High Concentrations Of Cobalt Research Articles

Structure analysis of bacterial community and their heavy-metal resistance determinants in the heavy-metal-contaminated soil sample

AbstractIn this study we performed the phylogenetic analysis of non-cultivable bacteria from anthropogenically disturbed soil using partial sequences of the 16S rRNA (16S rDNA) and the heavy-metal resistance genes. This soil sample contained high concentrations of nickel (2,109 mg/kg), cobalt (355 mg/kg) and zinc (177 mg/kg), smaller concentrations of iron (35.75 mg/kg) and copper (32.2 mg/kg), and also a trace amount of cadmium (<0.25 mg/kg). The 16S rDNA sequences from a total of 74 bacterial clones were distributed into four broad taxonomic groups, Acidobacteria, Actinobacteria, Bacteroidetes and Gemmatimonadetes, and some of them were unidentified. Comparing our clone sequences with those from the GenBank database, only 9 clones displayed high similarity to known bacteria belongig to actinomycetes; others were identified as uncultured ones. Among clones evidently Actinobacteria predominated. Sixteen clones from soil sample carried only the nccA-like heavy-metal-resistance genes and all sequences showed too low similarity to known proteins encoded by these genes. However, our results suggested that the heavy-metal-contaminated soil is able to present very important reservoir of the new and until now unknown partly bacteria, partly heavy-metal-resistance determinants and their products. Bacteria and nccA-like genes identified in this study could represent the objects of interest as bioremediation agents because they can be potentially used in different transformation and immobilization processes.

Transition in spin dependent transport from superparamagnetic-superparamagnetic to superparamagnetic-ferromagnetic in sputtered Cu100–xCox granular films

The transition in the spin-dependent transport from superparamagnetic-superparamagnetic (SPM-SPM) to superparamagnetic-ferromagnetic (SPM-FM) in room temperature co-sputtered granular Cu100−xCox (x = 15.1–30.9 at. %) thin films is tracked by varying the cobalt concentration. It is found that at lower cobalt concentrations of x ≤ 20.9, the spin dependent transport is governed by the scattering which electrons undergo while they move through SPM-SPM network. At higher cobalt concentration x > 20.9, the transport behavior changes due to predominant electronic scattering through SPM-FM networks. From the isothermal magnetoresistance behavior in 20–300 K range, transmission electron microscopy analysis, and magnetization behavior, three different composition regimes are identified. These are (i) x ≤ 15.1, consisting of nearly spherical monodispersed single uncoalesced non-interacting small SPM particles only; (ii) 15.1 < x ≤ 20.9, having bimodal distribution with small monodispersed SPM and weakly interacting bigger SPM particles, and (iii) x > 20.9, having monodispersed small SPM particles and FM clusters having broad distribution with stronger interactions. The work provides an insight to understand the transition of spin dependent transport from SPM-SPM to SPM-FM and the gradual increase in the strength of magnetic interaction among the particles vis-à-vis cobalt concentration.

Concentrations and forms of heavy metals around two ore processing sites in Katanga, Democratic Republic of Congo

The concentration of heavy metals and the forms in which they occur were determined for tailings and derived deposits of two major processing sites of Cu–Co and Cu–Zn–(Pb) ores in the Katanga Copperbelt (Kipushi, Likasi). They were studied by a combination of methods, focussed on the nature of water- and EDTA-extractable compounds, the mineralogical composition of tailings and associated secondary minerals, and textural features of metal-bearing efflorescences. For the Kipushi area, sulfide minerals in tailings of decantation basins are identified as the source of extractable metals they contain, but input from an external source rather than local oxidation of substrate components is responsible for high levels of contamination in the Likasi area. Contaminated areas around Likasi are characterized by an abundance of Mg-sulfate efflorescences with high concentrations of cobalt and other metals, acting as an important vector for further dispersion of contaminants by wind and water.

In vivo corrosion, tumor outcome, and microarray gene expression for two types of muscle-implanted tungsten alloys

Tungsten alloys are composed of tungsten microparticles embedded in a solid matrix of transition metals such as nickel, cobalt, or iron. To understand the toxicology of these alloys, male F344 rats were intramuscularly implanted with pellets of tungsten/nickel/cobalt, tungsten/nickel/iron, or pure tungsten, with tantalum pellets as a negative control. Between 6 and 12months, aggressive rhabdomyosarcomas formed around tungsten/nickel/cobalt pellets, while those of tungsten/nickel/iron or pure tungsten did not cause cancers. Electron microscopy showed a progressive corrosion of the matrix phase of tungsten/nickel/cobalt pellets over 6months, accompanied by high urinary concentrations of nickel and cobalt. In contrast, non-carcinogenic tungsten/nickel/iron pellets were minimally corroded and urinary metals were low; these pellets having developed a surface oxide layer in vivo that may have restricted the mobilization of carcinogenic nickel. Microarray analysis of tumors revealed large changes in gene expression compared with normal muscle, with biological processes involving the cell cycle significantly up‐regulated and those involved with muscle development and differentiation significantly down‐regulated. Top KEGG pathways disrupted were adherens junction, p53 signaling, and the cell cycle. Chromosomal enrichment analysis of genes showed a highly significant impact at cytoband 7q22 (chromosome 7) which included mouse double minute (MDM2) and cyclin‐dependant kinase (CDK4) as well as other genes associated with human sarcomas. In conclusion, the tumorigenic potential of implanted tungsten alloys is related to mobilization of carcinogenic metals nickel and cobalt from corroding pellets, while gene expression changes in the consequent tumors are similar to radiation induced animal sarcomas as well as sporadic human sarcomas.

Scientific Opinion on safety and efficacy of coated granulated cobaltous carbonate monohydrate as feed additive for all species

Cobalt(III) is a component of cobalamin. Its essentiality as trace element results from the capacity of certain animal species to synthesise cobalamin by the gastrointestinal microbiota. Feeding cobalt(II) carbonate hydroxide (2:3) monohydrate up to the maximum authorised total cobalt in feed is safe for the target animals. Cobalt is predominantly excreted via the faecal route. Absorbed cobalt follows aqueous excretion routes. About 43 % of body cobalt is stored in muscle; however, kidney and liver are the edible tissues containing the highest cobalt concentrations and are most susceptible to reflect dietary cobalt concentrations. In animals with the capacity to synthesise cobalamin, cobalt is also deposited in tissues as vitamin B12. Cobalt(II) cations are genotoxic under in vitro and in vivo conditions. Cobalt(II) carbonate has carcinogen, mutagen and reproduction toxicant (CMR) properties. No data are available on the potential carcinogenicity of cobalt(II) following oral exposure. However, oral exposure may potentially entail adverse threshold-related effects in humans. The estimated population intake of cobalt most likely includes the contribution of foodstuffs from animals fed cobalt-supplemented feedingstuffs. An increase in cobalt exposure by the use of cobalt-containing feed additives is therefore not expected. Considering the population exposure to cobalt, about 4–10 times lower than the health-based guidance value, no safety concern for the consumer is expected for threshold effects of oral cobalt. Cobalt(II) carbonate is a skin and eye irritant, and a dermal and respiratory sensitiser. Its dust is a hazard to persons handling the substance. Exposure by inhalation must be avoided. The use of cobalt from any source at the authorised maximum content in feed does not provide a risk to the environment. The coated granulated cobalt(II) carbonate hydroxide (2:3) monohydrate is available for cobalamin synthesis in the rumen and therefore effective in ruminants; this conclusion is extrapolated to horses and rabbits.

Basin‐scale inputs of cobalt, iron, and manganese from the Benguela‐Angola front to the South Atlantic Ocean

We present full‐depth zonal sections of total dissolved cobalt, iron, manganese, and labile cobalt from the South Atlantic Ocean. A basin‐scale plume from the African coast appeared to be a major source of dissolved metals to this region, with high cobalt concentrations in the oxygen minimum zone of the Angola Dome and extending 2500 km into the subtropical gyre. Metal concentrations were elevated along the coastal shelf, likely due to reductive dissolution and resuspension of particulate matter. Linear relationships between cobalt, N2O, and O2, as well as low surface aluminum supported a coastal rather than atmospheric cobalt source. Lateral advection coupled with upwelling, biological uptake, and remineralization delivered these metals to the basin, as evident in two zonal transects with distinct physical processes that exhibited different metal distributions. Scavenging rates within the coastal plume differed for the three metals; iron was removed fastest, manganese removal was 2.5 times slower, and cobalt scavenging could not be discerned from water mass mixing. Because scavenging, biological utilization, and export constantly deplete the oceanic inventories of these three hybrid‐type metals, point sources of the scale observed here likely serve as vital drivers of their oceanic cycles. Manganese concentrations were elevated in surface waters across the basin, likely due to coupled redox processes acting to concentrate the dissolved species there. These observations of basin‐scale hybrid metal plumes combined with the recent projections of expanding oxygen minimum zones suggest a potential mechanism for effects on ocean primary production and nitrogen fixation via increases in trace metal source inputs.

Environmental impact and vulnerability of the surface and ground water system from municipal solid waste disposal site: Koshe, Addis Ababa

Geo-environmental assessment and geophysical investigations were carried out over the only functional municipal solid waste disposal site of the city of Addis Ababa, Ethiopia, known locally as Koshe. The accumulated wastes from Koshe have impact on the surrounding human and physical environment since the disposal site was not designed. The study deserves emphasis because the city of Addis Ababa currently obtains a considerable portion of its domestic water supply from a well field developed not much farther from and along a groundwater flow direction in relation to the waste disposal site. It was found out that the leachates from the site contain high concentration of biological oxygen demand, chemical oxygen demand, chloride and sulphate besides high concentration of cobalt, nickel and zinc in the surrounding soils. The geophysical results have mapped weak zones and near-vertical discontinuities that could potentially be conduits for the leachate from the wastes into the deep groundwater system. Further, a zone of potential leachate migration from the landfill was identified from the electrical models; the location of this zone is consistent with the predicted direction of groundwater flow across the site. The results further suggested that the open dump site tends to cause increasing amount of pollution on the surrounding soil, surface and ground waters. Furthermore, it was observed that the Koshe waste disposal site has grown beyond its capacity and the poor management of the open dump landfill has reduced the aesthetic value of the surrounding environments. The need to change/relocate the existing waste disposal site to a more suitable and technologically appropriate site is emphasized.

Morphology and composition of Ni–Co electrodeposited powders

The morphology, phase and chemical composition of Ni–Co alloy powders electrodeposited from an ammonium sulfate-boric acid containing electrolyte with different ratio of Ni/Co ions were investigated. The ratios of Ni/Co ions were 1/1, 1/2 and 1/3. The morphology, chemical composition and phase composition of the electrodeposited alloy powders were investigated using AES, SEM, EDS and XRD analysis. Composition of the electrolyte, i.e. the ratio of Ni/Co concentrations was found to influence both, the alloy phase composition and the morphology of Ni–Co alloy powders. At the highest ratio of Ni/Co = 1/1 concentrations typical 2D fern-like dendritic particles were obtained. With a decrease of Ni/Co ions ratio among 2D fern-like dendrites, 3D dendrites and different agglomerates were obtained. X-ray diffraction studies showed that the alloy powders mainly consisted of the face-centered cubic α-nickel phase and hexagonal close-packed ε-cobalt phase and minor proportions of face-centered cubic α-cobalt phase. The occurrence of the latter phase was observed only in the alloy powder with the higher cobalt concentration in electrolyte. The electrodeposition of Ni–Co powders occurred in an anomalous manner.

Treatment of radioactive liquid waste (Co-60) by sorption on Zeolite Na-A prepared from Iraqi kaolin

Iraqi synthetic zeolite type Na-A has been suggested as ion exchange material to treat cobalt-60 in radioactive liquid waste which came from neutron activation for corrosion products. Batch experiments were conducted to find out the equilibrium isotherm for source sample .The equilibrium isotherm for radioactive cobalt in the source sample showed unfavorable type, while the equilibrium isotherm for the total cobalt (the radioactive and nonradioactive cobalt) in the source sample showed a favorable type. The ability of Na-A zeolite to remove cobalt from wastewater was checked for high cobalt concentration (822 mg/L) in addition to low cobalt concentration in the source sample (0.093 mg/L). A good fitting for the experimental data with Langmuir equilibrium model was observed. Langmuir constant qm which is related to monolayer adsorption capacity for low and high cobalt concentration was determined to be 0.021 and 140 mg/g zeolite. The effects of important design variables on the zeolite column performance were studied these include initial concentration, flow rate, and bed depth. The experimental results have shown that high sorption capacity can be obtained at high influent concentration, low flow rate, and high bed depth. Higher column performance was obtained at higher bed depth. Thomas model was employed to predict the breakthrough carves for the above variables. A good fitting was observed with correlation coefficients between 0.915 and 0.985.

Metallic ions released from stainless steel, nickel-free, and titanium orthodontic alloys: Toxicity and DNA damage

The aims of this study were to determine the amounts of metallic ions that stainless steel, nickel-free, and titanium alloys release to a culture medium, and to evaluate the cellular viability and DNA damage of cultivated human fibroblasts with those mediums. The metals were extracted from 10 samples (each consisting of 4 buccal tubes and 20 brackets) of the 3 orthodontic alloys that were submerged for 30 days in minimum essential medium. Next, the determination of metals was performed by using inductively coupled plasma mass spectrometry, cellular viability was assessed by using the tetrazolium reduction assay (MTT assay) (3-[4,5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide), and DNA damage was determined with the Comet assay. The metals measured in all the samples were Ti(47), Cr(52), Mn(55), Co(59), Ni(60), Mo(92), Fe(56), Cu(63), Zn(66), As(75), Se(78), Cd(111), and Pb(208). The cellular viability of the cultured fibroblasts incubated for 7 days with minimum essential medium, with the stainless steel alloy submerged, was close to 0%. Moreover, high concentrations of titanium, chromium, manganese, cobalt, nickel, molybdenum, iron, copper, and zinc were detected. The nickel-free alloy released lower amounts of ions to the medium. The greatest damage in the cellular DNA, measured as the olive moment, was also produced by the stainless steel alloy followed by the nickel-free alloy. Conversely, the titanium alloy had an increased cellular viability and did not damage the cellular DNA, as compared with the control values. The titanium brackets and tubes are the most biocompatible of the 3 alloys studied.

Levels of Pb, Fe, Cd and Co in Soils of Automobile Workshop in Osun State, Nigeria

The disposal of waste of all kinds in auto-repair workshop areas in Nigeria is becoming alarming. The study looks into the contribution of different sections in auto-repair workshop to heavy metal pollution in soil .Thirty –two soil samples were collected at an auto-repair workshop in Osogbo, Ikirun, Iragbiji and Iree in Osun State for their cobalt, iron , lead and cadmium level at different sections namely: auto-mechanicunit, auto welding unit, auto electrician unit and auto painting unit using atomic absorption spectrophotometer.The highest cobalt concentration was obtained in Iree at the auto welding unit, (17.25± 1.10mg/kg), iron had its highest level in Ikirun at the auto-mechanic unit (43937± 35mg/kg) , lead had its highest concentration in Iree at the auto welding unit (2460±16 mg/kg) and cadmium with the highest in Iree at the auto welding unit as well (2.02 ±1.01 mg/kg).Sites studied had higher levels of heavy metals compared to control areas. The general trend of dispersion of metal contamination within the soil profile is iron>> lead>> cobalt>cadmium. Statistical analysis reveals correlation between lead/iron (r = 0.636) at p

LOW TEMPERATURE SYNTHESIS AND ELECTRONIC PROPERTIES OF NTC TEMPERATURE SENSOR SPINEL-TYPE OXIDES NANOPOWDERS

NiCoxMn2-xO4(x = 0.4, 0.8, 1.2, 1.6) thermistor with nanopowders have been synthesized by the auto-combustion method at low temperatures. The size and morphology of the calcinated powders have been investigated using XRD and TEM techniques. The average particle size was estimated to be about 65 nm in diameter with the cubic and cubic + tetragonal phases for low and high cobalt concentrations, respectively. The grain size of NTC ceramics sintered at 1200°C is verified with scanning electron microscopy (SEM) images. Upon increasing the cobalt concentration, the grain size of NTC samples increases from about 2 μm to a few μm in size.The formation of spinel structure of powders has been studied by Fourier transform infrared (FTIR) spectroscopy. An ab initio calculation of electronic properties of NiCo0.8Mn1.2O4using full potential of the linear augmented plane wave (FP-LAPW) method has been performed. The results indicate that only the 3d- Mn orbitals play an important role in the conduction mechanism. The dependency of material resistivity constant (B) and temperature coefficient (α) have been measured.

Vitamin B12 biosynthesis gene diversity in the Ross Sea: the identification of a new group of putative polar B12 biosynthesizers

Vitamin B₁₂, a cobalt-containing micronutrient, has been shown to limit phytoplankton growth in the Ross Sea of the Southern Ocean. However, B₁₂ biosynthesis potential in this environment remains uncharacterized. Select bacteria and archaea synthesize B₁₂ while many phytoplankton require it for growth. Low ratios of bacterial biomass production to primary productivity and high concentrations of labile cobalt in Antarctic surface water suggest that factors controlling bacterial growth rather than cobalt availability may determine vitamin production rates here. In order to assess B₁₂ biosynthesis potential, degenerate polymerase chain reaction primers were designed to target the genetic locus cbiA/cobB, encoding cobyrinic acid a,c-diamide synthase, a B₁₂ biosynthesis protein. Sequencing the DNA compliment of Ross Sea 16S rRNA (see Supporting information) allowed targeting of cbiA/cobB probes to dominant bacterial groups. CbiA/cobB DNA sequences were successfully identified in clone libraries from the Ross Sea. To our knowledge, this study represents the first targeted molecular characterization of environmental B₁₂ biosynthesis potential. A newly identified group of cbiA/cobB sequences dominated the diversity of the sequences retrieved; their expression was confirmed via mass spectrometry-based peptide detection. These sequences seem to have originated from a previously undescribed group of bacteria that could dominate the B₁₂ biosynthesizing community in polar systems.

Effect of cobalt on Escherichia coli metabolism and metalloporphyrin formation

Toxicity in Escherichia coli resulting from high concentrations of cobalt has been explained by competition of cobalt with iron in various metabolic processes including Fe-S cluster assembly, sulfur assimilation, production of free radicals and reduction of free thiol pool. Here we present another aspect of increased cobalt concentrations in the culture medium resulting in the production of cobalt protoporphyrin IX (CoPPIX), which was incorporated into heme proteins including membrane-bound cytochromes and an expressed human cystathionine beta-synthase (CBS). The presence of CoPPIX in cytochromes inhibited their electron transport capacity and resulted in a substantially decreased respiration. Bacterial cells adapted to the increased cobalt concentration by inducing a modified mixed acid fermentative pathway under aerobiosis. We capitalized on the ability of E. coli to insert cobalt into PPIX to carry out an expression of CoPPIX-substituted heme proteins. The level of CoPPIX-substitution increased with the number of passages of cells in a cobalt-containing medium. This approach is an inexpensive method to prepare cobalt-substituted heme proteins compared to in vitro enzyme reconstitution or in vivo replacement using metalloporphyrin heme analogs and seems to be especially suitable for complex heme proteins with an additional coenzyme, such as human CBS.

The isolation of heavy-metal resistant culturable bacteria and resistance determinants from a heavy-metal-contaminated site

AbstractIn this study we performed a phylogenetic analysis of a culturable bacterial community isolated from heavymetal-contaminated soil from southwest Slovakia using 16S rRNA (16S rDNA) and heavy-metal resistance genes. The soil sample contained high concentrations of nickel (2,109 mg/kg), cobalt (355 mg/kg) and zinc (177 mg/kg), smaller concentrations of iron (35.75 mg/kg) and copper (32.2 mg/kg), and a trace amount of cadmium (<0.25 mg/kg). A total of 100 isolates were grown on rich (Nutrient agar No. 2) or minimal (soil-extract agar medium) medium. The isolates were identified by phylogenetic analysis using partial sequences of their 16S rRNA (16S rDNA) genes. Representatives of two broad taxonomic groups, Firmicutes and Proteobacteria, were found on rich medium, whereas four taxonomic groups, Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria, were represented on minimal medium. Forty-two isolates grown on rich medium were assigned to 20 bacterial species, while 58 bacteria grown on minimal medium belonged to 49 species. Twenty-three isolates carried czcA- and/or nccA-like heavy-metal-resistance determinants. The heavy-metalresistance genes of nine isolates were identified by phylogenetic analysis of their protein sequences.

Mechanism of the Catalytic Deperoxidation of tert‐Butylhydroperoxide with Cobalt(II) Acetylacetonate

The Co(II)/Co(III)-induced decomposition of hydroperoxides is an important reaction in many industrial processes and is referred to as deperoxidation. In the first step of the so-called Haber-Weiss cycle, alkoxyl radicals and Co(III)-OH species are generated upon the reaction of the Co(II) ion with ROOH. The catalytic cycle is closed upon the regeneration of the Co(II) ion through the reaction of the Co(III)-OH species with a second ROOH molecule, thus producing one equivalent of the peroxyl radicals. Herein, the deperoxidation of tert-butylhydroperoxide by dissolved cobalt(II) acetylacetonate is studied by using UV/Vis spectroscopy in situ with a noninteracting solvent, namely, cyclohexane. Kinetic information extracted from experiments, together with quantum-chemical calculations, led to new mechanistic hypotheses. Even under anaerobic conditions, the Haber-Weiss cycle initiates a radical-chain destruction of ROOH propagated by both alkoxyl and peroxyl radicals. This chain mechanism rationalizes the high deperoxidation rates, which are directly proportional to the cobalt concentration up to approximately 75 μM at 333 K. However, at higher cobalt concentrations, a remarkable decrease of the rate is observed. The hypothesis put forward herein is that this remarkable autoinhibition effect could be explained by the hitherto overlooked chain termination of two Co(III)--OH species. The direct competition between the first-order Haber-Weiss initiation and the second-order termination can indeed explain this peculiar kinetic behavior of this homogeneous deperoxidation system.

Seafloor Massive Sulfides from the Northern Equatorial Mid-Atlantic Ridge: New Discoveries and Perspectives

In addition to the two new hydrothermal fields Krasnov (l6° 38′ N) and Ashadze (13° N) discovered in 2003–2004, some later discoveries were made in the Northern Equatorial segment of the Mid-Atlantic Ridge (MAR). Two new major seafloor massive sulfide (SMS) deposits: Semyenov (13° 31′ N) and Zenith-Victory (20° 08′ N), as well as the now extended Puy des Folles hydrothermal field (20° 30.5′ N), provide enough data to make conclusions about the general characteristics of SMS deposits in the northern equatorial MAR environment. Parameters of SMS deposits, such as their distribution, geological setting, morphology, composition and age, are discussed in this paper. A majority of studied SMS deposits (Ashadze, Logatchev, Semyenov) are associated with uplifted lower crust and mantle rocks (oceanic core complex, or OCC) at the MAR segments with asymmetric mode of accretion. OCC is tectonically uplifted along with detachment faults, which exhume deep-seated rocks onto the seafloor. Detachment faults, in turn, could be the conduits for the circulation of seawater and discharge of hydrothermal fluids. Gabbro-peridotite hosted deposits are characterized by high concentrations of copper, gold and cobalt. The relationship between the size of the deposits and their age is documented.

Levels of cobalt and silver in water sources in a mining area in Ghana

The study reported herein looked at the quality of drinking water sources (underground water and river water) from a mining community in Ghana. The water samples were treated in the laboratory by acid digestionand the concentration of silver and cobalt were analysed with Atomic Absorption Spectrophotometer. The results of the analysis indicated that all the water sources of Bogoso-Domase analyzed had levels of silver andcobalt above US-EPA limit 0.01 mg/L of silver and 0.079 mg/L of cobalt. The high mean concentration of cobalt in the underground and the river water sources may have been responsible for a deep blue colour changeof the water whenever it got into contact with tannin in plant, hence affecting the cooking of certain foodstuffs such as cassava and plantain. However, these metals are seldomly discussed when it comes to those metals of concern of mining pollution. This calls for extensive research into the lesser known metals in the mining environment which might equally pose health problems since some of the studies on their cancer effect onpeople are inconclusive. Keywords; Biomagnifies, photographic industry, Telluride, Argyria, Tannin, Dumase, Bogoso.

The hydrogeochemistry of thermal springs on Mutnovskii Volcano, southern Kamchatka

This paper reports results from a hydrogeochemical study of thermal springs on Mutnovskii Volcano. The solutions of boiling pots and the pore water of thermal localities in the Donnoe Field were found to have an anomalous composition over a wide range of chemical elements, including rare earth elements (REE) and platinum-group elements (PGEs). The solutions of different springs exhibit considerable variations in their major and minor element compositions, indicating differences in the generation and upward transport of solutions. Physicochemical modeling showed that the mud pots studied could have been formed when the separate was ascending along an open fissure channel from the secondary zone of mixed boiling fluids. The high concentrations of titanium, vanadium, chromium, nickel, cobalt, REEs, and PGMs suggest a deep-seated source for these. The chemical forms of the elements in the solutions (primarily free aquaions) and the acidic environment favor high mobility of these elements. Deposition and concentration of these elements under near-surface conditions is unlikely.

Influence of Cobalt Doping on the Physical Properties of Zn0.9Cd0.1S Nanoparticles.

Zn0.9Cd0.1S nanoparticles doped with 0.005–0.24 M cobalt have been prepared by co-precipitation technique in ice bath at 280 K. For the cobalt concentration >0.18 M, XRD pattern shows unidentified phases along with Zn0.9Cd0.1S sphalerite phase. For low cobalt concentration (≤0.05 M) particle size, dXRDis ~3.5 nm, while for high cobalt concentration (>0.05 M) particle size decreases abruptly (~2 nm) as detected by XRD. However, TEM analysis shows the similar particle size (~3.5 nm) irrespective of the cobalt concentration. Local strain in the alloyed nanoparticles with cobalt concentration of 0.18 M increases ~46% in comparison to that of 0.05 M. Direct to indirect energy band-gap transition is obtained when cobalt concentration goes beyond 0.05 M. A red shift in energy band gap is also observed for both the cases. Nanoparticles with low cobalt concentrations were found to have paramagnetic nature with no antiferromagnetic coupling. A negative Curie–Weiss temperature of −75 K with antiferromagnetic coupling was obtained for the high cobalt concentration.