Zn Cr Research Articles

Effect of Zn Addition on Phase Evolution in AlCrFeCoNiZn High‐Entropy Alloy

The addition of Zn to AlCrFeCoNi high‐entropy alloy (HEA) poses intriguing questions as to how it would affect phase evolution. Herein, the phase evolution in AlCrFeCoNiZn is studied using a combination of experimental techniques (X‐ray diffraction, scanning electron microscopy, energy‐dispersive spectroscopy, and differential scanning calorimetry) and computational (density‐functional theory [DFT], calculation of phase diagrams, and machine‐learning) methods. Mechanically alloyed and spark‐plasma‐sintered AlCrFeCoNiZn assumes a metastable single‐phase, body‐centered‐cubic (BCC) structure that undergoes diffusion‐controlled phase separation upon subsequent heat treatment to form separate (Al, Cr)‐rich, (Fe, Co)‐rich, and (Zn, Ni)‐rich phases. The formation of (Al, Cr)‐rich phase, not reported previously in AlCrFeCoNi‐based HEAs, is attributed to strong clustering tendency of Cr–Zn and Cr–Ni pairs, combined with the strong ordering of Zn–Ni pair, driving out Cr that in turn combines with Al to form a (Al, Cr)‐rich phase. In the DFT results, the formation of thermodynamically stable L12 phase is shown wherein Cr–Fe–Zn [Al–Ni‐Co] preferably occupy1a (000) [3c (0 ½ ½)] positions. The sluggish diffusional transformation to L12 phase from BCC precursors is attributed to the small stacking‐fault energy of AlCrFeCoNiZn. The equilibrated HEA exhibits a high microhardness of 8.24 GPa with an elastic modulus of 184 GPa.

Comparative study of chemical speciation and leaching feature of typical heavy metals in coarse and fine slags from the entrained-flow coal gasification

ABSTRACT The dissimilarity in chemical speciation and release properties of heavy metals will result in varying levels of environmental hazards and potential applications of coal gasification coarse and fine slags. The distribution, chemical speciation, leaching features, and potential environmental risks of heavy metals (Cr, Cu, Cd, Zn, Pb, and Mn) in coarse and fine slags from different coal gasification processes were revealed and compared by the sequential chemical extraction method, Horizontal vibration method, and pH-dependent leaching experiments. The results show that Cr (516.78 mg/kg) in coarse slag, Zn (348.50 mg/kg) and Pb (214.78 mg/kg) in fine slag are highly enriched and the content exceeds the screening value, indicating the need for better management during stockpiling and landfilling. The distribution of Cr, Cu, Pb, and Mn in residual state, Zn in Fe-Mn oxide bound state, and Cd in unstable bound state is the highest in both coarse slag and fine slag. The leaching toxicity of heavy metals (HMs) does not exceed the standard, but the leachate is classified as Level V surface water or groundwater quality due to the leaching concentration of Pb exceeding 0.1 mg/L. Furthermore, leaching of Cr, Zn, Cd, and Pb in fine slag is much more dependent on pH compared to coarse slag, and the concentrations of Zn and Pb exceed emission standards at pH < 3.0. The high concentration of heavy metals caught on the surface of fine slag is more harmful to the environment. The properties of HMs in the slags and pH of the application environment must be comprehensively considered before coal gasification slag disposal, especially fine slag.

Atomically synergistic Zn-Cr catalyst for iso-stoichiometric co-conversion of ethane and CO2 to ethylene and CO

Developing atomically synergistic bifunctional catalysts relies on the creation of colocalized active atoms to facilitate distinct elementary steps in catalytic cycles. Herein, we show that the atomically-synergistic binuclear-site catalyst (ABC) consisting of Znδ+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{{{{\\rm{Zn}}}}}}^{\\delta+}$$\\end{document}-O-Cr6+ on zeolite SSZ-13 displays unique catalytic properties for iso-stoichiometric co-conversion of ethane and CO2. Ethylene selectivity and utilization of converted CO2 can reach 100 % and 99.0% under 500 °C at ethane conversion of 9.6%, respectively. In-situ/ex-situ spectroscopic studies and DFT calculations reveal atomic synergies between acidic Zn and redox Cr sites. Znδ+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{{{{\\rm{Zn}}}}}}^{\\delta+}$$\\end{document} (0<δ<2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$0 \\, < \\, \\delta \\, < \\, 2$$\\end{document}) sites facilitate β-C-H bond cleavage in ethane and the formation of Zn-Hδ- hydride, thereby the enhanced basicity promotes CO2 adsorption/activation and prevents ethane C-C bond scission. The redox Cr site accelerates CO2 dissociation by replenishing lattice oxygen and facilitates H2O formation/desorption. This study presents the advantages of the ABC concept, paving the way for the rational design of novel advanced catalysts.

Zn–Cr pulse coatings for corrosion protection

ABSTRACT The influence of the Zn–Cr electrodeposition bath composition, cathode current density under direct current conditions, and the average pulse current density and the current density under pulse plating current conditions on the content of chromium in the obtained Zn–Cr coatings, the current efficiency and their corrosion properties were investigated. The obtained Zn–Cr coatings contained from about 0.01 wt-% to about 10 wt-%. The corrosion resistance largely depended on the chromium content of the coating, but also on the morphology and surface development. The best corrosion resistance was achieved for Zn–Cr alloy coatings obtained under impulse current conditions for average current densities 3 and 4 A dm−2, while cathodic peak current densities were 30 and 40 A dm−2.

An investigation of heavy metals concentration in rainwater and their effects on human health in Kurdistan Region, Iraq

One possible source of fresh water is rainfall. Nonetheless, the natural composition of rainwater may change due to air pollution in any areas. The Kwashe and Gara in the Duhok Governorate, in the Kurdistan region of Iraq, was selected as the study areas. Heavy metals concentration of rainwater was investigated. Seven samples were taken during rainy January and February 2023 for this investigation, and a statistical analysis was carried out to identify the factors influencing the quality of the rainwater. The concentrations of heavy metals (Zn, Pb, Ni, Cr, Cd, Mn, Cu, Fe, and Co) were measured with an atomic absorption spectrophotometer (AAS) and compared to WHO standards. The purpose of the study was to compare the heavy metal content of study area rainwater to WHO standards in order to determine the effects of these metals on community members' individual health as well as the environment. The heavy metal concentrations dropped in the following order: (Zn, Pb, Ni, Cr, Cd, Mn, Cu, Fe, and Co in Kwashe and Zn &gt; Ni &gt; Cu &gt; Pb &gt; Cr &gt; Fe &gt; Mn &gt; Cd &gt; Co in Gara). The following heavy metals are within the WHO's permissible limit: Fe, Cu, Zn, Mn, and Co; the others exceeded it. The results indicate that the rainwater sources in the study areas are unsafe and unfit for human consumption. Because of this, rainwater from research areas needs to be treated before drinking in order to prevent Pb, Cd, Ni, and Cr-related health problems.

Assessment of industrial effluents for heavy metals concentration and evaluation of grass (Phalaris minor) as a pollution indicator

This study was conducted to investigate the impact of industrial activities on heavy metals status in wastewater, sludge and flora on the bank of selected main drains of the Hayatabad Industrial estate, Peshawar. Plants, sludge and wastewater samples of selected sites were collected and analyzed for heavy metals distribution; cadmium (Cd), chromium (Cr), lead (Pb) and zinc (Zn) levels. Bioconcentration factor (BCF) values were calculated for plants (Phalaris minor) grass species found naturally at all sites. The results showed that the levels of metals in wastewater were lower than permissible limits except Cd and the concentration of metals in plants and sludge were within permissible limits when compared to their respective standards. Metal distribution was in the following order; sludge > plants > wastewater and the concentration of metals varied according to the distance from the source with no specific pattern. Sludge samples for all sites showed a high concentration of metals as compared to plants and wastewater samples. In grass samples, Zn was highest and Cd was low for all sites. Metals accumulation in plants was in order of; roots > shoot. Pearson's coefficient correlation showed that Cr in plant roots and Zn in shoots showed significantly high correlation with Cd in sludge while Pb in roots showed significant negative correlation with Zn in sludge. BCF values for Cr, Pb and Zn were >1, showing the phytoremediation potential of plants.

Structural, morphological, XPS, dielectric and spectral properties of sol-gel synthesized Ba–Zn–Cr U-type nanocrystalline magnetic oxide materials

Polycrystalline Cr3+ substituted Ba4Zn2Fe36-xCrxO60 (Zn2U) U-type hexaferrite compositions Ba4Zn2Fe36-xCrxO60 (x = 0.0, 0.5, 1.0, 1.5, and 2.0) were fabricated using the sol-gel self-ignition technique. U-type hexaferrite structure was achieved by sintering the powdered samples for 6 h at 1200 °C in a muffle furnace. The phase identification and structural parameters of Zn2U hexaferrites were evaluated by X-ray diffraction peaks of the powdered samples. Lattice parameters (a,c) and unit cell volume decreased upon Cr3+ substitution. The crystallite size was measured between 61 and 57 nm. FTIR spectra revealed the existence of specific absorption (Fe–O) bands at wavenumbers 419 and 539 cm−1. These bands further verify the formation of U-type hexaferrite. SEM micrographs showed the platelet-like morphology of the grains with proper hexagonal structure. X-ray photoelectron spectroscopy (XPS) results confirmed the existence of all metal ions with their corresponding electronic states. The dielectric response of the fabricated Zn2U U-type hexaferrite pellets was investigated at room temperature through a vector network analyzer with a wide frequency band from 1 MHz to 6 GHz. Dielectric constant (εʹ) was increased for the compositions x = 1.0 and 1.5 while dielectric loss (εʺ), tangent loss (tanδ), and ac conductivity (Ϭac) were reduced upon Cr3+ substitution. Single semicircles in the impedance Cole-Cole plots revealed that grain boundaries play a vital role in the conduction process of prepared U-type hexaferrites. Microwave absorption (MW) was improved with Cr3+ substitution. The minimum reflection loss (RL) of −53dB (99.99% MW absorption) at frequency 1.3 GHz was obtained for composition x = 0.5. The dielectric analysis (low losses and high Q-values) of the prepared hexaferrites predicts their appropriate use in high-frequency device applications.

Study of Heavy Metal Content in Lola Snail (Trochus niloticus) in The Karang Island of Central Tapanuli Regency

Research on the analysis of heavy metal content in the waters of Karang Island, Central Tapanuli Regency aims to know the metal content in Lola Snail meat, sediment, and Lola Snail shells. The research method begins with taking samples of Lola snails and sediments on Karang Island and preparing the samples. Then, the samples were analyzed by AAS (Atomic Absorption Spectrometry) to determine the content of heavy metal elements in the meat of Lola Snail, followed by XRD (X-Ray Diffraction) testing to determine the content of heavy metal elements in sediments, and also testing with EDX (Energy Dispersive X-Ray) to determine the content of heavy metals in the shell. The results of the analysis on the AAS test showed that the order of heavy metal concentrations in Lola snail meat at station I was Zn Cr Cu Cd Pb, while at station II was Zn Cu Cr Cd Pb. The results of the sequence of heavy metal concentrations using XRD in sediments around Karang Island at the station I was Zn Cr Cu Cd Pb, while at station II was Zn Cd Cu Cr Pb. The results of the analysis on the shells of Lola snails using EDX at both stations showed they did not contain heavy metal elements (Pb, Cd, Cu, Cr, and Zn), but only contained O, Ca, Mg, Na, Al, and Si elements.

Fabrication and elucidation of electromagnetic characteristics in Cr–Zn co-substituted strontium hexaferrite for high-frequency device applications

Fabrication and elucidation of electromagnetic characteristics in Cr–Zn co-substituted strontium hexaferrite for high-frequency device applications

Metal pollution in freshwater fish: A key indicator of contamination and carcinogenic risk to public health

Metals are micropollutants that cannot be degraded by microorganisms and are infiltrated into various environmental media, including both freshwater and marine water. Metals from polluted water are absorbed by many aquatic species, especially fish. Fish is a staple food in the diets of many regions in the world; hence, both the type and concentration of metals accumulated and transferred from contaminated water sources to fish must be determined and assessed. In this study, the heavy metal concentration was determined and assessed in fish collected from freshwater sources via published literature and Estimated Daily Intake (EDI), Target hazard quotient (THQ), and Carcinogenic Risk (CR) analyses, aiming to examine the metal pollution in freshwater fish. The fish was used as a bioindicator, and Geographic information system (GIS) was sued to map the polluted regions. The results confirmed that Pb was detected in fish sampled at 28 locations, Cr at 24 locations, Cu and Zn at 30 locations, with values Pb detected ranging from 0.0016 mg kg−1 to 44.3 mg kg−1, Cr detected ranging from 0.07 mg kg−1 to 27 mg kg−1, Cu detected ranging from 0.031 mg kg−1 to 35.54 mg kg-1, and Zn detected ranging from 0.242 mg kg−1 to 103.2 mg kg−1. The strongest positive associations were discovered between Cu–Zn (r = 0.74, p < 0.05) and Cr–Zn (r = 0.57, p < 0.05). Spatial distribution maps depicting the consumption of fish as food and its corresponding Pb and Cr intake revealed a higher incidence of both carcinogenic and non-carcinogenic health concerns attributed to Pb and Cr in the region with populations consuming the fish.

Joint Effect of Multiple Metals on Hyperuricemia and Their Interaction with Obesity: A Community-Based Cross-Sectional Study in China.

Metal exposures have been inconsistently related to the risk of hyperuricemia, and limited research has investigated the interaction between obesity and metals in hyperuricemia. To explore their associations and interaction effects, 3300 participants were enrolled from 11 districts within 1 province in China, and the blood concentrations of 13 metals were measured to assess internal exposure. Multivariable logistic regression, restricted cubic spline (RCS), Bayesian kernel machine regression (BKMR), and interaction analysis were applied in the single- and multi-metal models. In single-metal models, five metals (V, Cr, Mn, Co, and Zn) were positively associated with hyperuricemia in males, but V was negatively associated with hyperuricemia in females. Following the multi-metal logistic regression, the multivariate-adjusted odds ratios (95% confidence intervals) of hyperuricemia were 1.7 (1.18, 2.45) for Cr and 1.76 (1.26, 2.46) for Co in males, and 0.68 (0.47, 0.99) for V in females. For V and Co, RCS models revealed wavy and inverted V-shaped negative associations with female hyperuricemia risk. The BKMR models showed a significant joint effect of multiple metals on hyperuricemia when the concentrations of five metals were at or above their 55th percentile compared to their median values, and V, Cr, Mn, and Co were major contributors to the combined effect. A potential interaction between Cr and obesity and Zn and obesity in increasing the risk of hyperuricemia was observed. Our results suggest that higher levels of Cr and Co may increase male hyperuricemia risk, while higher levels of V may decrease female hyperuricemia risk. Therefore, the management of metal exposure in the environment and diet should be improved to prevent hyperuricemia.

Comparison of the corrosion resistances of chromium-passivated and cerium-passivated Zn/NdFeB magnets

Abstract Chromium-free passivation of Zn coating on NdFeB magnets becomes a research hotspot due to the serious harm of chromium ions to the human body. Chromium-based and cerium-based passivation technologies are conducted on electroplating Zn/NdFeB respectively. Morphologies, elemental compositions and phase structures of the two passivated coatings are characterized by scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The corrosion resistances of the two passivated specimens are compared by neutral salt spray test, accelerated aging test and electrochemical measurements. A complete and smooth passivation film can be obtained on the surface of Zn/NdFeB, filling the gaps and pores in Zn coating. Compared with un-passivated Zn/NdFeB, Zn(Ce)/NdFeB and Zn(Cr)/NdFeB possess excellent corrosion resistance. In comparison, Zn(Ce)/NdFeB possesses excellent anti-corrosion performance, increasing the red-rust appearing time from 288 to 432 h, which is still lower than that of Zn(Cr)/NdFeB (528 h). Therefore, the self-repair effect of cerium passivation technology during the corrosion process should be further studied to achieve the purpose of replacing chromium passivation technology.

BEHAVIOR OF HEAVY METALS IN SOIL-CONDENSATE-PLANTS SYSTEM IN THE ULAN-UDE LANDFILLS

The impact of waste dumps on environmental components, i.e., soil, evaporating soil water (condensate) and plants is studied. It has been revealed that industrial and municipal waste dumps continue to affect significantly the environment after their closure. The behavior of heavy metals (Pb, Cu, Zn, Ni, Cd, Co, Sb, Sn, Bi, Hg, and Cr) in soils, plants, and condensate in landfill areas and beyond them (the background) has been studied in detail. It has been found out that soils, plants and condensate at landfills are enriched in heavy metals as compared to the background sites. The degree of soil contamination at waste dumps depends on the reclamation stage of the latter. The landfill soils exceed the norms of maximum permissible concentrations for heavy metals by 1.1–90 times. Concentrations of heavy metals in plants exceed the background values from 1.1 to 104 times at all dumps. The maximum level of heavy metals in plants is exceeded for Zn, Cd, Cr. In the condensate sampled at the dumps, MPC is exceeded for Cu, Zn, and Hg. Based on the analysis results, the geochemical rows of heavy metal distribution in different landfill environments were compiled: in plants – Zn Cu Cr Ni Pb Cd Co Hg Sn Bi; in condensate – Zn Cu Ni Cr Pb Sn Co Hg Sb Cd Bi; in the soil – Zn Cr Cu Ni Pb Co Sb = Sn Cd. The distribution of heavy metals in the condensate and plants is similar. In these environments, contribution of Zn and Cu is more than 80%, contribution of Cr, Ni, Pb varies from 1 to 10%; contribution of Cd, Co, Sb, Sn, Bi, Hg is less than 1%. Heavy metals are distributed in soil according to a different pattern: the main contributors are Zn and Cr (their input is more than 50%), then go Ni, Cu, Co, and Pb (their content in soil varies from 1 to 50%), followed by Sb, Sn, and Cd (their content is less than 1%). Total pollution indices (Zc) of the soil, condensate and plants have been calculated for each landfill. Based on Zc, the landfills were grouped in a ranking series, which can form the basis for assigning the sequence of landfill reclamation measures.

Elemental Abundances of Moon Samples Based on Statistical Distributions of Analytical Data

The successful return of Chang’E-5 (CE5) samples urges the hot topic of the study of the Moon in geochemistry. The elemental data of the analyzed moon samples reported in the literature were collected to determine the elemental abundances in moon samples. Based on 2365 analytical records of moon samples from ten missions of Apollo, Luna, and CE5, elemental abundances of 11 major oxides including Cr2O3, 50 trace elements including Ti, P, Mn, Cr, and 15 rare earth elements (REEs) including Y are derived based on statistical distributions of normal, log-normal, and additive log-ratio transformation, respectively. According to the value of 13.5% CaO content, moon samples are classified into two types, as low-Ca and high-Ca samples, whose elemental abundances are also calculated respectively based on the methods used in the total moon samples. With respect to the mid-ocean ridge basalt (MORB) of the Earth, moon samples (including the Moon, low-Ca, and high-Ca samples) are rich in Cr, REEs, Th, U, Pb, Zr, Hf, Cs, Ba, W, and Be and poor in Na, V, Cu, and Zn in terms of their concentrations, and are enriched in Cr and depleted in Na, K, Rb, P, V, Cu, Zn in spider diagrams. The CE5 sample is a low-Ca type of moon sample and is clearly rich in Ti, Fe, Mn, P, Sc, REEs, Th, U, Nb, Ta, Zr, Hf, Sr, Ba, W, and Be and poor in Mg, Al, Cr, and Ni in terms of their concentrations relative to the moon or the low-Ca samples. If compared with the moon sample, the CE5 sample is also clearly rich in K, REE, and P.

Partial correlation of optical, electrical and magnetic properties of nanosized Zn–Cr–La ferrite particles synthesized by sonochemical method

Zn0.5Cr0.5LaxFe2-xO4 nanoferrites with varied compositions of x = 0.03, 0.06, 0.09, and 0.12 were synthesized using an effective sonochemical reactor. The powders resulting from this synthesis were characterized by X-ray diffraction (XRD) and scanning electron microscopy, energy dispersive X-ray spectroscopy, and their electrical and magnetic properties examined by electrochemical impedance spectroscopy and vibrating sample magnetometer, respectively. The XRD analysis confirms the creation of cubic crystalline structure with the crystallite size from 38 (x = 0.12) to 57 (x = 0.03) nm. The lattice constant of the ferrite nanoparticles is found to decrease with La content. Using XRD patterns, the development of a cubic crystalline structure was revealed. An increase in the amount of La3+ ions in Zn0.5Cr0.5LaxFe2-xO4 nanoferrites could explain the decrease in crystalline size. In Zn0.5Cr0.5LaxFe2-xO4 nanoferrites, impedance investigation revealed the presence of pseudo-capacitance and resistive behavior. The conductivity of Zn0.5Cr0.5LaxFe2-xO4 nanoferrites was also slightly reduced when La3+ ions were added. The soft ferromagnetic behavior of Zn0.5Cr0.5LaxFe2-xO4 nanoferrites was aided by the hysteresis loops. An increase in the La content of Zn0.5Cr0.5LaxFe2-xO4 nanoferrites resulted in a decrease in saturation magnetization and an increase in coercivity.

Generation of Geochemical Exploration Targets from Regional Stream Sediment Data Using Principal Component and Factor Ana

A regional-scale stream sediment geochemical sampling was carried out with an averagesampling density of one sample per nine square-kilometre in Kiteto District, Manyara Region.A total of 358 stream sediment samples were collected and analysed for major and traceelements by X-ray fluorescence (XRF) and fire assay with atomic absorption spectrometry(AAS) finish methods. In this study, Factor and Principal Component Multivariate (FPCM)analyses have been used to the stream geochemical data to delineate potential mineralizationzones by plotting correlated factors as geochemical anomaly maps. Four factors that accountfor 73.7% of the total variance of the stream sediment geochemical data were established.Factor 1: Ni–Ba–Co–Cu–Sr which possibly defines the underlying metamorphosed graniticunits with some contribution from mafic and ultramafic rocks. Factor 2: Cr–Zn–Mn whichdefines crustal forming elements reflecting the mafic rocks. Factor 3 which entails Rb and Pbprobably attributed to metamorphosed granitic lithology. Factor 4 is arsenic, a chalcophileelement with affinity to sulfide phases. The FPCM analyses have been successfully indelineating potential target areas for gold, nickel and copper exploration in the study area.&#x0D; Keywords: Stream sediment; principal component; factor analysis; exploration targets;Kibaya-Kiteto, Manyara.

Sustainable utilization of unavoidable food waste into nutritional media for the isolation of bacterial culture for the removal of heavy metals

This study aims to reuse food waste (FW) as growth media for bacterial cultures for bioremediation of heavy metal. The best natural medium was selected based on the carbon, nitrogen, and other elements. The batch culture of Comamonas terrae showed growth stability for 16 days in the pig bone medium. C. terrae showed the best growth at pH of 7.4, temperature of 35 °C, and medium concentration of 10 g/L. The C. terrae showed heavy metal (HM) removal efficiencies of Cd (52 %) Cr (63 %) Pb (62 %) and Zn (55 %). In addition, the Fourier transform infrared spectroscopy results revealed the bioadsorption of HM in C. terrae. The study suggests the C. terrae can efficiently remove HM and C. terrae may be used for bioremediation of HM. Therefore, pig bone waste is a cost-effective medium and a good solution for the valorization and reuse of FW in line with the circular economy.

Simultaneous in Situ Exfoliation of Titanate and Zn–Cr Layered Double Hydroxides with a Copolymer for Photocatalytic Degradation of Organic Pollutants

Simultaneous <i>in Situ</i> Exfoliation of Titanate and Zn–Cr Layered Double Hydroxides with a Copolymer for Photocatalytic Degradation of Organic Pollutants

Mineralogy and Geochemistry of beach sediments associated with the Precambrian crystalline rocks (Vijayan Complex) of Sri Lanka; perspective for heavy minerals

Southeastern landmass of Sri Lanka is laid on the Vijayan Complex (VC) rocks, a Precambrian basement characterized with specific geological features since the mineralized contact zone of the Highland–Vijayan boundary is nearby. However, the coastal sedimentation of such a basement is rarely interpreted. Hence, the mineralogy and geochemistry of surface sediments exposed along 45 km long southeast (SE) coast were studied to find the compositions and to interpret the terrestrial compart. Studied beach faces expose as sandy siliciclastic sediments with scatter depositions of black and red coloured heavy sediments, as 10–15 cm beds, within 1–3 km from deltaic environments. X-ray diffraction analysis of such heavy placers indicate the presence of predominant ilmenite, almandine garnet, zircon, monazite and ferrihydride. The sediments from other areas are rich in lighter minerals of quartz, albite and magnesium-calcite representing the average beach sediment mineralogy of SE coast. Upper continental crust normalized X-ray fluorescence data show an enriched tendency of Zr (9.8) > V > Nb > Th > TiO2 (6.2) > Cr (2.5) > MnO > Fe2O3 > As > Y > Zn and depleted tendency of Pb (0.8) > CaO >P2O5 > Sr > Sc > Cu (0.1) indicating the leachability of depleted elements and strong recycling processes of High Field Strength Elements (HFSE). Hierarchical cluster analysis and Pearson correlation matrixes indicate the presence of four geochemically related sample clusters. These analyses further showed that the cluster 1 relates to heavy sediments deposits with higher terrigenous influences while cluster 4 relates to siliciclastic sediments with higher marine influences. Hence, geochemical anomalies of cluster 1 to 4 show decreasing abundances for HFSE and opposite tendencies for CaO, Sr, I, Br, and F confirming the mineralogical results. Higher terrigenous influenced sediment samples evident for the presence of solid phases of titanium carriers (As–V–TiO2), phosphorus–HFSE carriers (Pb–Th–P2O5–Y–Cl–Nb–Zr), authigenic carbonates (Sr–Br–CaO) and Fe–Mn coatings (Zn–Cr–MnO–Fe2O3–Cu). Compatibility variable ratios of Th/Sc, Zr/Sc, TiO2/Zr, Cr/Th and V/Th respectively show 15.16, 364.38, 20.85, 2.95 and 9.73 values for these coastal sediments. Based on the published international and VC average lithological data, the present study concluded that the primary sources for the sedimentation have felsic signatures showing relations to granitic gneisses and granitic intrusive rocks of the VC. Apart from the terrestrial provenances, the coastal area has been affected by lower secondary influences of anthropogenic, marine inorganic and organic matters.

Potential Sources, Pollution, and Ecological Risk Assessment of Potentially Toxic Elements in Surface Soils on the North-Eastern Margin of the Tibetan Plateau.

Due to increased levels of human activity, various pollutants are frequently detected on the Tibetan Plateau, where the environment is extremely fragile and sensitive. Therefore, this study investigated the sources, pollution, and ecological risks of soil potentially toxic elements (PTEs) in different landscape areas within the Qaidam Basin in the northeastern part of the Qinghai–Tibet Plateau. The contents of seven PTEs (Cd, Cu, Pb, Zn, As, Cr, and Ni) in 32 topsoil samples (0–2 cm) were analyzed in different regions of the Qaidam Basin. The concentrations of As, Cd, Cr, Cu, Ni, Pb, and Zn were 10.4–29.9 mg/kg, 0.08–4.45 mg/kg, 19–66 mg/kg, 8.2–40 mg/kg, 11.7–30.8 mg/kg, 11.1–31.2 mg/kg, and 32–213 mg/kg, respectively. The correlation between Pb and Cd in unpopulated areas was 0.896 (p < 0.01). The correlations among Pb, Cd, and Zn in agricultural areas, among As, Cd, Cr, and Zn in saline lake areas, and among As, Cd, Cr, Cu, Ni, Pb, and Zn in residential areas were all greater than 0.65 (p < 0.05). The principal component analysis results showed that Pb and Cd in unpopulated areas, Pb, Cd, and Zn in agricultural areas, As, Cd, Cr, Zn, and Pb in saline lake areas, and As, Cd, Cr, Cu, Ni, Pb, and Zn in residential areas were affected by human activities (significant factor >0.70). Based on the geological accumulation index and single-factor pollution index results, the maximum Cd values were found to be 4.93 and 45.88, respectively; Cd was thus the most serious PTE pollutant. The comprehensive pollution index of Nemero showed that moderately and severely polluted areas accounted for 18.89% and 18.46% of the total area, respectively. The results of the potential risk index showed that very strong and strong ecological risk points together accounted for 18.8% of the total points. The spatial variations in PTE pollution and the potential ecological risk index had similar patterns; both increased from the unpopulated areas in the northeastern Qaidam Basin to Golmud city in the south-western Qaidam Basin. These results indicate that human activities negatively impacted the soil ecological environment in the Qaidam Basin during the rapid development of the economy and urbanization and that these negative impacts tended to spread to unpopulated areas. Therefore, it is necessary to emphasize the significant impacts of human activities on environmental quality and formulate preventive measures to reduce PTE pollution in the Qinghai–Tibet Plateau.