Release Of Metals Research Articles

Green synthesis of carbon dots for sensing of heavy metal ions: Bibliometric analysis from 2003-2024

The release of heavy metals into the environment has surged, due to rapid industrialization and urbanization globally, which causes. contamination of air, water, and soil. These persistent and bioaccumulative metals (lead, mercury, cadmium, and arsenic) pose major risks to both human health and the ecological balance. Therefore, heavy metal pollution emerges as a daunting challenge in contemporary times, Carbon dots (CDs) have attracted significant attention in recent years due to their potential applications in sensing heavy metal ions. Many conventional chemical methods have been used for the synthesis of CDs, however, these methods possess many shortcomings such as noxious byproducts, harsh chemicals, high cost, etc. To diminish these shortcomings, green chemistry plays a significant role in the preparation of CDs. Thus, it is very imperative to explore the green synthesis methodologies for the preparation of CDs over conventional ones. The article delves into a comprehensive bibliometric analysis of the green synthesis methods CDs for heavy metal ion sensing applications in the period between 2003-2024. Additionally, we have also provided an overview of the mechanism behind the green synthesis of CDs by exploring the role of phytoconstitutes present in natural resources. Furthermore, the sensing mechanism of CDs toward heavy metal ions is also explored. This review compiles the bibliometric analysis and synthesis process with various materials used for the detection of heavy metals.

Antioxidant response to ZnO nanoparticles in juvenile Takifugu obscurus: protective effects of salinity.

The extensive utilization of Zinc Oxide nanoparticles (ZnO NPs) has garnered significant attention due to their detrimental impacts on ecosystem. Unfortunately, ecotoxicity of ZnO NPs in coastal waters with fluctuating salinity has been disregarded. This study mainly discussed the toxic effects of ZnO NPs on species inhabiting the transition zones between freshwater and brackish water, who are of great ecological and economic importance among fish. To serve as the model organism, Takifugu obscurus, a juvenile euryhaline fish, was exposed to different ZnO NPs concentrations (0-200 mg/L) and salinity levels (0 and 15 ppt). The results showed that a moderate increase in salinity (15 ppt) could alleviate the toxic effect of ZnO NPs, as evidenced by improved survival rates. The integrated biomarker response index on oxidative stress also revealed that the toxicity of ZnO NPs was higher in freshwater compared to brackish water. These outcomes can be attributed to higher salinity (15 ppt) reducing the bioavailability of ZnO NPs by facilitating their aggregation and inhibiting the release of metal ions. It is noteworthy that elevated salinity was found to alleviate ZnO NPs toxicity by means of osmotic adjustment via the activation of Na+/K+-ATPase activity. This study demonstrates the salinity-dependent effect of ZnO NPs on T. obscurus, suggesting the possibility for euryhaline fish like T. obscurus to adapt their habitat towards more saline environments, under constant exposure to ZnO NPs.

Innovative wound management: creating dynamic Alg-Mg/SF hydrogels for controlled Mg2+ release in wound healing.

Antibacterial hydrogels have gained considerable attention for soft tissue repair, particularly in preventing infections associated with wound healing. However, developing an antibacterial hydrogel that simultaneously possesses excellent cell affinity and controlled release of metal ions remains challenging. This study introduces an antibacterial hydrogel based on alginate modified with bisphosphonate, forming a coordination complex with magnesium ions. The hydrogel, through an interpenetrating network with silk fibroin, effectively controls the release of magnesium ions and enhances strain resistance. The Alg-Mg/SF hydrogel not only demonstrates outstanding biocompatibility and broad-spectrum antibacterial properties but also stimulates macrophages to secrete anti-inflammatory factors. This advanced Alg-Mg/SF hydrogel provides a convenient therapeutic approach for chronic wound management, showcasing its potential applications in wound healing and other relevant biomedical fields.

Effect of Loading Frequency on the Fretting-Corrosion Degradation of the Stem-Head and Stem-Cement Interfaces in Hip Implants

Abstract Degradation by fretting-corrosion of the stem-head interface is considered the main source of the release of metal ions and debris, leading to adverse tissue reactions at the cemented total hip arthroplasty. The aim of this study was to investigate the effect of loading frequency on the fretting-corrosion degradation at the stem-head and stem-cement interfaces through electrochemical measurements during the benchtop testing. Different loading frequency conditions were investigated with the same number of cycles (1,000 cycles) to calculate the fretting current and Faraday mass loss. For both interfaces, there was a biphasic waveform response of the fretting current to the load applied, at 1 Hz, almost with phase opposition. An increase in the loading frequency (1 to 30 Hz) generated a higher fretting current for the stem-head (2.97 ± 2.04 μA to 7.66 ± 2.46 μA) and stem-cement (7.62 ± 2.26 μA to 25.48 ± 5.35 μA) interfaces. However, an increase in the loading frequency (1 to 30 Hz) reduced the Faraday mass loss of the stem-head (0.79 ± 0.54 μg to 0.07 ± 0.02 μg) and stem-cement (2.02 ± 0.62 μg to 0.32 ± 0.12 μg) interfaces because of a reduction in the overall testing time. Thus, there is a compromise relation between the fretting current and the Faraday mass loss, which must be considered when setting the loading frequencies in the fretting-corrosion benchtop testing of hip implants.

Influence of aluminum incorporation and aqueous conditions on metal ion release of high-Ni transition metal oxide nanomaterials

Developing a materials perspective of how to control the degradation and negative impact of complex metal oxides requires an integrated understanding of how these nanomaterials transform in the environment and interact with biological systems.

The endocrine disruptor effect of metal nanoparticles mainly depends on their capacity to release metal ions

The endocrine disruptor effect of metal nanoparticles mainly depends on their capacity to release metal ions

Microbial Community with Potential for Metal Release Isolated from Palca Mine Tailings Pond in Peru

Microbial Community with Potential for Metal Release Isolated from Palca Mine Tailings Pond in Peru

Removal of Copper (II) from Mining Waste Water by Adsorption onto Activated Carbons Produced from Hazelnut Shell

Mining wastewater is one of the most important environmental problems today because of the heavy metal ions they contain. Wastewaters containing heavy metal pollution are generally acidic waters with low BOI (Biochemical oxygen demand) value. Various processes such as mineral processing waste disposal, illegal mining, domestic waste disposal, and others result in the release of heavy metals into the waters. One of the heavy metals that cause problems in terms of environmental pollution is copper. Copper metal is commonly found in metal and metal plating industry wastewater. Although metal industry wastewater is low in quantity, they are toxic waste. For this reason, industrial wastewater must be treated before being discharged into the receiving environment. In this study, the amount of Cu in wastewater of the mining operation in Gümüşhane was determined. Heavy metal pollution was eliminated with an adsorbent produced from agricultural biowaste. It has been tried to determine the amount of adsorbent, contact time, and treatment efficiency of wastewater at different pHs of activated carbon produced by chemical activation. As a result, an average of 88.7% efficiency was obtained with activated carbon activated with KOH, while 22,4% copper removal efficiencies were obtained with raw material (hazelnut shell) used without activation. It was determined that the appropriate working pH was 5,0; the amount of adsorbent was 0.05 g and Qmax 121,2. As a result, in this study, very low-cost adsorbents were produced using waste hazelnut shells, and a biotechnological approach was proposed to clean copper-containing wastewater.

A review of toxicity assessment procedures of solar photovoltaic modules

Environmental management of solar photovoltaic (PV) modules is attracting attention as a growing number of field-operated PV modules approach end of life (EoL). PV modules may contain small amounts of toxic metals, and the procedures for assessing and regulating the toxic metal content and release of such materials at EoL differ widely across nations. This paper provides an overview of the metal composition of PV modules and common procedures for toxicity assessment through extensive research and review of technical literature and legislative documents. This review focuses on three primary aspects: first, it explores the distribution of toxic elements within current and emerging PV module designs, with a specific focus on obtaining representative samples for proportional toxicity testing within different module laminate areas. Second, it examines a sampling standard and the diverse toxicity testing methods and regulations employed in various regions, encompassing standards like the Environmental Protection Agency (EPA) Test Method 1311 (Toxicity Characteristic Leaching Procedure, TCLP) in the U.S., Restriction of Hazardous Substances (RoHS) in Europe, and the Waste Extraction Test (WET) in California. Third, the review examines the sources of variability in toxicity testing outcomes, including techniques for securing homogeneous samples from non-uniform PV modules, selecting particle sizes representative of landfill conditions in extracted samples, determining appropriate leachate characteristics such as leaching agents and pH levels, and considering factors like test duration and temperatures. In summary, this review summarizes relevant regulations and offers a comprehensive overview of the strengths and limitations associated with several toxicity assessment procedures currently in practice.

A nationwide investigation on the characteristics and health risk of trace elements in surface water across China

Rapid urbanization accelerates the release of anthropogenic heavy metals from local to wider water systems, posing a serious threat to aquatic ecosystems and public health. The characteristics of trace elements were investigated to evaluate the environmental status of surface water in 40 cities of China. The concentrations of 22 elements in surface water ranged from 7.00 × 10−4 to 4.37 × 105 μg/L. The water quality can be classified as “excellent” except Songhuajiang. The levels of As, Cd, Cr, Pb, and Hg are all within the limits permitted by national drinking water quality standards. An obvious regional distribution characteristic was observed, with concentrations of Zn, Mn, Ni, Cu, Co, U, and Cr higher in surface water collected in the north than in the south, while the trends for Cd, Tl, and As are opposite. Notably, Tl shows significant geographical divergences, with the level of surface water collected from the south nine times higher than that from the north. The regional distribution of the mineral, industrial, or agricultural activity might be responsible for the south-to-north difference of these elements. The hazard index (HI) and total cancer risk (TCR) through oral or dermal contact with water-related heavy metals were further calculated. The average HI was 0.54 in the north and 0.29 in the south for adults, while HI for children was relatively higher. The value was 1.01 and 0.55 in the north and south, respectively. TCR in the north is 2.58 × 10−4 and mainly contributed by Cr (88.1 %), while TCR in the south is 4.48 × 10−5 and mainly contributed by As (98.4 %). The research results can provide essential data for effective water resources management and human health protection in China.

Ceramic-on-Metal Bearing in Total Hip Arthroplasty—Was It So Bad? A Narrative Review and a Critical Analysis of the Literature

Hip replacement has significantly improved the quality of life of patients with symptomatic hip osteoarthritis. Various bearings have been developed over the years. Each of these has advantages and disadvantages. On the one hand, Metal-on-Metal (MoM) has been associated with a high level of wear and metal ion release of chromium (Cr) and cobalt (Co). On the other hand, Ceramic-on-Ceramic (CoC) bearings, known to have a wear rate close to zero, have been associated with an increased risk of squeaking and component fracture. Ceramic-on-Metal (CoM), a hybrid hard-on-hard bearing, was proposed to overcome the CoC and MoM limits. Preliminary clinical and radiographical results have been described as favourable. Due to the failure of MoM and the increased risk of ion release and metal toxicity, CoM was withdrawn from the market without causing significant clinical complications. Data from the literature showed that CoM bearings are reliable and safe at medium- and long-term follow-up, if correctly implanted. In this narrative review, we analysed the real risks and benefits associated with the implantation of CoM bearings.

Cu ions release and the formation of CuO/Cu2O during PEO based on the work function

The Cu ions release was investigated by the work function by scanning kelvin probe (SKP), and the formation of CuO/Cu2O was also researched by recording plasma discharges during plasma electrolytic oxidation (PEO) of Ti-14Cu alloy with different morphologies Ti2Cu phase. It is found that L-Ti2Cu phases with lower work function enhances the escape of Cu valence electrons from the 4 s energy level more easily compared to the G-Ti2Cu and GL-Ti2Cu phases. Consequently, this leads to earlier Cu ions released from L-Ti2Cu phases as opposed to the G-Ti2Cu and GL-Ti2Cu phases. The earlier Cu+ released from L-Ti2Cu phases increases the formation of Cu2O and further oxidizes into CuO with increasing voltage, which lead to the enhanced the relative content of CuO. This enhancement contributes to improving antibacterial activity and tribocorrosion resistance due to stress response and lubrication effect by high relative content of CuO. This research provides a theoretical reference for the metal ions release of Ti-14Cu alloy in oxidation dissolution process of PEO and the formation of corresponding metal oxides.

Assessment of in-vivo corrosion of Ti and CoCrMo joint implants by electrochemical measurements in human synovial liquids

Understanding the corrosion behavior of biomedical materials in the human body is an essential step for the development of improved materials and clinical procedures in arthroplasty. In this work, the corrosion behavior of Ti and CoCrMo alloys in human synovial fluids directly extracted from patients was investigated through an electrochemical experimental protocol, including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The results show that the corrosion behavior of both materials largely depends on patients. The obtained corrosion rates of both materials correspond well to the metal ion release rate detected in patients with joint implants revealing the adequateness of the electrochemical experimental protocol for quantifying in-vivo corrosion of biomedical implants. Based on the results, no significant risk of galvanic corrosion of Ti/CoCrMo coupling is anticipated. The rates of wear-accelerated corrosion (one of the main degradation mechanisms of metallic artificial hip joints) were theoretically extracted from the present electrochemical measurements using an established tribocorrosion model. Those material loss rates are patient-dependent and can be up to two orders of magnitude higher than the static corrosion rates, indicating that the nature of the patient can critically affect the degradation rate of the joint implant.

(Invited) Electrochemically Driven Ion-Exchange Remediation of Water Containing High Fluoride Content

Remediation of water contaminated by anthropogenic activities is required to provide clean water for human consumption and prevent damage to the environment. The scale of the challenge is signaled by its inclusion in the UN 17 Sustainable Development Goals [1]. Major contributors to the problem are industrial activity and agriculture. The former commonly results in the release of metals; analysis and separation of such cationic species have received considerable attention [2]. In the latter instance, run-off of fertilizers used to enhance crop yields can result in unacceptable levels of nitrate or phosphate in natural waters. While monitoring of anionic species is widely undertaken using ion selective electrodes [3], the promise of electrochemical separation technologies [4] in this area is less well developed.For anthropogenic causes, remediation is the last resort following failure to prevent release of toxic materials into the environment. In contrast, there are instances where the “contaminant” is natural: fluoride is a prime example. The beneficial dental health effects of fluoride are widely appreciated, but excessive amounts are harmful to teeth, bones and various organs [5]. The World Health Organization (WHO) identifies the optimum fluoride level in drinking water to be 0.5-1.0 mg/L. In many regions, water is fluoridated to realize the health benefits. However, local geological conditions many countries can result in natural water fluoride levels significantly above the recommended upper limit of 1.5 mg/L.This presentation addresses the challenges associated with remediation of anions, with particular focus on fluoride. At the outset, it is recognized that for potable water the requirement is not full de-ionization but selective removal of contaminants: this is a separation challenge. The attributes, performance and potential for scale-up of a range of (electro)chemical remediation strategies will be discussed in general. We then focus on electrochemically switched ion-exchange (ESIX) [6], for which application to water softening [7] and perchlorate removal [8] has been demonstrated.We explore the facility of aniline-based (co-)polymer films to reversibly extract and eject fluoride ions as the charge (oxidation state) of the films are subject to electrochemical control. Homopolymer and copolymer films based on aniline, o-aminophenol and o-toluidine were deposited potentiodynamically. Film thickness was controlled via the number of potential cycles: the resultant electroactive site population was assayed coulometrically in monomer-free background electrolyte. Film mass was assayed gravimetrically using the EQCM. For relatively thin films, correlation of film mass and charge capacity revealed the solvent content. During deposition of thicker films, acoustic admittance data revealed the progressive evolution of viscoelastic effects. Co-monomer feedstock has a significant influence on film deposition rate, absolute solvent population and redox-driven solvent population change [9].The ion-exchange capacity of the films for redox-driven fluoride uptake was determined upon exposure to aqueous solutions of varying fluoride concentration, both in the absence and presence of chloride as a competing anion. EQCM mass and charge responses, respectively, provide overall “ion+solvent” and “solvent” population changes: correlation permits separation of fluoride and water uptake/release. Copolymer composition significantly influences the ease of fluoride uptake and release and reveals ion trapping. Complementary data on the dynamics of ion and solvent transfers are provided by shorter timescale experiments, involving voltammetry at faster scan rates and chronoamperometry. Correlation of gravimetric and coulometric data permits temporal separation of fluoride and solvent entry and exit.Practical exploitation of these promising fundamental observations will require scale-up and optimization of cycle life, film viscoelasticity and response time as functions of film thickness. We speculate that spatially variant film solvation will be a critical parameter. To this end, we consider the viability of neutron reflectivity measurements with isotopic substitution to determine the spatial distributions of fluoride and solvent in films of graded composition.

Heterogeneous Capture and Release of Energy Metals Using Carborane-Tethered Electrodes

Li and U are the only trace metals dissolved in seawater that are proposed to be economical to extract. Both are at very low concentrations (Li (0.17 ppm), U (3.3 ppb)); however, their total content are approximately 10,000 and 1,000 times higher than in land-based reserves, respectively, representing huge untapped resources which could be collected in an environmentally friendly manner. With surging demand for Li-ion batteries for energy storage, it is estimated that current production methods will soon not meet market demands. In addition, low-carbon nuclear energy production is also expected to increase dramatically in many major countries.Previous studies have shown that reduction of the substituted closo-carborane polyhedral cluster, 1,2-L2-C2B10H10, to the nido-carborane, [1,2-L2-C2B10H10]2-, resulted in the rupture of the C–C bond, cage opening, and an increased bite angle, Θ (Scheme). This talk will start by describing how we used this redox-controlled chelation for the selective electrochemical capture and release of UO2 2+ from mixed-metal mixtures mimicking spent nuclear fuel in monophasic and biphasic media (Scheme; M = UO2 2+; L = Ph2PO).1-2 We will then discuss our current efforts to target other metals of energy importance, in particular M = Li+, for seawater extraction by incorporating Li-selective donating groups, L (Scheme). This talk will then focus heavily on our current work on anchoring these carboranes onto electrode surfaces using anchoring groups – e.g., allyl, pyrene, or thiols – for heterogeneous capture and release using galvanostatic charge/discharge cycles. Recent, soon-to-be published results demonstrate the successful application of this redox-controlled chelation for heterogeneous, selective capture of UO2 2+ from mixed-metal mixtures. Keener, M.; Hunt, C.; Carroll, T. G.; Kampel, V.; Dobrovetsky, R.; Hayton, T. W.; Ménard, G. Redox-switchable carboranes for uranium capture and release. Nature 2020, 577, 652-655.Keener, M.; Mattejat, M.; Zheng, S.-L.; Wu, G.; Hayton, T. W.; Ménard, G. Selective electrochemical capture and release of uranyl from aqueous alkali, lanthanide, and actinide mixtures using redox-switchable carboranes. Chem. Sci. 2022, 13, 3369-3374. Figure 1

A combinatorial hollow cathode discharge/plasma polymerization system for silver containing plasma parylene coating

The conventional pyrolysis of parylene coating depends on a high vacuum environment and an expensive solid dimer precursor. Our previous study successfully demonstrated the feasibility of synthesizing plasma parylene (PP) coating using plasma polymerization with a liquid para-xylene precursor. The deposition conditions for plasma polymerization are compatible with the vacuum level of the hollow cathode discharge (HCD). This led to the idea of using an HCD gun as the metal source to incorporate metal into the plasma polymerized films, thereby achieving different coating functions and extending applications, such as active antibacterial purposes. In this study, an HCD gun was installed on the plasma polymerization reactor to synthesize a silver containing plasma parylene (Ag-PP) coating, where the silver HCD tube serves as the in situ source for incorporating silver.The experimental results demonstrate that the quantity of incorporated silver increases linearly with the power delivery level of the HCD device, and its content can be controlled during deposition to form an Ag-PP coating. Microstructural analysis reveals that the incorporated silver exhibits a crystalline and granular structure with a metallic state in the Ag-PP coating. Furthermore, the Ag-PP coating significantly resists both Staphylococcus aureus and Escherichia coli, with an antibacterial activity value exceeding 2.0 after 24 h of plate culture, corresponding to a silver metal ion release of 2–3 ppb. This quantitatively substantiates that the incorporated silver can impart an active antibacterial function to the PP coating for biomedical surface treatment applications.

Complex Speciation and Distribution of Iron, Sulfur, and Trace Metals in Coal Mine Soils Reflect Grain- and Sub-Grain-Scale Heterogeneity during Pyrite Oxidative Dissolution

Historical coal mining practices have caused various soil and water hazards, particularly through the dumping of mine waste. The primary environmental risk associated with this waste is the leaching of toxic metals from dumps of spoil or refuse into the subsurface soil or into nearby water resources. The extent of metal release is controlled via the oxidative dissolution of pyrite and potential re-sequestration through secondary Fe oxides. The characterization of the dominant Fe-bearing phase and the distribution of trace metals associated with these phases was determined via electron microscopy, synchrotron-based X-ray micro-fluorescence (μ-XRF) element and redox mapping from shallow mine soils from an impacted watershed in Appalachian Ohio. The dominant Fe-bearing phases were: (1) unweathered to partially weathered pyrite; (2) pseudomorphic replacement of pyrite with Fe(III) oxides; (3) fine-grained Fe oxide surface coatings; and (4) discrete Fe(III) oxide grains. Thicker secondary coatings and larger particles were sulfate rich, whereas smaller grains and thinner coatings were sulfate poor. The discrete Fe oxide grains exhibited the highest concentrations of Cr, Mn, Ni, and Cu, and sub-grain-scale concentration trends (Mn > Cr > Ni > Cu) were consistent with bulk soil properties. Predicting future metal transport requires an understanding of metal speciation and distribution from the sub-grain scale to the pedon scale.

Mesophilic, thermophilic and thermal hydrolysis process coupled anaerobic digestion of sewage sludge: Biomethane potential, pathogen removal and energy feasibility

Conventional Anaerobic digestion is one of the most preferred sludge management techniques however, it has limitations such as low hydrolysis rate, longer retention time, larger digester volume, and reduced methane generation etc., To overcome these problems, Thermal hydrolysis process (THP) has been used as an effective pretreatment method for enhancing methane generation. However, the effect of the thermal hydrolysis process in heavy metal solubilization and methane production from high SRT (solids retention time) sludge is still not clear. Anaerobic digestion of sewage sludge sourced from sequencing batch reactor (SBR) and conventional activated sludge process (CASP) systems were evaluated under mesophilic (MAD), thermophilic (TAD), and thermal hydrolysis process (THP) mediated anaerobic digestion (AD) in terms of methane generation and, VS and pathogen removal. THP resulted in almost 38% COD solubilization for SBR and CASP sludge. Anaerobic digestion of SBR sludge resulted in methane generation of 101, 166, and 390 mL/gVS under mesophilic, thermophilic, and THP pretreatment conditions, respectively. For CASP sludge, the highest methane generation was observed for THP pretreated sludge (587 mL/gVS), followed by thermophilic (298 mL/gVS) and mesophilic digestion (241 mL/gVS). The fecal coliforms in the mesophilic and thermophilic digested SBR sludge were 3000 and 620 MPN/g, respectively, while 6100 and 740 MPN/g were found in digested CASP sludge, respectively. The THP-MAD and TAD processed SBR, and CASP sludges met the Class A sludge fecal coliforms and Salmonella density criteria of <1000 MPN/g TS (dry basis) and 3 MPN/4g TS (dry basis), respectively, over MAD processed sludges. Even though THP pretreatment resulted in the release of heavy metals, the concentration of heavy metals in the THP effluent was lesser than the limits prescribed by USEPA. The energy demand of the THP unit (160 °C, 6 bar) was estimated to be 162 MJ/m3. The energy balance analysis revealed that THP pretreatment would lead to energy self-sufficiency upon integration in a wastewater treatment plant (WWTP). This study can provide an experimental basis to apply THP pretreatment to enhance hydrolysis rate in anaerobic digesters while maximizing methane production and achieving energy benefits over MAD and TAD.

Mineralogical fingerprint and human health risk from potentially toxic elements of Fe mining tailings from the Fundão dam

In 2015, >50 million cubic meters of Fe mining tailings were released into the Doce River basin from the Fundão dam, raising the question of its consequences on the affected ecosystems. This study aimed to establish a mineralogical-(geo)chemical association of potentially toxic elements (PTEs) from Fe mining tailings from the Fundão dam, collected seven days after the failure, through a multidisciplinary approach combining assessment of the risk to human health, environmental geochemistry, and mineralogy. Thus, eleven tailings samples were collected with the support of the Brazilian Military Police Fire Department. Granulometry, magnetic measurements, optical microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and sequential chemical extraction of PTEs analyses were performed. Contamination indexes, assessment of risk to human health, and Pearson correlation were calculated using the results of sequential chemical extraction of PTEs. The predominance of goethite in Fe oxyhydroxide concentrates from the mud indicates that the major source of hematite may not be from tailings, but from pre-existing soils and sediments, and/or preferential dissolution of hematite in deep flooded zones of the tailings column of the Fundão dam. Moreover, the high correlation of most carcinogenic PTEs with their crystallographic variables indicates that goethite is the primary source of contaminants. Goethites from Fe mining tailings showed high specific surface area and Al-substitution, and due to their greater stability and reactivity, the impacts on PTE sorption phenomena and bioavailability may be maintained for long periods. However, their lower dissolution rate, and the consequent release of heavy metals would promote greater resilience for affected ecosystems, preventing significant PTE inputs under periodic reduction conditions. More specific studies, involving the crystallographic characteristics of Fe oxyhydroxides should be developed since they may provide another critical component of this set of complex and dynamic variables that interfere with the bioavailability of metals in ecosystems.

The gravel pit lakes’ water quality, their aquatic ecosystem function, and the effects of environmental changes in northern Poland

Water quality is an important factor to determine a development of living organisms, including the presence of amphibians. It this article we compared the water quality of both, natural infield reservoirs in areas with intensive cultivation of cereals and the recently created reservoirs in the gravel pits in Central Pomerania, northern Poland. We tested all the physico-chemical properties that may impact species richness and reproductive success of amphibians. We observed that gravel ponds were better oxygenated, with higher pH and conductivity, and were less fertile in nutrients. In Pomerania, the water reservoirs in gravel pits had better breeding conditions than in-field ponds with higher total nitrogen and total phosphorus concentrations. There are many scientific papers identifying a negative role of sand and gravel mines, including a release of heavy metals from sediments, a high non-metalic minerals concentration, a destruction of native species of vegetation and occurrence of alien species. Therefore, we should be careful in assessing the role of newly emerging reservoirs in sand and gravel mines. The purpose of our research is to show that sand/gravel mines can be used to protect nature and that they can have also a positive impact. Few previous studies indicate that they may be a favorable place for creating new breeding sites for amphibians, which may ultimately help to preserve species in the face of environmental pollution and climate change.