Zinc Mine Research Articles

Efficient zinc extraction with novel phenyl phosphate PTOPP in sulfuric acid system

Traditional acidic phosphate extractants (D2EHPA and HEH/EHP) exhibit poor extraction performance under high-acid conditions and require saponification pretreatment to maintain the pH stability of the aqueous phase during the solvent extraction. However, saponification pretreatment produces a large amount of saline wastewater, resulting in high treatment costs and difficulty of the industrial waste salts utilization. Thus, we synthesized an efficient p-tert-octyl phenyl phosphate (PTOPP) extractant suitable for a high-acid system based on phenyl substitution and carbon-chain design. The structure and content of the synthesized products were confirmed to be [(CH3)3CCH2C(CH3)2C6H4O]2P(O)OH (diphenyl phosphate, P10B4, 88.26%) and (CH3)3CCH2C(CH3)2C6H4OP(O)(OH)2 (monophenyl phosphate, DHP10B4, 10.68%) via HRMS, LCMS, and NMR characterization combined with potentiometric titration. After three-stage countercurrent extraction and two-stage countercurrent stripping, the zinc extraction efficiency of PTOPP reached 85%, and the zinc concentration of aqueous phase increased from 20 g/L to 66.53 g/L with a 3.3 enrichment multiple. In comparison, the enrichment multiples of D2EHPA and HEH/EHP under the same conditions were only 1.5 and 1.1, respectively. The zinc extraction mechanism with PTOPP was determined by the slope method and structural characterization of the extracted compound (PTOPP-Zn). During the zinc extraction process, the P-OH and P=O groups in PTOPP interacted with Zn2+ to form Zn–O bonds through proton exchange and coordination reactions, and the molecular formula of the extracted compound was ZnA2·HA. The novel PTOPP significantly improves the zinc extraction performance and achieves a remarkable enrichment effect without saponification pretreatment, thereby avoiding the consumption of NaOH and the discharge of Na2SO4 wastewater. It has promising applications in the fields of low-grade zinc mineral resource recovery and heavy-metal wastewater disposal.

Evaluation of excavation method on point load strength of rocks with poor geological conditions in a deep metal mine

In the field of deep mining engineering, it poses a challenge to promptly determine the mechanical properties of rocks under poor geological conditions through in-situ tests. However, the indirect determination of uniaxial compressive strength (UCS) of rocks can be achieved through the point load strength index (PLSI) test on irregular samples. In the present study, laboratory uniaxial compressive and field PLSI tests were carried out on irregular ore and rock blocks extracted through mechanical mining methods from a stope at a lead–zinc mine in Yunnan Province, China, with a depth of approximately 1000 m. The effects of mechanical excavation and drilling-blasting methods on the PLSI of rocks and ores are compared. It is found that there are significant differences in the point load strength indexes obtained by different excavation methods, and the Is(50) obtained after the mechanical excavation method approximates the actual value of ore and surrounding rocks. Two correction methods were utilized to obtain the point load strength indexes Is(50)-1 and Is(50)-2 of irregular rock samples. The correlation factors (k) linking Is(50) to UCS and Brazilian splitting strength are derived based on testing results. The findings indicate that using the conversion factor (k) recommended by ISRM to predict the UCS of rocks may significantly underestimate the actual strength of rocks in intricate mining environments. This study can serve as a benchmark for analogous deep mining projects.

The future availability of zinc: Potential contributions from recycling and necessary ones from mining

Society's increasing demand for metals led to the discussion as to whether scarcity of raw materials could lead to supply shortages and to which extend circularity can prevent resource depletion. This study investigates the need for and availability of secondary and primary zinc resources under moderate demand growth. A dynamic MFA model simulates future potentials of 9–14 Mt/a zinc recycling and the necessity of 17–22 Mt/a zinc mining in 2050. The MFA model estimates a cumulative required mine production of 500–560 Mt between 2020 and 2050, which equals less than 1% of the extractable global zinc resources estimated within a geological analysis. With continuous exploration contributing to new discoveries, primary zinc is sufficiently physically available. In contrast, recycling is limited to the amounts of post-consumer waste generation. Recycling capacities need to be extended, collection systems optimized and processing efficiencies increased worldwide to realize the full extent of modelled potentials.

Lithogenic and anthropogenic distribution of chemical elements in soils from Pb-Zn mining area. Case study: Kriva River basin, North Macedonia

ABSTRACT Previous studies have shown that certain areas in the territory of the Republic of Macedonia are affected by anthropogenic input of large amounts of various chemical elements into the soil. The area in the vicinity of the Toranica lead and zinc mine near the town of Kriva Palanka, North Macedonia, was studied for the lithogenic and anthropogenic distribution of seventeen elements (Al, As, Ba, Ca, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Sr, V and Zn). Automorphic soil samples (topsoil and subsoil) as well as alluvial sediments and fluvisol samples were collected from the Kriva River basin. Elemental contents were determined by inductively coupled plasma – atomic emission spectrometry (ICP-AES). Data processing was performed using combinations of multivariate statistical methods (factor analysis and cluster analysis). The summarised data for topsoil and subsoil samples show strong correlations between the element distributions in topsoil samples and subsoil samples along the Kriva River basin. Anthropogenic influences were observed in Zone 1 (the area affected by hydrothermal Pb-Zn exploitation). The topsoil layer was affected by enrichment with As, Mn, Pb, and Zn up to 220, 3400, 1700 and 1100 mg/kg, respectively.

Beneficiation Of Artvin-Cerattepe copper-zinc ore by flotation

The Cerattepe (Artvin) mine contains volcanogenic massive sulfide (VMS) deposits in northeastern Turkey. This is a kuroko type deposit located in Late Cretaceous volcanic, intrusive and sedimentary rocks, and has a structure with dense alteration stages. In this study, batch flotation tests were carried out to determine the flotation behavior of a new sample (mix ore), that was the combination of two different ores with different flotation behaviors. The mixed ore contains 2.18% Cu, 1.46% Zn, (Cu/Zn ratio 1.49) 38.35% Fe, and 41.6% S content. An efficient separation of copper minerals from zinc minerals using the conventional selective flotation method could not be achieved due to complex mineralogy and very low liberation degree. Therefore, sequential selective flotation resulted in poor Cu recovery. The effects of flotation parameters such as collector type, collector amount, particle size, and pH conditions, were investigated to obtain a bulk copper-zinc concentrate. The best results were obtained using thionocarbamate (Aero 3894) and dithiophosphine (Aerophine 3418A) collector reagents at d<sub>80</sub>=40 µm particle size. Under optimal conditions (grain size, d<sub>80</sub>=40 µm, pH=11, amount of collector reagent 60 g/t (Aero 3894), frother (MIBC)=50 g/t, solid ratio=32%, flotation time=8 min), a bulk copper-zinc concentrate containing 13% Cu and 9.5% Zn was obtained with a copper yield of 84.4% and a zinc yield of 88.9%. The concentrate mass pull was 13%. After rougher and two-stage scavenger flotation, a concentrate (rougher concentrate + scavenger products) was obtained with a mass pull of 22%. Copper and zinc recoveries of this concentrate were 91.8% and 92.5%, respectively.

Application of X-ray computed tomography scanning in describing partition curves of dense medium cyclones

The partition curve is an important tool to evaluate the separation performance of mineral separators like dense medium cyclones (DMCs). This curve is constructed by float-and-sink (FaS) analysis which involves the use of heavy liquids and suspensions. This traditional technique is hazardous to the environment, laborious, and time-consuming. Here, a new technique using X-ray computed tomography (XCT) scanning was successfully developed and applied for describing the partition curve of a DMC at an Australia-based lead–zinc mineral processing plant. The DMC feed, concentrate and reject streams were sampled and sieved into several size classes. The chemical assays and averaged densities according to each class were analysed by X-ray fluorescence spectrometry and gas pycnometry, respectively. The partition behaviour was investigated by XCT analysis. A model was proposed to determine the mass yield value – an important parameter to define partition curves – by mass balance and reconciliation, which is generally unknown during the sampling of continuous separation processes. From the reconstructed XCT images, we obtained detailed information on individual particles such as volume, surface area, mass, and density. Cumulative mass distribution curves and partition curves of the DMC for different size classes were then constructed and agreed with the FaS analysis. Using the XCT technology can help overcome the issues of the traditional FaS analysis. Moreover, this technology would allow for evaluating DMC separation efficiency with continuous, online, and real-time monitoring and control.

Effect of dissolved unavoidable ions (Fe3+) from iron-containing gangue minerals on dispersion behavior of zinc oxide ore

With the decrease in zinc mineral resources, the secondary resource utilization of zinc tailings has attracted more attention all over the world. However, zinc oxide tailings contain many soluble minerals (limonite, pyrite), resulting in many metal ions interacting with the mineral surface. The effect of unavoidable ions (Fe3+) has become one of the challenges for the efficient separation and recovery of fine zinc oxide. Therefore, it is necessary to identify the effect of Fe3+ on the dispersion behavior of zinc oxide in order to improve the sorting efficiency and effective recycle of secondary resources. This study investigated the effect of Fe3+ on the dispersion behavior of fine smithsonite (zinc oxide). The turbidity experimental results showed that the turbidity of smithsonite was well dispersed in the deionized water, and decreased continuously with the addition of Fe3+. The smithsonite dispersion behavior was damaged by 5 × 10−4 mol/L Fe3+ from pH = 4 to 12. The results of zeta potential showed that the isoelectric point of smithsonite shifted positively from pH = 7.5 to 9.5. X-ray photoelectron spectroscopy (XPS) and solution chemistry analysis indicated that smithsonite was subjected to the action of Fe3+ to generate metal hydroxyl complexes or precipitates. The inter-particle interaction potential barrier of smithsonite at pH = 4 and 10 was 5.745 × 10−19 J and 2.31 × 10−19 J by calculations of DLVO theory, respectively. However, the potential energy of inter-particle interaction between smithsonite particles was less than zero in the presence of Fe3+, which indicated that the presence of iron ions disrupts the dispersion behavior of smithsonite. This study could provide theoretical guidance for the efficient recovery of secondary zinc resources from zinc oxide tailings.

Natural attenuation of heavy metals via secondary hydrozincite precipitation in an abandoned Pb[sbnd]Zn mine

The Aran Valley in Catalonia (Spain) was the site of large-scale Zn, Pb, Cu, Fe, and Ag mining from the late 19th century until approximately 1950. Although mining activities ceased over 70 years ago, some of the abandoned mining relics (e.g. tunnels, processing facilities, and tailings dumps) exhibit elevated concentrations of metals in the associated water systems, thus posing a health risk in the neighboring ecosystem. In this study, the largest underground zinc mine in the Aran Valley (the Victoria Mine) was chosen as a field site to showcase the processes affecting metal mobility in the environment. Three sampling campaigns to the mine (2019, 2020 and 2021) provide a spaciotemporal dataset showing the evolution of solute concentrations through the system along a flow path. Rainwater from the upper catchment flows into the host rock above the mine, dissolving ore materials (primarily Zn (sphalerite) and Fe (pyrite) sulfides with Ni and Cd impurities) that cause elevated Zn, Ni, and Cd concentrations in the water that enters the mine. Precipitation of hydrozincite (Zn5(CO3)2(OH)6) along the gallery where water flows serves as a metal-removal mechanism resulting in significantly diminished metal concentrations (e.g. Zn from 155 to 10 ppm, Ni from 377 to 32 ppb, and Cd from 105 to 22 ppb). Characterization of the solid samples taken from the mine reveals several different morphologies, Zn zonations in hydrozincite (i.e. purity changes), and small amounts of smithsonite (ZnCO3) and calcite (CaCO3). In general, all solids show layering, which is a result of intermittent precipitation of distinct solid products. These precipitation patterns are likely a result of changing solute concentrations and precipitation rates. Variations in rain events change the water residence time in both the host rock and in the gallery, thereby altering the water composition. Solubility experiments and speciation calculations demonstrate that hydrozincite here does not have a constant Keq value, but rather a range of values (30.0 < log[Keq] < 37.68 at 7 °C). This behavior is presumed to be a result of precursor effects as amorphous solids with higher solubilities may form before the structured hydrozincite. Notably, all analyzed solids from the collected mine samples show significant amounts of amorphous material, demonstrated by broad XRD peaks along with significant impurities in the analyzed solids, leading to the hypothesis that there exists a variability in the solubility of hydrozincite beyond a pure end-member value.

Nano-microbubbles and feed size interaction in lead and zinc sulfide minerals flotation

Low recovery of the fully or highly liberated fine particles to the concentrate, and consequently, valuable loss to the tailing is a challenge of flotation industry, majorly due to the low probability of bubble-particle collision. Bubble size significantly affects the efficiency of collision. In this study, the effect of nano-micro bubbles and feed particle size (d80s in the range of 80 to 12 µm), on the lead and zinc minerals recovery, separation efficiency, and valuables loss to the tailings were investigated. The presence of NMBW simultaneously improved concentrate grade and metal recovery to the individual concentrates. Over 14.5% improvements in either lead and zinc recoveries, 0.95% and 2.22% enhancement in lead and zinc concentrate grades, and 15.6% and 8.9% increases in lead and zinc separation efficiencies were, respectively, gained. The application of NMBW, however, reduced metal loss to the tailings, more evident for the finest feed (order based on d100: -38>-75>-106 µm). By increasing NMBW content to 100% of the pulp water, the metal loss to the tailing for the dry-ground feed with the d80 of 12 µm, was decreased from 80.4% to 65.9% in the lead flotation, and from 54.9% to 43.2% in the zinc flotation.

Prediction of ground vibration due to mine blasting in a surface lead–zinc mine using machine learning ensemble techniques

Ground vibration due to blasting is identified as a challenging issue in mining and civil activities. Peak particle velocity (PPV) is one of the blasting undesirable consequences, which is resulted during emission of vibration in blasted bench. This study focuses on the PPV prediction in the surface mines. In this regard, two ensemble systems, i.e., the ensemble of artificial neural networks and the ensemble of extreme gradient boosting (EXGBoosts) were developed for PPV prediction in one of the largest lead–zinc open-pit mines in the Middle East. For ensemble modeling, several ANN and XGBoost base models were separately designed with different architectures. Then, the validation indices such as coefficient determination (R2), root mean square error (RMSE), mean absolute error (MAE), the variance accounted for (VAF), and Accuracy were used to evaluate the performance of the base models. The five top base models with high accuracy were selected to construct an ensemble model for each of the methods, i.e., ANNs and XGBoosts. To combine the outputs of the top base models and achieve a single result stacked generalization technique, was employed. Findings showed ensemble models increase the accuracy of PPV predicting in comparison with the best individual models. The EXGBoosts was superior method for predicting of the PPV, which obtained values of R2, RMSE, MAE, VAF, and Accuracy corresponding to the EXGBoosts were (0.990, 0.391, 0.257, 99.013(%), 98.216), and (0.968, 0.295, 0.427, 96.674(%), 96.059), for training and testing datasets, respectively. However, the sensitivity analysis indicated that the spacing (r = 0.917) and number of blast-holes (r = 0.839) had the highest and lowest impact on the PPV intensity, respectively.

Environmental contamination characteristics of heavy metals from abandoned lead–zinc mine tailings in China

China holds large-scale lead–zinc mineral resources; however, mining activities often cause severe contamination by heavy metals. This study systemically assessed contamination by eight heavy metals (Cu, Zn, Cd, Pb, Cr, Hg, Ni, and As) in mine tailings, soil, and groundwater from 27 contaminated sites across China. Regarding mine tailings, 1% of the mine tailing samples were hazardous waste and 20% were class II non-hazardous waste. Regarding soil, Zn and Pb showed the highest mean concentrations, at 5574.67 mg/kg and 2034.88 mg/kg, respectively. The indexes of geo-accumulation (Igeo) of eight heavy metals ranged from −3.62 to 7.67, while Zn, Pb, and Cd showed the highest environmental risk levels as the priority pollutants. The contamination levels of these heavy metals in groundwater were generally in the order of Zn&amp;gt;As&amp;gt;Pb&amp;gt;Ni&amp;gt;Cd&amp;gt;Cu&amp;gt;Hg&amp;gt;Cr. In this study, 20% of the soil and 10% of the groundwater samples exceeded the corresponding quality limits. The content of heavy metals in soil, groundwater, and mine tailing were positively correlated, demonstrating the main pollution source and transport paths. The pollution levels of heavy metals in soil and groundwater were listed in the foremost and moderate positions compared with similar sites from other countries, respectively. These results may help determine the pollution levels of lead–zinc mining regions and direct the remediation activities of target sites to support the environmental management of abandoned mining and tailing waste in China.

Ecological assessment of soil contamination by heavy metals affected in the past by the lead–zinc mining and processing complex in Kentau, Kazakhstan

Polymetallic ore processing plants are serious sources of heavy metal pollution. The present study examined the degree of pollution of surface soils with the metals zinc, cadmium, lead, and copper in the single-industry town of Kentau, Kazakhstan, where an enterprise for the processing of lead-zinc ore has been operating for a long time. This enterprise ceased operations in 1994, and this study may be of interest in terms of assessing the current ecological state of urban soils after a 27-year period of possible soil self-cleaning processes. The study showed that the surface soils of Kentau retain fairly high concentrations of metals. The maximum detected concentrations of zinc, cadmium, lead, and copper were 592mg/kg, 1.651mg/kg, 462mg/kg, and 82.5mg/kg, respectively. According to the classification of the geoaccumulation index, the soils of the town belong to pollution classes II, III, and IV with moderate and strong pollution. The calculated potential ecological risk factor indicates that cadmium poses a considerable potential ecological risk, while lead showed a moderate ecological risk. In general, according to the obtained values of potential ecological risk factors, metals can be arranged in the following order: Cd > Pb > Zn > Cu. In this study, a five-step sequential extraction procedure by the method of A. Tessier was used, and the mobility factors of metals were calculated. Based on the data obtained, it was found that cadmium and lead have the highest mobility and, consequently, availability for biota in modern conditions, which may pose a potential risk to public health in the town.

Association Between Parameters of Cortisol Metabolism, Biomarkers of Minerals (Zinc, Selenium, and Magnesium), and Insulin Resistance and Oxidative Stress in Women with Obesity.

This is a cross-sectional study with women divided into a group of those with obesity (n = 80) and a control group (n = 94). Statistical analysis was conducted using the SPSS program. There were high values of GPx and TBARS and reduced values of SOD in women with obesity compared to the control group. Obese women showed increased concentrations of cortisol in serum and urine as well as hypozincemia, hyposelenemia, and hypomagnesemia and increased urinary excretion of these minerals. There was a negative correlation between the cortisol/cortisone ratio and erythrocyte zinc and selenium concentrations and a significant positive correlation between GPx and SOD activity and erythrocyte and plasma concentrations of zinc and selenium. The results of the study suggest the influence of adiposity on the increase in cortisol concentrations and the role of this hormone in the compartmentalization of the minerals zinc, selenium, and magnesium. However, the association study does not allow identifying the impact of such action on the antioxidant defense system and insulin sensitivity.

Comparison of Natural Mineral Water From Agrı Province With Sports Drinks

Dehydration emerges due to lack of fluid balance in the body. In addition, minerals such as sodium, potassium, calcium, and magnesium are lost because of dehydration. Athletes lose fluids and electrolytes through sweating during exercise, and replacing the lost fluid and electrolytes is crucial for the continuity of their sports performance. Sports drinks can be consumed by athletes to replace fluid and electrolytes lost during exercise and to improve performance. During this period, consumption of sports drinks minimizes dehydration by restoring the lost mineral and fluid balance. However, the composition of these products, their active ingredients, their effects on sports performance, and their risk factors are matters of debate. This study was carried out in order to compare sports drinks with the local mineral water that comes out naturally in the province of Agri. The mineral determinations of the local mineral water were made using Inductively Coupled Plasma-Mass Spectroscopy (ICP- MS) instruments. As a result of the analyses, the average sodium (Na) value in the local mineral water was 26.6 ppm, and the magnesium (Mg) average was 7.782 ppm. No potassium (K) mineral was detected in Agri local mineral water. Calcium (Ca) mineral average was found to be 65.04 ppm, iron (Fe) mineral average 0.0068 ppm, and zinc (Zn) mineral average 0.02457 ppm. Agri natural mineral water contains minerals in similar amounts to sports drinks. Considering these values, it can be a natural alternative to sports drinks if potassium mineral and glucose is added to its content, so it can be an alternative to sports drinks.

Variations on the diazotrophic community in the rhizosphere soil of three dominant plant species in a lead–zinc mine area

Variations on the diazotrophic community in the rhizosphere soil of three dominant plant species in a lead–zinc mine area

Arbuscular Mycorrhizal Fungi Promote the Degradation of the Fore-Rotating Crop (Brassica napus L.) Straw, Improve the Growth of and Reduce the Cadmium and Lead Content in the Subsequent Maize

Arbuscular mycorrhizal fungi (AMF) are widely present in heavy metal-polluted soils, but their effects on straw degradation and plant growth of rotated crops are poorly understood. In this study, a pot experiment was used to simulate the return of fore-rotating crop (Brassica napus L.) straw to farmland with a subsequent planting of maize in a lead–zinc mining area on the Yunnan Plateau, Southwest China, which included four treatments: control (CK), addition of rape straw (SR), inoculation of AMF (AMF), and both AMF inoculation and straw addition (AMF + SR). The effects of AMF on the degradation and nutrient release of the fore-rotating rape straw and the growth, mineral nutrition and the cadmium (Cd) and lead (Pb) contents of the subsequent maize were investigated. Compared with the CK treatment, AMF significantly promoted the degradation of rape straw and the release of mineral nutrients (nitrogen, phosphorus and potassium) as well as the Cd and Pb, increased the content of available nutrients in soil, and improved the mineral nutrient contents in the maize. AMF + SR significantly increased the maize height and biomass by 32–35% and decreased the available Cd and Pb contents in soil and the Cd and Pb contents in the maize by 20–30% and 18–25%, respectively. Moreover, the available Cd and Pb contents in the soil presented significant positive correlations with their contents in the maize but negative correlations with the height and biomass of the maize. Thus, AMF played an important regulatory role in the nutrient cycling and heavy metal accumulation of the crop rotation.

Re-Mining of Waste Rock Dumps from a Closed Lead–Zinc Mine—Characterisation of the Residuals

The lead–zinc mine Bleiberg-Kreuth located in the Austrian federal state of Carinthia has had a long mining history, spanning from the early 14th century to the 1990s. The mining and processing activities undertaken over the centuries and, consequently, the composition of the waste rock material changed throughout this period. Today, the focus on waste rock dumps is motivated firstly by environmental interests and secondly by economic aspects. This article provides a comprehensive approach for the characterisation of three different waste rock dumps. The characterisation covers both mineralogical–geological methods and those involving the use of a mineral processor. The characterisation method presented herein starts with the sampling and calculation of the sampling mass, followed by sieve analysis and sink–float analysis, resulting in a two-dimensional fractional analysis. The consolidated results of the fractional and chemical analyses allow for a simplified forecast model for an ideal classification and density separation. Finally, the practical processability of a pre-concentration was tested by trials for comminution, classification, and density sorting.

Effect of Lead–Zinc Mining on Socio-Economic and Health Conditions of Enyigba and Ishiagu Lead–zinc Mining Districts of Southeastern Nigeria

Effect of Lead–Zinc Mining on Socio-Economic and Health Conditions of Enyigba and Ishiagu Lead–zinc Mining Districts of Southeastern Nigeria

Trace metal element pollution in media from the abandoned Pb and Zn mine of Lakhouat, Northern Tunisia

This study aimed to determine the contamination status, dispersion mechanisms, and ecological and health risks associated with trace elements in environmental media collected from the abandoned lead and zinc mine of Lakhouat, Northern Tunisia. A total of 41 samples, including 3 mine tailings, 21 stream sediments and 17 soils were collected and analysed for some potentially toxic elements (As, Pb, Hg, Cd, Cr, Co, Ni, Cu, Zn and Zr). Among 10 potentially toxic elements that were analysed, As, Cd, Hg, Pb and Zn exhibited considerably high concentrations in mine tailings and stream sediments. The Spearman rho correlation coefficient and principal component analysis showed that mining activities mainly controlled As, Cd, Hg, Pb and Zn. At the same time, natural sources strongly governed Co, Cr, Cu, Ni and Zr. Pollution indices revealed a very contaminated area with an essential risk to ecosystems and human health. Ecological risk assessment suggested that the potentially toxic elements in mine tailings and stream sediments induced significant ecological risks, mainly mediated by Cd. The health risk assessment revealed that oral ingestion was the primary exposure pathway to potentially toxic elements in the stream sediments and mine tailings, and children were more susceptible to adverse health effects. Pb and As had high non-carcinogenic risks for an individual potentially toxic element, and Cd and As presented intolerable carcinogenic risks. Overall, the results indicated the need for epidemiological studies to outline the extent of the occurrence of diseases related to mining activities in the region.

Effect of past century mining activities on sediment properties and toxicity to freshwater organisms in northern Sweden

The release of toxic metals from local mining activities often represents a severe environmental hazard for nearby lake ecosystems. Previous studies on the impact of mining have primarily focused on single lakes, with less emphasis on spatial and temporal recovery patterns of multiple lakes within the same catchment, but with different hydrological connection and distance to the pollutant source. This knowledge gap prevents us from assessing the real environmental risk of abandoned mines and understanding ecosystem recovery. This study explores the intensity and spatial patterns of sediment contamination and the potential for ecosystem recovery in three lakes in close vicinity of a lead (Pb) and zinc (Zn) mine in Sweden that has been inoperative for >20 years. Dated (210Pb and 137Cs) sediment cores from each lake were used to reconstruct temporal patterns in trace element deposition and relate those with past mining activities. Results show that all lakes were affected by mining, indicated by increasing Pb and Zn concentrations and decreasing organic matter content, at the onset of mining. However, the extent and timing of mining impact differed between lakes, which was partly ascribed to differences in the historical use of tailings and settling ponds. Assessment of toxicity levels in sediments, based on normalized Probable Effect Concentration Quotient (PEC-Q) to organic matter content, provided more consistent results with the historical mining than conventional methods, showing a decreasing impact in lakes once the operations ceased. Still, sediment Pb concentrations were > 10 times higher than pre-mining values, evidencing the urgent need for remediation actions in the study lakes. This study highlights the importance of considering spatial heterogeneity in metal deposition, sediment organic matter content, and hydrological connectivity with tailings when risk assessments are performed in mining-impacted lakes. The use of normalized PEC-Q in toxic assessments is also recommended.