Enrichment Of Cu Research Articles

Microstructure and Precipitation of a Cu–Ni Alloyed Medium‐Mn Duplex Low‐Density Steel Prepared by Near‐Rapid Solidification

A Cu–Ni‐alloyed medium‐Mn duplex low‐density steel with a composition of Fe–9Mn–5.5Al–0.3C–3Ni–1.5Cu (wt%) is prepared by near‐rapid solidification. The microstructure features of the alloy under as‐cast, cold‐rolling, and heat treatments are studied. The effect of Cu‐ and Ni‐alloying elements on the microstructure and precipitates is discussed. In the results, it is shown that martensite and nanoscale precipitates are found in the microstructure of near‐rapid solidification. The enrichment of Cu is found at the phase boundaries of austenite and ferrite. A large number of annealing twins are present in the microstructure of cold‐rolled and annealed alloy. In the first principles and thermodynamic calculations, it is shown that Ni element is capable to shorten the nucleation incubation time of Cu precipitates. In addition, the interface segregation of Ni and Al elements reduces the adhesion work of Cu particles with the matrix. Both Cu and Ni elements increase the stacking fault energy of the alloy, which is increased from 37.3 to 44.2 mJ m−2. The contributions of precipitation strengthening and twinning strengthening to the strength of the alloy are 72 and 86 MPa, respectively, while the dominant contribution of dislocation hardening to the strength is 326 MPa.

Effect of micro-nano hybrid SiCp on microstructure and mechanical properties of 7075Al alloy

In this study, micro-nano hybrid SiCp/7075Al composites were successfully prepared for the first time by ultrasonic-assisted semi-solid stirring casting method. The effects of micro-nano hybrid SiCp on the microstructure and mechanical properties of 7075 Al were studied. The results show that the distribution of SiCnp and micron SiCp in the microstructure was uniform. During the extrusion process, most of the micron SiCp were subjected to significant load and broken, which increased the contact area with the matrix and promoted the interface bonding. In addition, the enhanced interfacial interaction promoted the formation of MgAl2O4 phase, which significantly improved the mechanical properties. SiCnp not only had a significant effect on grain refinement, but also promoted the enrichment of Cu, accelerated the formation of GP zone, and promoted the formation of more nano-MgZn2 precipitates. The yield strength and the elastic modulus of micro-nano hybrid SiCp/7075 Al composites reached 450 MPa and 94 GPa, respectively. The synergistic effect of SiCnp and micron SiCp could produce composite strengthening effects such as load transfer strengthening, thermal mismatch strengthening and Orowan strengthening. Moreover, a large number of dislocation pile-ups were observed near the interface between micron and nano SiCp and Al matrix. This leaded to a higher work hardening rate of the composites as the particle content increases. The higher work hardening rate enhanced the strain hardening ability of the material during plastic deformation, thereby significantly improving the tensile strength and elongation of the material.

Transport and Mobilization of Trace Elements from Tailings and Other Mining Waste, in the Arid Environment of the Mojave Desert, California, USA

ABSTRACT Mining activities can lead to an exacerbated enrichment of metal concentrations. Pollution by metal(loid)s in arid regions has been little elucidated. This study assessed the transport and mobilization of trace elements in an arid environment under two ephemeral wash systems originating from processed tailing materials in the Valley Wells Smelter, California (USA). Overall, enrichment factors evidence a significant increase in trace elements in the South Wash compared to the North Wash. The Principal Component Analysis demonstrates in the South Wash that Cd-Cu is associated with As-Pb-Zn and Ba-Co-Mn primarily. All areas (from South and North wash) indicated extremely high enrichment of Cu due to mining activities. Data showed that in the northern wash area the metals As, Cu and Sr presented concentrations much higher than the background. The geochemical survey indicates deleterious effects on the environmental quality of the investigated areas, requiring reparative and conservative measures.

In-situ geochemical and isotopic analyses of multiple pyrite generations: Insights for the giant Beiya Au polymetallic ore genesis in southwestern China

The Beiya giant Au polymetallic deposit is located in the Sanjiang Tethyan Orogen, northwestern Yunnan (SW China). The ores occur as disseminations or veinlets in granite porphyry. To unravel the ore genesis at Beiya, we analyzed the ore-related sulfide trace elements and sulfur isotopes. Py-1 is mainly euhedral-subhedral medium-/coarse-grained (size: > 100 μm), with relatively smooth surface and some pores. Py-2 is mostly coarse grained (size: 50–200 μm), with well-developed pores and inclusions. The pyrite is usually Co-Cu rich and V-Ti-Sb poor, resembling typical magmatic-hydrothermal pyrite. In addition, the Co/Ni ratios decrease from pyrite-1 (Py-1) to pyrite-2b (Py-2b), suggesting that their chemical compositions are controlled by magma fractionation. We found that Co, Ni, As, and Se occurred as solid solution in the pyrite lattice, while Pb, Bi, Ag, and Mn occurred mainly in inclusions in the pyrite. Pb and Bi display good positive correlation, suggesting that they occurred as inclusions or nano-particles in pyrite lattice. The pyrite samples have sulfur isotope value (δ34S) of 0.62–3.45 ‰ (avg. 2.35 ‰) for Py-1, 0.18–3.12 ‰ (avg. 1.85 ‰) for Py-2a, and 0.62–4.18 ‰ (avg. 2.51 ‰) for Py-2b. These characteristics may have played a vital role in the initial enrichment of Cu, Mo, Au, and ultimately formed the complex polymetallic system at Beiya.

Amphibole geochemistry in the Haobugao skarn Zn-Fe-Sn deposit in the southern Great Xing’an Range: Implications for the ore-forming process

The Haobugao Zn-Fe-Sn deposit is a typical skarn deposit in the southern Great Xing’an Range of NE China. Despite many advances in understanding its genesis, the detailed ore-forming processes of Zn, Fe and Sn are still unclear. Amphibole, a rock-forming mineral, has been well studied as an indicator of diverse magmatic and metamorphic processes; however, the geochemistry of hydrothermal amphibole has previously received less attention. The Haobugao deposit contains two generations of hydrothermal amphibole (Amp-I and Amp-Ⅱ), which provides a good opportunity to use amphibole geochemistry to trace the mineralization process. Early Amp-I coexists with cassiterite, magnetite and quartz, whereas late Amp-II coexists with quartz and sulfides and can be further divided into two subgroups: Amp-Ⅱa (in skarn) and Amp-Ⅱb (in the country rocks of siltstone). The oxygen isotopic compositions of the fluid (δ18Ofluid 2.9‰) responsible for the Amp-I formation indicate that the amphiboles formed from mixed magmatic fluid with meteoric water. Amp-I is LREE-depleted and HREE-enriched with obvious negative Eu anomalies. Amp-Ⅱ is generally slightly LREE-depleted with negative or positive Eu anomalies and positive Ce anomalies. The incorporation of trace and rare elements is mainly controlled by the fluid composition. Detailed petrological observations and amphibole geochemistry, combined with previous research results, confirm that Sn, Fe, Pb and Zn mineralization occurred during a single mineralization event. From the oxide to the quartz sulfide stage, the ore-forming fluid evolved from high-temperature and oxidized conditions with enrichment of Sn, Li, Be and REEs to low-temperature and reduced or oxidized conditions with enrichment of Cu, Co and Zn. The concentrations of Cu, Co and Zn in different amphiboles vary with the mineral crystallization sequence. This study shows that amphibole geochemistry can be useful for tracing fluid evolution and mineralization processes in hydrothermal systems.

Structure evolution of Cu3Pd single-particles under CO2 hydrogenation

Encapsulating metal nanoparticles into a porous silica shell, forming a core–shell geometry, has been popularly applied to prevent the particles from sintering at the elevated temperatures and under reactive gases. However, structure evolution of the metal particles under reaction conditions is less known. Here, the dynamic behavior of Cu3Pd single-particles, confined by a permeable silica shell, during CO2 hydrogenation have been examined by microscopic and spectroscopic characterizations. It was found that H2-reduction of the bimetallic particle at 673 K led to the partial enrichment of Cu on the surface, while H2-treatment at 873 K resulted in the surface segregation of Pd owing to the stronger adsorption of H2 on Pd. When subjected to CO2 hydrogenation at 517–673 K, the enriched Pd surface atoms and the electron-deficient Cu atoms synergistically activated H2/CO2 molecules and promoted the activity for the reverse water–gas shift. However, the Cu atoms partially migrated onto the SiO2 shell and formed tiny Cu clusters, induced by the strong adsorption of O-containing reaction intermediates, forming a core@shell@satellite (CuPd@SiO2 @Cu) architecture.

Oenothera biennis with strong copper toxicity resistance enriches trace copper in seeds under copper pollution soil

Excess copper (Cu) imparts negative effects on plant growth and productivity in soil. To develop the ability of O. biennis to govern pollution soil containing excessive Cu, we investigated seed germination, seedling growth, and seed yield. Furthermore, Cu content and the expression levels of Cu transport related genes in different tissues were measured under exogenous high concentration Cu. O. biennis seeds were sensitive to excess Cu, with an observed reduction in the germination rate, primary root length, fresh weight, and number of seeds germinated daily. Consecutive Cu stress did not cause fatal damage to evening primrose, yet it slowed down plant growth slightly by reducing the leaf water, chlorophyll, plant yield, and seed oil contents while increasing the soluble sugar, proline, malondialdehyde, and H2O2 contents. The Cu content in different organs of O. biennis was disrupted by excess Cu. In particular, the Cu content in O. biennis seeds and seed oil increased and subsequently decreased with the increase of exogenous Cu, reaching a peak under 600 mg·kg−1 consecutive Cu. Furthermore, the 4-month 900 mg·kg−1 Cu treatment did not induce the excessive accumulation of Cu in peels, seeds, and seed oil, maintaining the Cu content within the range required by the Chinese National Food Safety Standards. The treatment also resulted in an upregulation of Cu-uptake (ObCOPT5, ObZIP4, and ObYSL2) and vigorous efflux (ObHMA1) of transport genes, of which expression levels were significant positive correlation (p < 0.05) with the Cu content. Among all organs, the stem replaced the root as the organ exhibited the greatest ability to absorb and store Cu, and even the Cu transport genes could still function continuously in stem under excess Cu. This work identified a species that can tolerate high Cu content in soil while maintaining a high yield. Furthermore, the results revealed the enrichment of Cu to occur primarily in the O. biennis stem rather than the seeds and peel under excess Cu.

Ball milling coupled cascade magnetic separation to recover valuable metals from alkali disaggregation copper smelting slags

Due to the lack of effective reduction and recycling methods, copper smelting slags (CSS) containing a large number of valuable metals are stockpiled. This work proposed a novel strategy of ball milling coupled cascade magnetic separation to achieve recovery of magnetite and ferrite and enrichment of Cu and Zn in alkali disaggregation CSS. The Fe grade of recovered magnetite reached as high as 72.43%, and 15.51% of Cu and 16.63% of Zn were recovered efficiently as spinel ferrites. Simultaneously, 70.54% of Cu and 58.18% of Zn were enriched in non-magnetic fraction. Compared with primary magnetic fraction, the grade of Fe in the secondary magnetic fraction increased by 19.19%. Additionally, compared with the control, the recovery efficiency and the grade of Fe in the magnetic products after ball milling increased by 52.11% and 49.20%. The main mechanisms were as follows: (1) The significant dissociation of Fe3O4 from non-magnetic impurities and the transformation of Cu and Zn to ferrite were promoted by ball milling. (2) The separation efficiency of weak magnetic ferrite and Fe3O4 was improved by cascade magnetic separation. Therefore, the proposed strategy could provide a green and sustainable solution for CSS processing.

Effect of EDDS Application on Soil Cu/Cd Availability and Uptake/transport by Castor

To investigate the effect of chelating agents on plant uptake of heavy metals, castor (Ricinus communis L.) was used as the test plant. Soil culture and pot experiments were conducted to study the effects of different concentrations of ethylenediamine disuccinic acid (EDDS) on the forms of Cu and Cd in soil and their absorption and transport by castor. The results showed that the application of EDDS significantly increased the content of available Cu and Cd. After 15 days of cultivation, the available Cu and Cd concentrations in the soil increased by 43.01%-103.55% and 51.78%-69.43%, respectively. EDDS promoted the conversion of reducible Cu to weak acid extractable and increased the mobility of Cu. Meanwhile, the application of EDDS promoted the absorption, transport, and enrichment of Cu in castor. Under the application of 2.5 mmol·kg-1 EDDS and 5.0 mmol·kg-1 EDDS, the Cu concentrations in the shoots were 4.88 times and 16.65 times higher than that of the control (P< 0.05), and the Cu concentrations in the roots were 2.89 times and 3.60 times higher than that of the control (P< 0.05), respectively. The Cu transport coefficient significantly increased by 72.73% and 381.82% when treated with EDDS 2.5 and EDDS 5.0. Simultaneously, the phytoextraction of Cu in shoots, roots, and their sum were 14.08, 2.16, and 4.70 times higher than that of the control (P<0.05), respectively, when treated with EDDS 5.0. Furthermore, EDDS significantly increased the Cd concentrations in castor. When treated with EDDS 2.5 the shoots and roots increased by 15.15% and 57.42%, respectively, and the phytoextraction of total Cd significantly increased by 13.44%. Generally, the EDDS treatment could increase the available Cu and Cd in soil, promote the uptake of Cu and Cd, and improve the phytoremediation efficiency of castor. Among them, the addition of 5.0 mmol·kg-1 EDDS had the best effect for Cu, whereas the addition of 2.5 mmol kg-1 EDDS had a higher increase in the phytoextraction of Cd.

Underplated melts control sulfide segregation at the continental crust-mantle transition

Exposures of the Earth’s crust-mantle transition are scarce, thus, limiting our knowledge about the formation of subcontinental underplate cumulates, and their significance for metal storage and migration. Here, we investigated chalcophile metals to track sulfide crystallization within the Contact Series, an <150-m-thick pyroxenite-gabbronorite sequence, formed by mantle-derived melts, highlighting the boundary between the Balmuccia mantle peridotite and gabbronoritic Mafic Complex of the Ivrea-Verbano Zone. Within the Contact Series, numerous sulfides crystallized in response to the differentiation of mantle-derived underplated melts. Such sulfide-controlled metal differentiation resulted in anomalous Cu contents (up to ~380 ppm), compared to reference mantle (~19 ppm) and crustal samples (~1 ppm). We propose that the assimilation of continental crust material is a critical mechanism driving sulfide segregation and sulfide-controlled metal storage. Our results evidence that sulfides are trapped in the underplated mafic-ultramafic cumulates and that their enrichment in Cu may provide essential implications for crustal metallogeny.

Total and Bioaccesible Metal Concentrations in Surficial Sediment Affected by a Mining Spill: Case of Sonora River, Northwest of Mexico

ABSTRACT Metals and metalloids are persistent contaminants that are associated with many anthropogenic activities and mining in particular. On August 6, 2014, approximately 40,000 m3 of toxic acid mining waste was spilled from the Buena Vista del Cobre Copper Mine. The spill affected 220 km of the Sonora River Basin (SRB) over a surface area of ~ 30,000 km2. This study evaluated the total and bioaccessible concentrations of six metals and their enrichment in surficial sediments in spill and no-spill sites in the SRB. All metal concentrations showed significant seasonal and spatial variation (p < .05) in surficial sediments, with a general distribution of Al > Fe > Mn > Zn > Cu > Pb. The total and bioaccessible concentrations of the elements in this study were similar between spill and no-spill sites. Variations in element levels were associated with re-suspension and advection related with rain run-off, and the element concentrations were associated with the high natural concentrations in surficial sediments found throughout the SRB (considering the predominant soil types). The enrichment factor (EF) indicated minor to moderate-severe enrichment of Fe and Mn, minor to severe enrichment of Pb and Zn, and moderate-severe to very severe enrichment of Cu. The bioaccessible percentages of metals with respect to the total concentrations varied from 0.23 to 69.9%. The Sediment Quality Guidelines criteria indicated that adverse effects on biota that are mainly due to Cu levels are potentially present. Chronic exposure to metals may produce intermediate and long-term effects on the metabolic responses of biota.

Fermented rapeseed meal subjected to a biosorption process: A potential new feed additive with microelements for laying hens

The antinutritional substances contained in rapeseed play an essential role in the bioavailability of microelements contained in feed. This problem can be solved by fermentation of rapeseed products, which can also be enriched with selected microelements through biosorption. Therefore, the aim of this study was to determine the biosorption capacity of fermented rapeseed meal (FRSM) by enriching its biomass with Cu(II), Mn(II), Zn(II), and Fe(II) ions and then using the FRSM prepared in this way in laying hens’ diet and examining its impact on performance, egg quality and transfer of microelements to eggs content. Seventy-two laying hens of the Lohmann Brown line (26 weeks of age) were used in the experiment. The experiment lasted 90 days. The birds were randomly divided into two experimental groups, each group consisted of 12 replications (cages), and each replication of 3 hens (36 birds per group). The first group (BURSM) was the control group and received 30 g/kg unfermented rapeseed meal (URSM) after the biosorption process (enrichment in Cu(II), Mn(II), Zn(II), and Fe(II) ions) in the feed, the second group (BFRSM) received 30 g/kg of fermented rapeseed meal (FRSM) after the biosorption process (enrichment in Cu(II), Mn(II), Zn(II), and Fe(II) ions) in the feed. The results conclude that both URSM and FRSM can be used as a substrate in the biosorption process. However, in the case of laying hens’ performance and egg quality, the form of the rapeseed meal (RSM) was not statistically significant. Hens in the BURSM group were characterized by higher bioaccumulation factor (BF), while hens from the BFRSM group were characterized by higher transfer coefficients (TC), which may be important in the design of functional foods.

Persulfate assisted photocatalytic degradation activity and mechanism of tetracycline by Cu enriched reed hydrothermal carbonization carbon: Synergistic effect and DFT calculation

Heavy metal-enriched reeds can cause secondary pollution if not handled properly, and in addition, they can enter the organisms through the food chain, which can seriously harm the ecosystem. In this study, reed straw was first converted into hydrothermal carbonization carbon (HTCC) with adsorption and photocatalytic properties by acid etching and hydrothermal carbonization, then the prepared HTCC was used for adsorption of heavy metal Cu wastewater to obtain Cu/HTCC, and finally the photocatalytic degradation of tetracycline (TC) was enhanced with the assistance of persulfate. The results showed that the enrichment of Cu did not change the structural properties of HTCC, while the Cu on the surface of Cu/HTCC formed bridging interactions with TC in solution, which improved the TC degradation by Cu/HTCC+light+PS. The degradation efficiencies of Cu/HTCC+light+PS for TC were and 99%, which were 2.5 and 4 times higher than those of Cu/HTCC+light (40%) and HTCC+light+PS (25%), respectively. The Cu/HTCC+light+PS system degraded TC well over a wide pH range and in the presence of common anions (＞80%). Density functional theory (DFT) calculations and photoelectrochemical tests showed that Cu/HTCC has a strong charge separation and charge transfer ability during the photocatalytic process, where electrons preferentially migrate from the polyfuranic chain to Cu. The degradation mechanism and degradation pathway of TC by the Cu/HTCC+light+PS system were proposed by burst experiment, EPR and HPLC-MS tests, and the toxicity of the degradation products was analyzed by using the ECOSAR procedure. This study provides a new perspective for the preparation of biomass derived green photocatalysts and shows its application in environmental remediation.

Distribution of Ag, Au, Bi, Cu, and Mo in surface soils. Case study: Mitrovica region, Republic of Kosovo

ABSTRACT This article presents the results of a geochemical investigation of an anthropogenic group of metals (Ag, Au, Bi, Cu, and Mo) in the surface of the Mitrovica region, Republic of Kosovo. In order to determine their content and to evaluate the contamination level, 156 topsoil samples were collected in an area of 301.5 km2. The content of elements was determined by inductively coupled plasma-mass spectrometry. The results showed that the average content of Cu (42 mg/kg), Bi (1.5 mg/kg), Ag (0.44 mg/kg), and Au (2.7 μg/kg) exceeded their average content in European and world soils by 3.4 and 1.4 times; 3.0 and 7.5 times; 1.62 and 8.8 times and 2.7 and 1.8 times, respectively. The average Mo content (0.68 mg/kg) exceeded the average content in European soils by 1.09 times, while the average content in world soil was not exceeded. Copper levels exceeded the Dutch target value of 36 mg/kg in 152 km2 and the Dutch action value of 190 mg/kg in 6.2 km2 of the study area. The enrichment factor and geo-accumulation index values for the analysed elements indicate that their higher content is of anthropogenic origin, mainly due to lead and zinc mining and metallurgical activities in the study area. The quality of soils in the Mitrovica region varies from highly contaminated with copper and bismuth, with extremely high enrichment of Cu, Bi and Ag in the soils of the central zone (Zone I) and the urban soils of the cities of Zveçan and Mitrovica. Therefore, the establishment of a monitoring and treatment programme for contaminated soils in this zone would be necessary to protect human health .

Understanding the role of Cu element in nanocrystalline hot deformed Nd-Fe-B magnets

Alloying with Cu element has long been established as a means of improving the performance of sintered NdFeB magnets, but its effect on nanocrystalline hot-deformed magnets has not been thoroughly discussed yet. In this study, we conducted a systematic comparison of the microstructure and magnetic properties of nanocrystalline Nd14Fe80B6 and Nd14Fe79B6Cu magnets. The results showed that the introduction of Cu significantly enhances the coercivity of both melt-spun and hot-deformed Nd-Fe-B magnets, owing to the improved magnetically decoupling between neighboring Nd2Fe14B matrix grains by the enrichment of Cu at Nd-rich grain boundary (GB) layer. Despite the magnetic dilution resulting from the introduction of non-magnetic Cu, a significant improvement of remanence from 11.0 kGs to 12.2 kGs is observed in the hot-deformed Nd-Fe-B magnet with 1 at.% Cu addition. The enhancement is attributed to the improved orientation of the Cu-added magnet, as evidenced by the preferential grain alignment from microstructural characterization. The addition of trace Cu changes the properties of the Nd-rich GB phase, lowering its melting point and improving the hot-workability of the Nd-Fe-B magnet during the hot-deformation process. Overall, this study clarifies the positive role of Cu in nanocrystalline Nd-Fe-B magnets and highlights its importance for grain alignment during hot-deformation processing.

Enhancing direct deoxygenation of m-cresol to toluene through inhibiting C-C hydrogenolysis via alloying Ni with Cu

Selective hydrodeoxygenation (HDO) of biomass lignin derived phenolics to aromatics is an attractive approach for utilization of biomass lignin, since minimal H2 is consumed. Herein, bimetallic Ni-Cu/SiO2 catalysts with varying Cu/Ni molar ratios were synthesized by a modified homogeneous precipitation-deposition method and tested for HDO of m-cresol at 350 °C and atmospheric pressure. Characterizations indicate the formation of Ni-Cu alloys with an enrichment of Cu on the surface, which breaks the contiguous surface Ni atoms and reduces the Ni ensemble size. Despite bare Ni/SiO2 favors both C-C hydrogenolysis to CH4 and direct deoxygenation (DDO) to toluene, Ni-Cu/SiO2 makes DDO the dominant pathway (yield of 7.6% at conversion of 9.6% and yield of 90.4% at conversion of 95.2%) while suppresses the C-C hydrogenolysis to a very minor one. Ni-Cu/SiO2 with an optimal Cu/Ni molar ratio of 0.5 produced a turnover frequency (TOF) of 3.09 min−1 for m-cresol conversion. The TOF for toluene formation on Ni-Cu/SiO2 increases by ∼3 times to 2.24 min−1 from that on bare Ni/SiO2 whereas the TOF of CH4 formation is reduced by ∼10 times to 0.16 min−1. This study demonstrates that dilution of Ni by an inert metal such as Cu can effectively enhance DDO through inhibiting C-C hydrogenolysis during HDO of phenolics at atmospheric pressure.

Beneficial effect of copper on pitting resistance of Ni-Cr-Fe alloys

This study examines the effect of copper alloying on pitting resistance in a model solid solution FCC Ni-13%Cr-10%Fe alloy through potentiodynamic and potentiostatic polarization in 0.1 M NaCl in conjunction with an analysis using first-principles competitive electro-chemisorption modeling. The pitting potential increased with increasing Cu content in the alloy. Furthermore, the extent of metastable pit growth was suppressed and the incubation time for metastable to stable pit transition increased with Cu content. The first-principles competitive adsorption calculations suggested that Cu alloying suppresses chloride ion adsorption on the alloy surface in a simulated pit environment, which inhibits active dissolution at the pit bottom, enhances proton adsorption, and thereby increases the local pH at the pit bottom. We propose that these two effects of Cu in solid solution combine to reduce pit stability and may act in addition to the enrichment of Cu on the corroding pit surface.

Review on metal contamination in equatorial estuaries in the Brazilian Northeast

The present study provides an overview and assessment of the metals and trace metals registered in water, sediment, and biota in estuaries of the Equatorial Zone of the Brazilian Northeast (EZBN). The study aims to compare the degree of contamination and highlight necessary complementary research. The EZBN is characterized by the transition between the humid and hot Amazonian climate and the hot and dry semiarid climate. The spatial distribution identified enrichment for Cu, Pb, Zn, Hg, and Fe in the sediment, and sequential extraction of metals suggested low to medium mobility of metals along the environments. The Parnaíba River Delta, Curimataú, and the Anil and Bacanga estuaries were the environments with the lowest sediment quality for Pb, Zn, Cu, and Fe, identified by the geoaccumulation index (Igeo). The deposits in these estuaries were related to anthropogenic contributions from domestic sewage and inadequate disposal of wastewater from shrimp farms. However, more studies to determine the natural background levels based on sediment cores and metal speciation are necessary to better differentiate between natural and anthropic sources. Oysters, carnivorous fishes, and crustaceans had the best feedback as biomonitors for Cu, Pb, Zn, and Hg, but the application of biomonitoring needs to be expanded and maintained so that the potential for environmental degradation, which can have significant consequences both for the ecosystem and for human health, can be closely monitored in the EZBN estuaries.

Distribution and sources of Ag, Au, Bi, Cu and Mo in surface soils. Case study: Mitrovica region, Republic of Kosovo

The objective of this study was to investigate the spatial distribution and content of a specificanthropogenic group of trace metals (Ag, Au, Bi, Cu and Mo) in surface soils (0 - 5 cm) of the Mitrovicaregion, Republic of Kosovo. The content of metals was determined by inductively coupled plasma - massspectrometry (ICP-MS). The average content of Cu (42 mg/kg), Bi (1.5 mg/kg), Ag (0.44 mg/kg) and Au(2.7 μg/kg) exceeded the average content of metals in European and world soils by 3.4 and 1.4 times, 3.0and 7.5 times, 1.62 and 8.8 times and 2.7 and 1.8 times, respectively. The average Mo content of 0.68 mg/kgexceeded the mean Mo content in European soil by 1.09 times, while the mean content in world soils wasnot exceeded. Copper levels were also found to exceed the Dutch target value of 36 mg/kg in 152 km2 andthe Dutch action value of 190 mg/kg on 6.2 km2 of the 301.5 km2of the study area. The values of theenrichment factor (EF) for the analyzed elements are all above 1.5, indicating that their higher content is ofanthropogenic origin, mainly due to lead and zinc mining and metallurgical activities in the study area. Thequality of the soils in the Mitrovica region varies from heavily contaminated with copper and bismuth, withextremely high enrichment of Cu, Bi and Ag in the soils of the central zone (Zone I) and the urban soils ofthe cities of Zveçan and Mitrovica.

Pollution characteristics, associated risks, and possible sources of heavy metals in road dust collected from different areas of a metropolis in Vietnam.

Road dust samples were collected from different areas in Ho Chi Minh City (HCMC)-the largest city in Vietnam to explore pollution characteristics, ecological and human health risks, and sources of heavy metals (HMs). Results revealed the level of HMs found in the samples from residential and industrial zones of HCMC in the order of Mn > Zn > Cu > Cr > Pb > Ni > Co > As > Cd, Zn > Mn > Cu > Cr > Pb > Ni > Co > As > Cd. Due to the high enrichment of Cu, Zn in residential areas and Cu, Pb, Zn in industrial areas, the HM contamination in these areas remained moderate to severe. The findings also revealed a rising trend in the level of HMs in road dust from the east to the west of HCMC, and a heavy metal contamination hotspot in the west. In addition, industrial areas were more contaminated with HMs, posing greater associated risks than residential areas. Children living in urban areas of HCMC were found to be exposed to unacceptable health risks. Meanwhile, adults living in industrial areas face intolerable cancer risk. Among the nine HMs, Cd, Pb, and Cu posed the greatest ecological risk, while Cr and As were the main culprits behind health risks. HMs in road dust might derive from non-exhaust vehicular emissions, crustal materials, and industrial activities. The results suggested that industrial areas to the west of HCMC should focus more on reducing and controlling severe pollution of HMs.