Different Concentrations Of Cr Research Articles

Prosopis laevigata a potential chromium (VI) and cadmium (II) hyperaccumulator desert plant

The bioaccumulation of Cr(VI) and Cd(II) in Prosopis laevigata and the effect of these heavy metals on plant growth were assessed. P. laevigata seeds were cultured during 50days on modified Murashige–Skoog medium supplemented with four different concentrations of Cr(VI) (0–3.4mM) and Cd(II) (0–2.2mM), respectively. Heavy metals did not stop germination, but smaller plants with fewer leaves and secondary roots were produced. Seedlings showed an accumulation of 8176 and 21,437mg Cdkg−1 and of 5461 and 8090mg Cr kg−1 dry weight, in shoot and root, when cultured with 0.65mM Cd(II) and 3.4mM Cr(VI), respectively. These results indicated that significant translocation from the roots unto aerial parts took place. A bioaccumulation factor greater than 100 for Cd and 24 for Cr was exhibited by the seedlings. P. laevigata can be considered as a potential hyperaccumulator of Cd(II) and Cr(VI) species and considered as a promising candidate for phytoremediation purposes.

Chromium-induced biochemical, genotoxic and histopathologic effects in liver and kidney of goldfish, carassius auratus

Fish constitute an excellent model to understand the mechanistic aspects of metal toxicity vis-à-vis oxidative stress in aquatic ecosystems. Hexavalent chromium (Cr (VI)), due to its redox potential can induce oxidative stress (OS) in fish and impair their health. In the present investigation, we hypothesize that OS plays a key role in chromium induced toxicity in goldfish; leading to the production of reactive oxygen species (ROS) such as O(.)(2), H(2)O(2), OH(.), and subsequent modulation of the activities of antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), metallothioneins (MT), glutathione proxidase (GPx), genotoxicity and histopathology. To test this hypothesis, antioxidant enzymes, DNA damage and histopathology assays were performed in liver and kidney tissues of goldfish exposed to different concentrations of Cr (VI) (LC(12.5), LC(25) and LC(50)) following 96h static renewal bioassay. The results of this study clearly show that the fish experienced OS as characterized by significant modulation of enzyme activities, induction of DNA damage and microscopic morphological changes in the liver and kidney. In both tissues, CAT activity was decreased whereas SOD activity and hydroperoxide levels were increased. In addition, GPx activity also increased significantly in higher test concentrations, especially in the kidney. MT induction and DNA damage were observed in both tissues in a concentration dependent manner. Microscopic examination of organ morphology indicated degeneration of liver tissue and necrosis of central vein. Necrosis of kidney tubular epithelial cells and tubules was observed at higher Cr (VI) concentrations. Taking together the findings of this study are helpful in organ-specific risk assessment of Cr (VI)-induced oxidative stress, genotoxicity and histopathology in fish.

Cathodoluminescence microscopy and spectroscopy of synthetic ruby crystals grown by the optical floating zone technique

Synthetic rubies were grown by the optical floating zone method and characterized by cathodoluminescence (CL) microscopy and spectroscopy in combination with microprobe analysis. The measured intensity of the Cr 3+ -induced CL of corundum is influenced by different parameters such as the sample thickness and orientation, the intensity of the beam current, and the quality of the sample surface. Furthermore, the spectral distribution of the CL emission changes with different concentrations of Cr in the corundum structure. Due to these effects, it is usually not possible to estimate the Cr content directly by using the measured CL intensity. However, we have developed an indirect method that is not significantly affected by these parameters. By using intensity ratios instead of measured intensities, a level of quantification of Cr in natural and synthetic corundum is now possible. Our study shows that the intensity ratio between the N-line at 701.6 nm and the sideband maximum at 713.2 nm displays a nearly linear dependence on the Cr concentration from ca. 100-300 ppm up to ca. 1.1 mol% Cr 2 O 3 . These results give a possible approach to develop an optical-microscope-based CL spectroscopy for quantitative measurements of Cr in natural rubies and synthetic α-Al 2 O 3 materials.

Effects of chromium on seed germination, root elongation and coleoptile growth in six pulses

The ecotoxicological effects of Cr2+ on germination and early seedling growth of six pulses were investigated. Seeds of these plants were exposed to seven different concentrations of Cr (0–3.2 mM). The results indicated that root elongation and coleoptile growth of six pulse plants were more sensitive than seed germination for measurement of the toxic of Cr2+ pollutions. Different species show different levels of tolerance to Cr2+ pollution. Lablab purpureus and Glycine max are the most sensitive to Cr2+, their germination percentage, root and coleoptile length were significantly lower than other tested species, by contrast, Lathyrus odoratus and Dumasia villosa are the most resist species, their germination and seedling growth almost were not influenced by Cr2+ pollution significantly comparing the control. There were significantly negatively correlations between seedling growth and increasing concentration of Cr2+ for Glycine max, Vigna radiate and Lablab purpureus. The significantly negative correlations between germination and increasing concentration of Cr2+ were shown for Glycine max, Vigna radiate and V angularis.

Single crystals growth and absorption spectra of Cr 3+-doped Al 2−xIn x(WO 4) 3 solid solutions

The growth conditions of pure and Cr 3+-doped Al 2− x In x (WO 4) 3 single crystals, using top-seeded solution growth (TSSG) technique, have been studied. A series of experiments have been performed at different In concentrations, x=0.0, 0.3, 0.6 and 1.0, as well as at different concentrations of Cr 3+ (0.0, 0.1, 0.2, 0.5 and 1.0) in at% with respect to the initial total concentration of Al and In in the starting solutions. The basic parameters of the crystal growth are varied over a wide range: seed orientation, speed of rotation, axial and radial temperature differences in the solution and the solution cooling rate. The investigated relations between the basic defects in the crystals and these parameters result in determination of the optimal conditions for growth of defect-free crystals. Distribution coefficients of Al, In and Cr have been determined, so the growth of crystals with given compositions is possible. Values of Dq/ B (crystal field strength) for the various crystal compositions are calculated from the optical absorption spectra. The calculated values show that the discussed solid solutions have weak crystal field and are suitable for media with broadband emission spectra.

Chromium reduces the in vitro activity and fidelity of DNA replication mediated by the human cell DNA synthesome

Hexavalent chromium Cr(VI) is known to be a carcinogenic metal ion, with a complicated mechanism of action. It can be found within our environment in soil and water contaminated by manufacturing processes. Cr(VI) ion is readily taken up by cells, and is recognized to be both genotoxic and cytotoxic; following its reduction to the stable trivalent form of the ion, chromium(Cr(III)), within cells. This form of the ion is known to impede the activity of cellular DNA polymerase and polymerase-mediated DNA replication. Here, we report the effects of chromium on the activity and fidelity of the DNA replication process mediated by the human cell DNA synthesome. The DNA synthesome is a functional multiprotein complex that is fully competent to carry-out each phase of the DNA replication process. The IC 50 of Cr(III) toward the activity of DNA synthesome-associated DNA polymerases α, δ and ɛ is 15, 45 and 125 μM, respectively. Cr(III) inhibits synthesome-mediated DNA synthesis (IC 50 = 88 μM), and significantly reduces the fidelity of synthesome-mediated DNA replication. The mutation frequency induced by the different concentrations of Cr(III) ion used in our assays ranges from 2–13 fold higher than that which occurs spontaneously, and the types of mutations include single nucleotide substitutions, insertions, and deletions. Single nucleotide substitutions are the predominant type of mutation, and they occur primarily at GC base-pairs. Cr(III) ion produces a lower number of transition and a higher number of transversion mutations than occur spontaneously. Unlike Cr(III), Cr(VI) ion has little effect on the in vitro DNA synthetic activity and fidelity of the DNA synthesome, but does significantly inhibit DNA synthesis in intact cells. Cell growth and proliferation is also arrested by increasing concentrations of Cr(VI) ion. Our studies provide evidence indicating that the chromium ion induced decrease in the fidelity and activity of synthesome mediated DNA replication correlates with the genotoxic and cytotoxic effects of this metal ion; and promotes cell killing via inhibition of the DNA polymerase activity mediating the DNA replication and repair processes utilized by human cells.

Chromium(VI) Resistance and Extracellular Polysaccharide (EPS) Synthesis by Pseudomonas, Stenotrophomonas and Methylobacterium Strains

Microorganisms have great value in research, for multiple purposes during the last several decades. Resistance of various strains of microorganisms against chromium and the production of the extracellular polysaccharide (EPS) had been experimented and reveals the fact that the most of the strains (Pseudomonas, Stenotrophomonas, Methylobacterium) which produced high concentration of EPS shown resistance to Cr(VI). The most resistant Methylobacterium mesophilium MU141 (435 mg/L) secreted higher EPS than the rest of the strain. The toxic effect of Cr(VI) on cell viability and total cell protein of M. mesophilium MU 141 was treated by different concentration of Cr(VI), ranged from 15 and 35 ppm for 24 h. Hence, concentration of Cr(VI) can affect the EPS production at certain spectrum. Therefore, the result discloses the correlation between Cr(VI) resistance and EPS production among Pseudomonas, Stenotrophomonas, Methylobacterium strains.

Features of the local structural disorder in Li2O–CaF2–P2O5 glass–ceramics with Cr2O3 as nucleating agent

Abstract Li 2 O–CaF 2 –P 2 O 5 glasses mixed with different concentrations of Cr 2 O 3 (ranging from 0 to 1.0 mol%) were crystallized. The samples were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy (EDS), differential thermal analysis and conventional spectroscopic techniques. The X-ray diffraction and scanning electron microscopic studies reveal the presence of lithium phosphate, calcium phosphate and chromium phosphate (complexes of Cr 3+ , Cr 5+ and Cr 6+ ions) crystal phases. The study on DTA suggests that the crystallization is predominantly due to the surface crystallization when the concentration of nucleating agent Cr 2 O 3 is around 0.8 mol%. The IR and Raman spectral studies of these samples indicate that the sample crystallized with 0.8 mol% Cr 2 O 3 is more compact and possesses high rigidity due to the presence of chromium ions largely in tetrahedral positions.

Adsorption of chromium from aqueous solution using chitosan beads

A basic investigation on the removal of Cr(III) and Cr(VI) ions from aqueous solution by chitosan beads was conducted in a batch adsorption system. The chitosan beads were prepared by casting an acidic chitosan solution into an alkaline solution. The influence of different experimental parameters; pH, agitation period and different concentration of Cr(III) and Cr(VI) ions was evaluated. A pH 5.0 was found to be an optimum pH for Cr(III) adsorption, and meanwhile pH 3.0 was the optimum pH for the adsorption of Cr(VI) onto chitosan beads. The Langmuir and Freundlich adsorption isotherm models were applied to describe the isotherms and isotherm constants for the adsorption of Cr(III) and Cr(VI) onto chitosan beads. Results indicated that Cr(III) and Cr(VI) uptake could be described by the Langmuir adsorption model. The maximum adsorption capacities of Cr(III) and Cr(VI) ions onto chitosan beads were 30.03 and 76.92 mg g−1, respectively. Results showed that chitosan beads are favourable adsorbents. The Cr(III) and Cr(VI) ions can be removed from the chitosan beads by treatment with an aqueous EDTA solution.

Influence of plant growth promoting bacteria and Cr 6+ on the growth of Indian mustard

The Cr 6+ resistant plant growth promoting bacteria (PGPB), Pseudomonas sp. PsA4 and Bacillus sp. Ba32 were isolated from heavy metal contaminated soils and their plant growth promoting activity on the Indian mustard ( Brassica juncea) were assessed with different concentrations of Cr 6+ in soil. Production of siderophores and the solubilization of phosphate were observed in both strains, PsA4 and Ba32. Production of IAA was only observed in strain PsA4. Inoculation of PsA4 or Ba32 promoted the growth of plants at 95.3 and 198.3 μg of Cr 6+g −1 soil. The maximum growth was observed in the plants inoculated with strain PsA4. Both strains, PsA4 and Ba32 did not influence the quantity of accumulation of chromium in root and shoot system. The present observations showed that the strains PsA4 and Ba32 protect the plants against the inhibitory effects of chromium, probably due to the production of IAA, siderophores and solubilization of phosphate.

Tissue distribution, subcellular localization and endocrine disruption patterns induced by Cr and Mn in the crab Ucides cordatus

The essential trace elements Cr and Mn are toxic at high concentrations and information about low concentration is insufficient in the literature. In polluted mangroves, the crab Ucides cordatus can represent a useful tool to assess information on the potential impact of trace elements like Cr and Mn on the environment, since this species is comestible and thus, commercially negotiated. Therefore, U. cordatus crabs were exposed in vivo to different concentrations of Cr and Mn solved in seawater and had their tissue distribution and subcellular deposits evaluated. The gill, hepatopancreas and muscle concentrations were determined by atomic absorption spectroscopy and the results showed that Cr and Mn presented the highest values in the gills rather than in the hepatopancreas and muscular tissue. Electron microscopy and analytical X-ray microanalysis revealed Cr precipitates on the gill surface, co-localized with epiphyte bacteria. In addition, since Cr and Mn did not equally accumulate in most of the tissues studied, glycemic rate of animals, which received injections of extracts of eyestalks of the contaminated crabs, were measured in order to evaluate whether the studied concentrations of Cr and Mn could produce any metabolic alteration. The results indicated that extracts of the eyestalks of crabs submitted to Cr and Mn salts and injected into normal crabs markedly influenced crustacean hyperglycemic hormone synthesis and/or release. The results are discussed with respect to sensitivity of the employed methods and the possible significance of the concentrations of Cr and Mn in the organisms.

Effect of Organic Amendments on the Oxygen Uptake of Pseudomonas putida—PAPs-1 in Chromium-Contaminated Pond Ash

In this study a Cr (VI) resistant bacterium Pseudomonas putida was isolated from pond ash and its oxygen consumption potential at different concentrations of Cr (VI) viz., 0, 100 and 200 mg kg−1 was studied using Electrolytic Respirometry. Oxygen consumption by the bacterium was noticed up to 200 mg kg−1 Cr (VI) concentration. To the pond ash (inoculated with and without Pseudomonas) 200 mg kg−1 Cr (VI) was added and incorporated with different organic amendments such as farmyard manure (FYM), coir pith, paddy straw and press mud and the cumulative oxygen consumption was studied. The cumulative oxygen consumption by the bacterium was higher when the pond ash was incorporated with organic amendments. The highest oxygen consumption of 205 mg l−1 was observed when press mud was used, which was followed by FYM (198 mg l− 1 ). Furthermore, the enrichment with press mud increased the nutrient content of N (57.28 mg kg−1 ), P (5.5 mg kg−1 ) and K (42.7 mg kg−1 ) of the pond ash. The maximum dehydrogenase enzyme activity of 0.63 μ g TPF formed g−1 sample h−1 was measured when the pond ash was inoculated with Pseudomonas and enriched with press mud. The results also indicated that maximum reduction of Cr (VI) (42.5%) was observed when Pseudomonas and press mud were used. This study evaluated the possibilities of toxicity reduction and nutrient enrichment of the ash pond using a Cr (VI) resistant bacterium and organic amendments.

Tolerance and accumulation of hexavalent chromium by two seaweed associated aspergilli

Marine seaweed ( Eucheuma sp.) associated strains of Aspergillus flavus and Aspergillus niger were tested for their Cr(VI) tolerance. Both the isolates showed luxuriant growth in different concentrations of Cr(VI), i.e., 25, 50 and 100 ppm. There was no marked variation in the dry weight of control and test isolates, which indicated that both the isolates can tolerate a wide range of hexavalent chromium and their application for bioremediation purpose can be envisaged as XRF data revealed both the isolates accumulated more than 25% of the chromium supplied. A. flavus invariably exhibited higher accumulation potential.

The effect of Cr concentration on emission cross-section and fluorescence lifetime in Cr,Yb:YAG crystal

The emission cross-section, and fluorescence lifetime of Cr,Yb:YAG with different concentration of Cr 4+ and Yb:YAG were measured. With the increase of Cr concentration in Cr,Yb:YAG, the emission cross-section keeps constant and fluorescence lifetime decreases. The quantum efficiency decreases and the energy transfer efficiency from Yb 3+ to Cr 4+ increase as the Cr concentration increases in Cr–Yb-co-doped Cr,Yb:YAG system. The nonradiative Yb 3+→Cr 4+ energy transfer is consistent with an electric dipole–dipole interaction mechanism. The optimum Cr concentration for Cr,Yb:YAG was estimated. Also the potential of Cr,Yb:YAG as a self-Q-switched laser crystal was discussed.

Removal of Cr(VI) by solvent impregnated resins (SIR) containing aliquat 336

Solvent impregnated resins (SIR) have been prepared by a wet-impregnation technique using two different polymer matrices, Diaion HP-20 and HP-2MG. Diaion HP-20 possesses a hydrophobic styrene–divinylbenzene polymeric structure whereas HP-2MG is a hydrophilic methacrylic based polymer. Aliquat 336 was employed as the extractant and acetone as the solvent for impregnation. Batch sorption studies have shown that solvent impregnated resins containing Aliquat 336 can be effectively used for the removal of hexavalent chromium from aqueous solutions. The Langmuir adsorption isotherm gave a satisfactory fit of the equilibrium data. A kinetic study has been performed for SIR at two different concentrations of Cr(VI) (2×10 −4 and 4×10 −4 M). A finite-bath diffusion-control model with changing bulk concentration was used for sorption of Cr(VI) by SIR. Increasing the impregnation ratio from 0.5 to 1.0 (g Aliquat 336/g polymer adsorbent) increased the breakthrough capacity in a column-mode sorption study. The Cr(VI) bound by the SIR has been quantitatively desorbed using 0.1 M NaOH–0.1 M NaCl mixture.

Extraction and preconcentration of Cr(VI) from urine using supported liquid membrane

A supported liquid membrane (SLM) technique was investigated to extract and preconcentrate Cr(VI) from urine. Methyltricaprylammonium chloride (aliquat 366) with kerosene as diluent was used as a carrier in the membrane to transport Cr(VI) from the donor side to acceptor side. The membrane was modified with tri- n-butylphosphate (TBP) to increase its polarity. Various parameters were investigated to optimize the extraction efficiency: pH of the donor and acceptor phase, dilution factor, donor flow rate, boiling the sample and treatment with acetonitrile. Scanning electron microscope pictures of the membranes revealed that some matrix compounds were deposited on the surface, thus, limiting the extraction process. This was minimized by treatment of the urine sample with acetonitrile. The optimum conditions found were: pH 3 in the donor phase, sodium nitrate in the acceptor phase, donor flow rate of 0.3 ml min −1, 5% (w/v) aliquat in kerosene as a carrier in membrane, and 20 times the dilution factor. The extraction efficiency was found to be 15% with different concentrations of Cr(VI) standard addition extracted and shows that the method is highly reproducible. The adsorptive stripping voltammetry (AdSV) was used to determine Cr(VI) concentration. The optimized method was used to determine the concentration of Cr(VI) in urine samples of chromium smelter workers.

Reductive activation with cysteine represents a chromium(III)-dependent pathway in the induction of genotoxicity by carcinogenic chromium(VI).

Induction of DNA damage by carcinogenic hexavalent chromium compounds [Cr(VI)] results from its reduction to lower oxidation states. Reductive metabolism of Cr(VI) generates intermediate Cr(V/IV)species, organic radicals, and finally Cr(III), which forms stable complexes with many biological ligands, including DNA. To determine the biological significance of different reaction products, we examined genotoxic responses and the formation of DNA damage during reduction of Cr(VI) by its biological reducer, cysteine. We have found that cysteine-dependent activation of Cr(VI) led to the formation of Cr-DNA and cysteine-Cr-DNA adducts as well as interstrand DNA cross-links. The yield of binary and ternary DNA adducts was relatively constant at different concentrations of Cr(VI) and averaged approximately 54 and 45%, respectively. Interstrand DNA cross-links accounted on average for 1% of adducts, and their yield was even less significant at low Cr(VI) concentrations. Reduction of Cr(VI) in several commonly used buffers did not induce detectable damage to the sugar-phosphate backbone of DNA. Replication of Cr(VI)-modified plasmids in intact human fibroblasts has shown that cysteine-dependent metabolism of Cr(VI) resulted in the formation of mutagenic and replication-blocking DNA lesions. Selective elimination of Cr-DNA adducts from Cr(VI)-treated plasmids abolished all genotoxic responses, indicating that nonoxidative, Cr(III)-dependent reactions were responsible for the induction of both mutagenicity and replication blockage by Cr(VI). The demonstration of the mutagenic potential of Cr-DNA adducts suggests that these lesions can be explored in the development of specific and mechanistically important biomarkers of exposure to toxic forms of Cr.

Accumulation of chromium by Commelina communis L. grown in solution with different concentrations of Cr and L-histidine

Accumulation of chromium by Commelina communis L. grown in solution with different concentrations of Cr and L-histidine

Accumulation of chromium byCommelina communisL. grown in solution with different concentrations of Cr and L-histidine

Accumulation of chromium by<i>Commelina communis</i>L. grown in solution with different concentrations of Cr and L-histidine

Comparative studies on accumulation of Cr from metal solution and tannery effluent under repeated metal exposure by aquatic plants: its toxic effects.

The present study demonstrates comparison of Cr accumulating potential by the plants of Najas indica Cham. (submerged), Vallisneria spiralis L. (rooted submerged) and Alternanthera sessilis R. Br. (rooted emergent) under repeated metal exposure and its effect on chlorophyll and protein concentrations. These plants were treated with different concentrations of Cr under repeated exposure in controlled laboratory conditions to assess the maximum metal accumulation potential. The plants of V. spiralis accumulated significantly high amount of Cr under laboratory conditions in comparison to N. indica and A. sessilis. The maximum accumulation of 1378, 458 and 201 microg (-1) dw Cr was found in the leaves of V. spiralis. N. indica and A. sessilis, respectively at 8 mg (-1) after 9 day of Cr exposure. These plants have shown a decrease in chlorophyll and protein concentrations with increase in Cr concentrations. In view of high accumulation of Cr in V. spiralis, the plants were treated with different concentrations of tannery effluent collected from Common Effluent Treatment Plant, Unnao (UP). The plants of V. spiralis treated with 100% tannery wastewater showed the maximum accumulation (57.5 microg g(-1) dw) of Cr in the roots after 10 days of exposure. The plants were found effective in removing Cr from solution and tannery effluent.