils and sediments. The degree of soil Cd pollution was significantly positively correlated with the inundation depth in the flooded area. It took 8.4-11.5 times of flood inundation or 98.5-119.9 years of accumulation of atmospheric deposition to reach HMs contamination levels in the soil of the study area. Flooding brought in most of the soil Cd, while atmospheric deposition was the primary input pathway for soil Pb and Zn. Our results identified the role of flood inundation on the input of HMs in mining-intensive areas. These results demonstrated the value of our framework for studying the impact of flooding on HMs in agricultural soils from the perspective of input pathways, providing new insights not only into identifying the sources of soil HMs but also into enhancing understanding of the impact of flooding on soil environments. With the potential increase in the frequency and intensity of flooding inundating farmlands in the future, it is essential to consider flooding as a pathway for HMs inputs in order to comprehensively assess their environmental impact.

Toxic Metals and Metalloids in Food: Current Status, Health Risks, and Mitigation Strategies

PURPOSE OF REVIEW

Exposure to toxic metals/metalloids, such as arsenic (As), cadmium (Cd), and lead (Pb), through food consumption is a global public health concern. This review examines the contamination status of these metals/metalloids in food, assesses dietary intake across different populations, and proposes strategies to reduce metal/metalloid exposures throughout the food chain.

RECENT FINDINGS

For the general population, dietary intake of metals/metalloids is generally lower than health-based guidance values. However, for vulnerable populations, such as infants, children, and pregnant women, their dietary intake levels are close to or even higher than the guidance values. Among different food categories, seafood shows higher total As, but largely present as organic species. Rice accumulates higher As concentration than other cereals, with inorganic As (iAs) and dimethylarsinic acid (DMA) being the main As species. Methylated thioarsenate species, such as dimethylmonothioarsenate, have also been detected in rice. The distribution of iAs and DMA in rice shows geographical variation. Additionally, seafood and cocoa products generally contain more Cd than other food, but seafood consumption does not significantly increase in adverse health effects due to its high zinc and iron content. Compared to As and Cd, Pb concentrations in food are generally lower. To minimize the health risks of metal/metalloid exposure, several strategies are proposed. Food contamination with toxic metals/metalloids poses significant concerns for human health, particularly for vulnerable populations. This review provides scientific evidence and suggestions for policy makers to reduce human exposure of metals/metalloids via dietary intake.

Distribution of heavy metals in the sediments of Ganga River basin: source identification and risk assessment

Sediment serves as a heavy metal store in the riverine system and provides information about the river's health. To understand the distribution of heavy metal content in the Ganga River basin (GRB), a total of 25-bed sediment and suspended particulate matter (SPM) samples were collected from 25 locations in December 2019. Bed sediment samples were analyzed for different physio-chemical parameters, along with heavy metals. Due to insufficient quantity of SPM, the samples were not analyzed for any physio-chemical parameter. The metal concentrations in bed sediments were found to be as follows: Co (6-20 mg/kg), Cr (34-108 mg/kg), Ni (6-46 mg/kg), Cu (14-210 mg/kg), and Zn (30-264 mg/kg) and in SPM, the concentrations were Co (BDL-50 mg/kg), Cr (10-168 mg/kg), Ni (BDL-88 mg/kg), Cu (26-80 mg/kg), and Zn (44-1186 mg/kg). In bed sediment, a strong correlation of 0.86 and 0.93 was found between Ni and Cr, and Cu and Zn respectively and no significant correlation exists between organic carbon and metals except Co. In SPM, a low to moderate correlation was found between all the metals except Zn. The risk indices show adverse effects at Pragayraj, Fulhar, and Banshberia. Two major clusters were formed in Hierarchal Cluster Analysis (HCA) among the sample points in SPM and bed sediment. This study concludes that the Ganga River at Prayagraj, Banshberia, and Fulhar River is predominately polluted with Cu and Zn, possibly posing an ecological risk. These results can help policymakers in implementing measures to control metal pollution in the Ganga River and its tributaries.

Uncontrolled Illegal Mining and Garimpo in the Brazilian Amazon

Mining has played an important role in the economies of South American countries. Although industrial mining prevails in most countries, the expansion of garimpo activity has increased substantially. Recently, Brazil exhibited two moments of garimpo dominance over industrial mining: 1989-1997 and 2019-2022. While industrial mining sites occupied ~ 360 km2 in 1985 but increased to 1800 km2 in 2022, a 5-fold increase, garimpo mining area increased by ~ 1200%, from ~ 218 km2 in 1985 to ~ 2627 km2 in 2022. More than 91% of this activity is concentrated in the Amazon. Where almost 40% of the sites are five years old or younger, this proportion increases to 62% within Indigenous lands (ILs). Regarding the legal aspect, at least 77% of the 2022 extraction sites showed explicit signs of illegality. Particular attention must be given to the Kayapo, Munduruku, and Yanomami ILs. Together, they concentrate over 90% of the garimpo across ILs.

The Effects of Model Insoluble Copper Compounds in a Sedimentary Environment on Denitrifying Anaerobic Methane Oxidation (DAMO) Enrichment

The contribution of denitrifying anaerobic methane oxidation (DAMO) as a methane sink across different habitats, especially those affected by anthropogenic activities, remains unclear. Mining and industrial and domestic use of metals/metal-containing compounds can all cause metal contamination in freshwater ecosystems. Precipitation of metal ions often limits their toxicity to local microorganisms, yet microbial activity may also cause the redissolution of various precipitates. In contrast to most other studies that apply soluble metal compounds, this study investigated the responses of enriched DAMO culture to model insoluble copper compounds, malachite and covellite, in simulated sedimentary environments. Copper ≤ 0.22 µm from covellite appeared to cause immediate inhibition in 10 h. Long-term tests (54 days) showed that apparent methane consumption was less impacted by various levels of malachite and covellite than soluble copper. However, the medium-/high-level malachite and covellite caused a 46.6-77.4% decline in denitrification and also induced significant death of the representative DAMO microorganisms. Some enriched species, such as Methylobacter tundripaludum, may have conducted DAMO or they may have oxidized methane aerobically using oxygen released by DAMO bacteria. Quantitative polymerase chain reaction analysis suggests that Candidatus Methanoperedens spp. were less affected by covellite as compared to malachite while Candidatus Methylomirabilis spp. responded similarly to the two compounds. Under the stress induced by copper, DAMO archaea, Planctomycetes spp. or Phenylobacterium spp. synthesized PHA/PHB-like compounds, rendering incomplete methane oxidation. Overall, the findings suggest that while DAMO activity may persist in ecosystems previously exposed to copper pollution, long-term methane abatement capability may be impaired due to a shift of the microbial community or the inhibition of representative DAMO microorganisms.

Hydrological classification of mine pit lakes using modelling experiments

With the growing global prevalence of open-pit mining activities, there is an increasing necessity for sustainable mine life cycle plans with an early outlook towards mine closure. A major consideration in mine closure planning is the potential formation of lakes in the mine void and how these "pit lakes" can be managed to minimise risks and, if possible, create benefits. Understanding the long-term interactions between pit lakes, groundwater, and surface water systems is essential for that purpose. While numerous site-specific studies have been undertaken, there have been no studies that aim to provide a general, broadly applicable understanding of how pit lake hydrology relates to geographical context, and no efforts to hydrologically classify pit lakes using geographical criteria. This research employs an integrated generic pit lake water balance model to examine mine pit lake interactions with the surrounding surface water and groundwater. Simulating 243 scenarios, the influence of five input factors (climate, hydraulic conductivity, regional groundwater level, catchment area and pit slope) on pit lake behaviour up to 6000 years beyond the closure of the mine was considered. The assessment focused on four pit lake hydrological attributes once the system reached equilibrium: water level, time to equilibrium, the fraction of days where the pit recharges groundwater, and the fraction of days where there is surface overflow from the lake. All scenarios were assigned to one of five hydrological classes based on the interactions between the pit lake and the surrounding surface water and groundwater. Our findings show that, in many contexts, general data on climate type and subsurface hydraulic conductivity can yield reliable predictions of a pit lake's long-term hydrological classification without having to develop a detailed, site-specific pit lake model. The classification needs improvements in non-arid climates where inter-annual variation in rainfall is pronounced. The pit lake classification is particularly valuable for first-pass risk assessments to determine whether site-specific modelling is required.

A dual-signaling surface-enhanced Raman spectroscopy ratiometric strategy for ultrasensitive Hg2+ detection based on Au@Ag/COF composites

Heavy metal ion pollution poses significant risks to human health and ecological systems, and its monitoring is important. A sensitive and accurate surface-enhanced Raman spectroscopy (SERS) detection assay for Hg2+ was developed using Au@Ag/COF substrates and Y-shaped DNA labeled with two Raman reporters. The Au@Ag NPs in the COF produced robust and uniform E-fields, improving their detection reproducibility. The Y-shaped DNA design increased sensitivity with a low detection limit of 5.0 × 10-16 M by bringing the Raman reporter closer to the substrate surface. Additionally, the use of two Raman reporters allowed for a ratiometric method, improving detection accuracy by detecting both "signal-off" and "signal-on" signals. This selective sensor exhibited excellent recovery in river water, tap water, and milk samples, showcasing its robust biosensing capability for the detection of Hg2+ and its potential for sensing other heavy-metal ions in food and environmental applications.

Diversified Vegetation Cover Alleviates Microbial Resource Limitations within Soil Aggregates in Tailings

Resource demand by soil microorganisms critically influences microbial metabolism and then influences ecosystem resilience and multifunctionality. The ecological remediation of abandoned tailings is a topic of broad interest, yet our understanding of microbial metabolic status in restored soils, particularly at the aggregate scale, remains limited. This study investigated microbial resources within soil aggregates from revegetated tailings and applied a vector model of ecoenzymatic stoichiometry to examine how different vegetation patterns (grassland, forest, or bare land control) impact microbial resource limitation. Five-year vegetation restoration significantly elevated carbon (C) and nitrogen (N) concentrations and their stoichiometric ratios in soil aggregates (approximately 2-fold), although these increases were not translated to in the microbial biomass and its stoichiometry. The activities of C- and phosphorus (P)-acquiring extracellular enzymes in these aggregates increased substantially postvegetation, with the most pronounced escalation in macroaggregates (>0.25 mm). The vector model results indicated soil microbial metabolism was colimited by C and P, most acutely in microaggregates (<0.25 mm). This colimitation was exacerbated by monotypic vegetation cover but mitigated under diversified vegetation cover. Soil nutrient stoichiometric ratios in vegetation restoration controlled microbial resource limitation, overshadowing the impact of heavy metals. Our findings underscore that optimizing resource allocation within soil aggregates through strategic revegetation can enhance microbial metabolism in tailings, which advocates for the implementation of diverse vegetation covers as a viable strategy to improve the ecological development of degraded landscapes.

Thallium isotopic fractionation in soils from a historic HgTl mining area: New insights on thallium geochemistry

Thallium (Tl), a highly toxic heavy metal, which may pose significant environmental threats due to extensive discharge from anthropogenic activities. It is crucial to understand geochemical behavior of Tl in soils for initiating proper measures for Tl pollution control. For this purpose, transport behavior of Tl and its dominant factors in soils collected from a typically Tl-enriched depth profile, surrounding a historical tailing dump near an independent HgTl mine area in China, were investigated by using Tl isotope compositions. Results showed that an overall enrichment of Tl (48.68-375.21 mg/kg) was accompanied with As elevation (135.00-619.00 mg/kg) in the whole depth profile, and Tl and As exhibited co-migration behavior with Fe, S, K, and Rb. Geochemical fractionation of Tl unveiled by sequential extraction further indicated that Mn-/Fe-bearing minerals and clay minerals act as main hosts of Tl in the studied soils. Thallium isotopic composition and its fractionation pattern further revealed that the major contributors to high Tl levels in the depth profile were tailing and lorandite minerals, with mean contribution rate of 51.99% and 42.47%, respectively. These findings facilitate the understanding of Tl transport behavior in highly contaminated environment, providing valuable insights for developing new technologies in mining waste treatment and historical mine reclamation.

Acidophilic sulphate-reducing bacteria: Diversity, ecophysiology, and applications

Acidophilic sulphate-reducing bacteria (aSRB) are widespread anaerobic microorganisms that perform dissimilatory sulphate reduction and have key adaptations to tolerate acidic environments (pH <5.0), such as proton impermeability and Donnan potential. This diverse prokaryotic group is of interest from physiological, ecological, and applicational viewpoints. In this review, we summarize the interactions between aSRB and other microbial guilds, such as syntrophy, and their roles in the biogeochemical cycling of sulphur, iron, carbon, and other elements. We discuss the biotechnological applications of aSRB in treating acid mine drainage (AMD, pH <3), focusing on their ability to produce biogenic sulphide and precipitate metals, particularly in the context of utilizing microbial consortia instead of pure isolates. Metal sulphide nanoparticles recovered after AMD treatment have multiple potential technological uses, including in electronics and biomedicine, contributing to a cost-effective circular economy. The products of aSRB metabolisms, such as biominerals and isotopes, could also serve as biosignatures to understand ancient and extant microbial life in the universe. Overall, aSRB are active components of the sulphur and carbon cycles under acidic conditions, with potential natural and technological implications for the world around us.

The effect of heavy precipitation on the leaching of heavy metals from tropical coastal legacy tailings

The continued growth in demand for mineral resources has led to a large amount of mining wastes, which is a major challenge in the context of carbon neutrality and climate change. In this study, runoff migration, batch leaching, and column experiments were used to investigate the short-, medium-, and long-term leaching of heavy metals from legacy tailings, respectively; the cumulative metal release kinetic equations were established, and the long-term effects of tailings leaching were verified by HYDRUS-1D. In runoff migration experiments, surface dissolution of tailings and the co-migration of adsorbed soil particles by erosion were the main carriers in the early stages of leachate formation (Mn ∼ 65 mg/L and SO42- up to 2697.2 mg/L). Batch leaching tests showed that the concentration of heavy metals in soil leached by acid rain were 0.1 ∼ 22.0 μg/L for Cr, 0.7 ∼ 26.0 μg/L for Cu, 4.8 ∼ 5646.0 μg/L for Mn, 0.3 ∼ 232.4 μg/L for Ni, and 1.3 ∼ 448.0 μg/L for Zn. The results of column experiments indicated that some soluble components and metals with high mobility showed a significant decreasing trend at cumulative L/S ≤ 2. Additionally, the metals have higher leaching rates under TCLP conditions, as shown by Mn > Co > Zn > Cd > Ni > Cu > Pb > Cr. The fitting results of Langmuir equation were closer to the cumulative release of metals in the real case, and the release amounts of Mn, Zn, Co, and Ni were higher with 55, 5.84, 2.66, and 2.51 mg/kg, respectively. The water flow within tailings affects the spatial distribution of metals, which mainly exist in relatively stable chemical fractions (F3 + F4 + F5 > 90 %) after leaching. Numerical simulation verified that Mn in leachate has reached 8 mg/L at a scale of up to 100 years. The research results are expected to provide technical basis for realizing the resource utilization of tailings in the future.

Riparian trees in mercury contaminated riverbanks: An important resource for sustainable remediation management

Mining operations generate sediment erosion rates above those of natural landscapes, causing persistent contamination of floodplains. Riparian vegetation in mine-impacted river catchments plays a key role in the storage/remobilization of metal contaminants. Mercury (Hg) pollution from mining is a global environmental challenge. This study provides an integrative assessment of Hg storage in riparian trees and soils along the Paglia River (Italy) which drains the abandoned Monte Amiata Hg mining district, the 3rd former Hg producer worldwide, to characterize their role as potential secondary Hg source to the atmosphere in case of wildfire or upon anthropic utilization as biomass. In riparian trees and nearby soils Hg ranged between 0.7 and 59.9 μg/kg and 2.2 and 52.8 mg/kg respectively. In trees Hg concentrations were below 100 μg/kg, a recommended Hg limit for the quality of solid biofuels. Commercially, Hg contents in trees have little impact on the value of the locally harvested biomass and pose no risk to human health, although higher values (195-738 μg/kg) were occasionally found. In case of wildfire, up to 1.4*10-3 kg Hg/ha could be released from trees and 27 kg Hg/ha from soil in the area, resulting in an environmentally significant Hg pollution source. Data constrained the contribution of riparian trees to the biogeochemical cycling of Hg highlighting their role in management and restoration plans of river catchments affected by not-remediable Hg contamination. In polluted river catchments worldwide riparian trees represent potential sustainable resources for the mitigation of dispersion of Hg in the ecosystem, considering i) their Hg storage capacity, ii) their potential to be used for local energy production (e.g. wood-chips) through the cultivation and harvesting of biomasses and, iii) their role in limiting soil erosion from riparian polluted riverbanks, probably representing the best pragmatic choice to minimize the transport of toxic elements to the sea.

Photochemical Origins of Iron Flocculation in Acid Mine Drainage

Acid mine drainage (AMD) raises a global environmental concern impacting the iron cycle. Although the formation of Fe(III) minerals in AMD-impacted waters has previously been reported to be regulated by biological processes, the role of abiotic processes remains largely unknown. This study first reported that a photochemical reaction coupled with O2 significantly accelerated the formation of Fe(III) flocculates (i.e., schwertmannite) in the AMD, as evidenced by the comparison of samples from contaminated sites across different natural conditions at latitudes 24-29° N. Combined with experimental and modeling results, it is further discovered that the intramolecular oxidation of photogenerated Fe(II) with a five-coordinative pyramidal configuration (i.e., [(H2O)5Fe]2+) by O2 was the key in enhancing the photooxidation of Fe(II) in the simulated AMD. The in situ attenuated total reflectance-Fourier transform infrared spectrometry (ATR-FTIR), UV-vis spectroscopy, solvent substitution, and quantum yield analyses indicated that, acting as a precursor for flocculation, [(H2O)5Fe]2+ likely originated from both the dissolved and colloidal forms of Fe(III) through homogeneous and surface ligand-to-metal charge transfers. Density functional theory calculations and X-ray absorption spectroscopy results further suggested that the specific oxidation pathways of Fe(II) produced the highly reactive iron species and triggered the hydrolysis and formation of transient dihydroxo dimers. The proposed new pathways of Fe cycle are crucial in controlling the mobility of heavy metal anions in acidic waters and enhance the understanding of complicated iron biochemistry that is related to the fate of contaminants and nutrients.

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.

Metal-contaminated sediment toxicity in a highly impacted Neotropical river: Insights from zebrafish embryo toxicity assays

The Fundão dam collapse was one of the largest mining-related disasters globally. It resulted in the release of mining tailings containing heavy metals, which contaminated the Doce River in southeastern Brazil. This study assessed the effects of acute exposure of Danio rerio embryos to sediments contaminated by mine tailings six years after the Fundão dam collapse. The study sites included P2, P3, and P4 in the upper Doce River, as well as site P1 on the Piranga River, an uncontaminated river. Sediment samples were analyzed for 10 metals/metalloid by atomic absorption spectrometry. In the assays, embryos were exposed to sediment from P1-P4 sites, and uncontaminated quartz was used as control sediment. Various biomarkers were applied to assess biological responses, and the integrated biomarker response (IBR) index was calculated for each site. Sediment samples revealed elevated levels of As, Cr, Cu, Hg, and Ni beyond Brazilian legislation limits. At 96-h exposure, embryo mortality rates exceeded 20% in P1, P2, and P3, higher than the control and P4 (p < 0.0001). Hatching rates ranged from 60 to 80% in P1, P2, and P3, lower than the control and P4 (p < 0.001). Larvae exposed to P2 sediment (closest to the Fundão dam) exhibited skeletal, physiological, and sensory malformations. Neurotoxicity was indicated by increased acetylcholinesterase activity and reduced spontaneous movements in embryos exposed to Doce River sediment. Contamination also increased metallothionein and heat shock protein 70 levels, along with changes in cell proliferation and apoptosis. Principal component analysis showed a good correlation between metals/metalloid in the sediment and larval morphometric endpoints. The IBR index highlighted suitable biomarkers for monitoring metal contamination in fish embryos. Overall, our findings suggest that sediment toxicity following the Fundão dam failure may compromise the sustainability of fish communities in the Doce River.

Legacy effects of historical gold mining on floodplains of an Australian river

The gold rush at the end of the nineteenth century in south-eastern Australia resulted in the mobilization and re-deposition of vast quantities of tailings that modified the geomorphology of the associated river valleys. Previous studies of contamination risk in these systems have either been performed directly on mine wastes (e.g., battery sand) or at locations close to historical mine sites but have largely ignored the extensive area of riverine alluvial deposits extending downstream from gold mining locations. Here we studied the distribution of contaminant metal(loids) in the Loddon River catchment, one of the most intensively mined areas of the historical gold-rush period in Australia (1851-1914). Floodplain alluvium along the Loddon River was sampled to capture differences in metal and metalloid concentrations between the anthropogenic floodplain deposits and the underlying original floodplain. Elevated levels of arsenic up to 300 mg-As/kg were identified within the anthropogenic alluvial sediment, well above sediment guidelines (ISQG-high trigger value of 70 ppm) and substantially higher than in the pre-mining alluvium. Maximum arsenic concentrations were found at depth within the anthropogenic alluvium (plume-like), close to the contact with the original floodplain. The results obtained here indicate that arsenic may pose a significantly higher risk within this river catchment than previously assessed through analysis of surface floodplain soils. The risks of this submerged arsenic plume will require further investigation of its chemical form (speciation) to determine its mobility and potential bioavailability. Our work shows the long-lasting impact of historical gold mining on riverine landscapes.

Environmental pollution and human health risk due to tailings storage facilities in China

Tailings storage facilities (TSFs) represent an anthropogenic source of pollution, resulting in potential risks to both environmental integrity and human health. To date, the environmental and human health risks from TSFs in China have been under-researched. This study attempts to address this gap by developing, and geo-statistically analyzing two comprehensive databases. The first database (I) focuses on failed TSFs; we supply the statistics of environmental damages from 143 TSF failure incidents. Notably, approximately 75 % of the failure incidents involved tailings flows released into water bodies, resulting in a significant exacerbation of environmental pollution. To better inform ecological and human health risks, we present another database (II) for 147 non-failed TSFs to investigate the soil heavy metal contamination, considering 8 heavy metals. The findings reveal that (i) Cd, Pb, and Hg are the prominent pollutants across the non-failed TSF sites in China; (ii) lead‑zinc and tungsten mine tailings storage sites exhibit the most severe pollution; (iii) Pb, Cd, and Ni present noteworthy non-carcinogenic risks to human health; (iv) >85 % of TSF sites pose carcinogenic risks associated with arsenic; and (v) health risks resulting from dermal absorption surpass ingestion for the majority of heavy metals, with the exception of Pb, where ingestion presents a more pronounced route of exposure. Our study presents a comprehensive evaluation of environmental and human health risks due to TSFs, highlighting the necessity for risk assessment of >14,000 existing TSFs in China.

Inhibition photooxidation of pyrite under illumination via altering photogenerated carrier migration pathways: Role of DTC-TETA surface passivation

The oxidation of pyrite is the main cause of acidic mine drainage (AMD), which is a very serious environmental problem in numerous mining areas around the world. Previous studies have shown that passivation agents create a hydrophobic film on the surface of pyrite, effectively isolating oxygen and water. However, the presence of abundant sulfide minerals in tailings ponds may exacerbate AMD when exposed to solar radiation, due to the semiconductor properties of pyrite. It remains uncertain whether the current surface passivation coating can effectively prevent the oxidation of pyrite under light conditions. This paper is the first to investigate the passivation effect as well as the mechanism of surface passivation coating on pyrite under illumination from the perspective of materials science. The results demonstrated that the triethylenetetramine-bisdithiocarbamate (DTC-TETA) passivation coating on pyrite almost completely suppressed the photooxidation of pyrite under illumination by changing the migration path of photogenerated charge carriers. The formation of NC(S)2-Fe chelating groups provides atomic-level interface channels for DTC-TETA to transfer electrons to pyrite and creates a favorable reduction environment for pyrite. Besides, DTC-TETA coating greatly improves the electron-hole pairs recombination efficiency of pyrite, which significantly inhibits the photogenerated electron reduction of oxygen to generate reactive oxygen species (ROS). Moreover, DTC-TETA coating captures the photogenerated holes, avoiding direct oxidation of pyrite by holes. Density functional theory (DFT) calculations revealed that the DTC-TETA coating increases the adsorption energy barrier for oxygen and water. The results extend the existing knowledge on passivation mechanisms on pyrite and hold significant implications for the future screening, evaluation, and practical application of surface passivating agents.

Speciation and Possible Origins of Organosulfur Compounds in Rice Paddy Soils Affected by Acid Mine Drainage

Although sulfur cycling in acid mine drainage (AMD)-contaminated rice paddy soils is critical to understanding and mitigating the environmental consequences of AMD, potential sources and transformations of organosulfur compounds in such soils are poorly understood. We used sulfur K-edge X-ray absorption near edge structure (XANES) spectroscopy to quantify organosulfur compounds in paddy soils from five AMD-contaminated sites and one AMD-uncontaminated reference site near the Dabaoshan sulfide mining area in South China. We also determined the sulfur stable isotope compositions of water-soluble sulfate (δ34SWS), adsorbed sulfate (δ34SAS), fulvic acid sulfur (δ34SFAS), and humic acid sulfur (δ34SHAS) in these samples. Organosulfate was the dominant functional group in humic acid sulfur (HAS) in both AMD-contaminated (46%) and AMD-uncontaminated paddy soils (42%). Thiol/organic monosulfide contributed a significantly lower proportion of HAS in AMD-contaminated paddy soils (8%) compared to that in AMD-uncontaminated paddy soils (21%). Within contaminated soils, the concentration of thiol/organic monosulfide was positively correlated with cation exchange capacity (CEC), moisture content (MC), and total Fe (TFe). δ34SFAS ranged from -6.3 to 2.7‰, similar to δ34SWS (-6.9 to 8.9‰), indicating that fulvic acid sulfur (FAS) was mainly derived from biogenic S-bearing organic compounds produced by assimilatory sulfate reduction. δ34SHAS (-11.0 to -1.6‰) were more negative compared to δ34SWS, indicating that dissimilatory sulfate reduction and abiotic sulfurization of organic matter were the main processes in the formation of HAS.

Assessment of heavy metal accumulation and potential risks in surface sediment of estuary area: A case study of Dagu river

Soil/sediment samples of four different land types were collected from aquaculture land, farmland, industrial land and river bottom sediment in the estuary area of Dagu River. The contents of Cr, Cu, Zn, As, Cd and Pb in 0-30 cm inner surface samples were detected, and the distribution characteristics of heavy metal content in surface soil/sediment of different land use types in the estuary area were analyzed. Local accumulation index method, potential risk index evaluation method and principal component analysis method were used to analyze the pollution status and sources of heavy metals. The results showed that the heavy metal accumulation levels in soil and sediment samples in the study area were As > Cd > Cu > Pb > Zn > Cr, and the heavy metal content exceeded the soil background value in Shandong Province, but the potential risks were all in a low risk state. The main sources of Cr, Zn and As are transportation sources and natural sources, while the main sources of Cd and Pb are agricultural.

Toward a Mechanism-Driven Integrated Framework to Link Human Exposure to Multiple Toxic Metal(loid) Species with Environmental Diseases

The ongoing anthropogenic pollution of the biosphere with As, Cd, Hg and Pb will inevitably result in an increased influx of their corresponding toxic metal(loid) species into the bloodstream of human populations, including children and pregnant women. To delineate whether the measurable concentrations of these inorganic pollutants in the bloodstream are tolerable or implicated in the onset of environmental diseases urgently requires new insight into their dynamic bioinorganic chemistry in the bloodstream-organ system. Owing to the human exposure to multiple toxic metal(loid) species, the mechanism of chronic toxicity of each of these needs to be integrated into a framework to better define the underlying exposure-disease relationship. Accordingly, this review highlights some recent advances into the bioinorganic chemistry of the Cd2+, Hg2+ and CH3Hg+ in blood plasma, red blood cells and target organs and provides a first glimpse of their emerging mechanisms of chronic toxicity. Although many important knowledge gaps remain, it is essential to design experiments with the intent of refining these mechanisms to eventually establish a framework that may allow us to causally link the cumulative exposure of human populations to multiple toxic metal(loid) species with environmental diseases of unknown etiology that do not appear to have a genetic origin. Thus, researchers from a variety of scientific disciplines need to contribute to this interdisciplinary effort to rationally address this public health threat which may require the implementation of stronger regulatory requirements to improve planetary and human health, which are fundamentally intertwined.