Different Concentrations Of Cr Research Articles

Adsorption of hexavalent chromium from aqueous solutions using Canadian peat and coconut fiber

Chromium compounds widely used in chemical processes are one of the biggest hazardous pollutants in industry effluents. The aim of the research is to investigate the role of the organic matter - Canadian Peat and coconut fiber in the removal processes of toxic chromium compounds from aqueous solutions. Characterization of organic matter has been carried out using scanning electron microscope with EDS, X-ray diffraction, Fourier transform infrared spectroscopy and BET measurements in order to analyze the surface and the porosity of the materials. In the study different concentrations of Cr have been investigated on the adsorption process and it has been found that maximum removal approximately 94% for coconut fiber and 91% for Canadian peat can be achieved in the lowest concentration equal to 25mg/dm3 after 72h. Langmuir, Freundlich and Temkin adsorption isotherm models have been used in order to describe the sorption parameters using the experimental data. Pseudo first, second order and Webber-Morris kinetics models have been verified to check the nature (chemical, physical) of Cr(VI) sorption on the materials. It has been found that pseudo-second order is the best fit for the adsorption what suggest that the process is of chemical nature. Regeneration of organic matter has been carried out by washing it with different eluents. Sodium citrate has the highest degree of chromium ions elution (53–65%). The removal efficiency was maintained for both materials after the elution process. Obtained results show that both organic materials can be effectively used for the removal of toxic chromium compounds from the aqueous solutions.

Effect of various concentrations of chromium polluted soil on biochemical changes of Globe amaranth (Gomphrena globosa L.)

An attempt was made to study the effect of different concentrations of chromium on biochemical specifications on response of Globe amaranth (Gomphrena globosa L.). The seeds were obtained from Private Agro centre, Villupuram District, Tamil Nadu, India. The healthy seeds of globe amaranth were chosen and used for both laboratory experiments. The various Cr concentrations were used (25, 50, 75 and 100 mg/l). Biochemical parameter such as, protein, amino acid, sugar and proline contents in leaf, stem and root of globe amaranth at 15, 30, 45 and 60 DAS in chromium polluted soil. Among the results protein, sugars and amino acid contents in leaf, stem and root were also significantly decreased in all different concentration of Cr treated as compared to control plants. On the other hand, proline content in leaf, stem and root were increased in all the Cr treated plants as compared to control. To sum up protein, sugars and amino acid were also significantly decreased while, proline content was increased in all the chromium treated plants.

Citric acid assisted phytoextraction of chromium by sunflower; morpho-physiological and biochemical alterations in plants

Soil and water contamination from heavy metals and metalloids is one of the most discussed and burning global issues due to its potential to cause the scarcity of healthy food and safe water. The scientific community is proposing a range of lab and field based physical, chemical and biological solutions to remedy metals and metalloids contaminated soils and water. The present study finds out a possibility of Chromium (Cr) extraction by sunflower from spiked soil under chelating role of citric acid (CA). The sunflower plants were grown under different concentrations of Cr (0, 5, 10 & 20mgkg−1) and CA (0, 2.5 & 5mM). Growth, biomass, gas exchange, photosynthesis, electrolyte leakage (EL), reactive oxygen species (ROS; malondialdehyde (MDA), hydrogen peroxide (H2O2) and the activities of antioxidant enzymes such as, superoxide dismutase (SOD), guaiacole values peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT) were measured. The results depicted a clear decline in plant height, root length, leaf area, number of leaves and flowers per plant along with fresh and dry biomass of all parts of plant with increasing concentration of Cr in soil. Similar reduction was observed in chlorophyll a and b, total chlorophyll, carotenoids, soluble protein, gas exchange attributes and SPAD. The increasing concentration of Cr also enhanced the Cr uptake and accumulation in plant roots, stem and leaves along with the production of ROS and EL. The activities of antioxidant enzymes increased with increasing Cr concentration from 0 to 10mg, but decreased at 20mgkg−1 soil. The CA application significantly alleviated Cr-induced inhibition of plant growth, biomass, photosynthesis, gas exchange, soluble proteins and SPAD value. Presence of CA also enhanced the activities of all antioxidant enzymes and reduced the production of ROS and EL. The chelating potential of CA increased the concentration and accumulation of Cr in plant roots, stem and leaves. It is concluded that the sunflower can be a potential candidate for the remediation of Cr under CA treatment, while the possibility may vary with genotype, Cr level and CA concentration.

Citric acid enhanced the antioxidant defense system and chromium uptake by Lemna minor L. grown in hydroponics under Cr stress.

Phytoextraction is a cost-effective and eco-friendly technique for the removal of pollutants, mainly heavy metal(loids) especially from polluted water and metal-contaminated soils. The phytoextraction of heavy metals is, in general, limited due to the low availability of heavy metals in the growth medium. Organic chelators can help to improve the phytoextraction by increasing metal mobility and solubility in the growth medium. The present research was carried out to examine the possibility of citric acid (CA) in improving chromium (Cr) phytoextraction by Lemna minor (duckweed). For this purpose, healthy plants were collected from nearby marsh and grown in hydroponics under controlled conditions. Initial metal contents of both marsh water and plant were measured along with physico-chemical properties of the marsh water. Different concentrations of Cr and CA were applied in the hydroponics in different combinations after defined intervals. Continuous aeration was supplied and pH maintained at 6.5±0.1. Results showed that increasing concentration of Cr significantly decreased the plant biomass, photosynthetic pigments, leaf area, and antioxidant enzyme activities (like catalase, ascorbate peroxidase, superoxide dismutase, peroxidase). Furthermore, Cr stress increased the Cr concentrations, electrolyte leakage, hydrogen peroxide, and malondialdehyde contents in plants. The addition of CA alleviated the Cr-induced toxicity in plants and further enhanced the Cr uptake and its accumulation in L. minor. The addition of CA enhanced the Cr concentration in L. minor by 6.10, 26.5, 20.5, and 20.2% at 0, 10, 100, and 200μM Cr treatments, respectively, compared to the respective Cr treatments without CA. Overall, the results of the present study showed that CA addition may enhance the Cr accumulation and tolerance in L. minor by enhancing the plant growth and activities of antioxidant enzymes.

Phyto-management of Cr-contaminated soils by sunflower hybrids: physiological and biochemical response and metal extractability under Cr stress.

Chromium (Cr) is a biologically non-essential, carcinogenic and toxic heavy metal. The cultivation of Cr-tolerant genotypes seems the most favorable and environment friendly strategy for rehabilitation and remediation of Cr-contaminated soils. To prove this hypothesis and identify the Cr tolerance, the present study was performed to assess the physiological and biochemical response of sunflower genotypes to Cr stress. The seeds of six sunflower hybrids, namely FH-425, FH-600, FH-612, FH-614, FH-619, and FH-620, were grown in spiked soil for 12weeks under increasing concentrations of Cr (0, 5, 10, and 20mgkg-1). A seed germination test was also run under different concentrations of Cr (0, 5, 10, 200 mM) in petri dishes. Plants were harvested after 12 weeks of germination. Different plant attributes such as growth; biomass; photosynthesis; gas exchange; activity of antioxidant enzymes, i.e., superoxide dismutase (SOD), guaiacol peroxidase (POD), ascorbate (APX), and catalases (CAT); reactive oxygen species (ROS); lipid peroxidation; electrolyte leakage; and Cr concentration as well as accumulations in all plant parts were studied for the selection of the most Cr-tolerant genotype. Increasing concentration of Cr in soil triggered the reduction of all plant parameters in sunflower. Cr stress increased electrolyte leakage and production of reactive oxygen species which stimulated the activities of antioxidant enzymes and gas exchange attributes of sunflower. Chromium accumulation in the root and shoot increased gradually with increasing Cr treatments and caused reduction in overall plant growth. The accumulation of Cr was recorded in the order of FH-614 > FH-620 > FH-600 > FH-619 > FH-612 > FH-425. The differential uptake and accumulation of Cr by sunflower hybrids may be useful in selection and breeding for Cr-tolerant genotypes.

Determination of hexavalent chromium concentration in industrial waste incinerator stack gas by using a modified ion chromatography with post-column derivatization method

An ion chromatography with post-column derivatization with 1,5-diphenylcarbazide (IC-DPC) analytical method was modified to enable measurement of trace-level hexavalent chromium (Cr(VI)) in air. One of the difficulties in determining trace levels of Cr(VI) in air with conventional IC-DPC methods is co-elution of the solvent and ion peaks due to high concentrations of ionic compounds in the extract. However, by using gradient elution rather than isocratic elution we were able to fully resolve the Cr(VI) ion peak from the solvent peak without the need for diluting the extract, which would have reduced the minimum quantifiable level of the method. With this method, we were able to detect Cr(VI) in air at concentrations of 5.3ng/m3 (assuming a sampling volume of 1m3 and a final solution volume of 10mL). Recovery tests at three different concentrations of Cr(VI) (50, 250, 1000ng) were performed with or without fly ash; recovery rates at all the concentrations of Cr(VI), with or without fly ash, ranged from 68% to 110% (mean±relative standard deviation, 96%±11%), and there were no differences in recovery rates with respect to the presence or absence of fly ash. Finally, we used the developed method to determine the concentration of Cr(VI) in stack gases collected from eight industrial waste incinerators located in Japan. The concentration of Cr(VI) in the stack gases ranged from below the method quantification limit to 3100ng/m3. The highest concentrations of Cr(VI) detected in the stack gases were two to three orders of magnitude higher than that in ambient air in Japan.

FUNGICIDAL POTENTIAL OF ALLELOPATHIC WEED Cenchrus pennisetiformis ON GROWTH OF Fusarium oxysporum f. sp. lycopersici UNDER CHROMIUM STRESS

ABSTRACT The present study was conducted to assess antifungal potential of the allelopathic grass Cenchrus pennisetiformis Hochst. & Steud. against the fungal plant pathogen Fusarium oxysporum f. sp. lycopersici (cause of tomato wilt disease) under chromium stress. Laboratory experiments were performed in 10 mL volume glass test tubes each containing 1.0 mL of malt extract broth with seven concentrations (0, 50, 100, 150, 200, 250, 300 and 350 ppm) of each of Cr(III) and Cr(VI), and two concentrations (5% and 6%) of methanolic leaf, stem or root extract of C. pennisetiformis. A metal + weed extract amended medium was inoculated with the pathogen and incubated for 7 days at 25 C. Different concentrations of Cr(III) and Cr(VI) proved equally inhibitory resulting in 10-84% and 18-89% reduction in fungal biomass, respectively. Methanolic leaf, stem and root extracts of the weed reduced fungal biomass by 12-25%, 14-23% and 46-50%, respectively, over negative control. In combined application of methanolic extracts of different parts of C. pennisetiformis and metal solutions, root extract in combination with either Cr(III) or Cr(VI) showed the highest inhibitory potential against the fungus followed by leaf and stem extracts. In combination with methanolic root, leaf and stem extracts, different concentrations of Cr(III) and Cr(VI) significantly reduced fungal biomass by 54-99%, 14-99% and 9-95%, respectively, over negative control. Such studies have not been carried out previously. Results of the present investigation suggest that F. oxysporum oxysporum f. sp. lycopersici, the cause of Fusarium wilt disease in tomato, can be managed by application of extracts (or alternatively biomass) of C. pennisetiformis in chromium contaminated soils.

Characterization of Chromium Waste Form Based on Biocementation by Microbacterium sp. GM-1.

This paper demonstrated a biocementation technology for chromium slag by strain GM-1, a calcifying ureolytic bacterium identified as Microbacterium, based on microbially induced calcium carbonate. The characterization of Microbacterium sp. GM-1 was assessed to know the growth curve in different concentrations of Cr(VI). Microbacterium sp. GM-1 was tolerant to a concentration of 120mg/L Cr(VI). Chromium waste forms were prepared using chromium, sand, soil and bacterial culture. There we had three quality ratios (8:2:1; 8:1:1; 8:2:0.5) of material (chromium, sand and soil, respectively). Bacterial and control chromium waste forms were analyzed by thermal gravimetric analyzer. All bacterial forms (8:2:1; 8:1:1; 8:2:0.5J) showed sharp weight loss near the decomposition temperature of calcium carbonate between 600 and 700°C. It indicated that the efficient bacterial strain GM-1 had induced calcium carbonate precipitate during bioremediation process. A five step Cr(VI) sequential extraction was performed to evaluate its distribution pattern in chromium waste forms. The percentage of Cr(VI) was found to significantly be decreased in the exchangeable fraction of chromium waste forms and subsequently, that was markedly increased in carbonated fraction after biocementation by GM-1. Further, compressive strength test and leaching test were carried out. The results showed that chromium waste forms after biocementation had higher compressive strength and lower leaching toxicity. Additionally, the samples made of 8:1:1 (m/m/m) chromium+sand+soil were found to develop the highest compressive strength and stand the lowest concentration of Cr(VI) released into the environment.

Two-body abrasion resistance of cementite containing different chromium concentrations

Abstract

Isolation and Identification of Chromium (VI)-Resistant Bacteria From Soltan Abad River Sediments (Shiraz-Iran)

Background: Chromium (Cr) is an important heavy metal widely used in industries. It is one of the seventeen chemicals with the highest danger to human health according to the United States environmental protection agency (USEPA). Objectives: The aim of this study was to isolate and identify Cr (VI)-resistant bacteria from Soltan Abad River sediments (Shiraz-Iran) and evaluate their potential for the detoxification of Cr (VI) to Cr (III) under environmental conditions. Materials and Methods: Bacterial isolates were identified on the basis of colony morphology, Gram staining, and biochemical tests using standard microbiological methods. The minimum inhibitory concentrations (MICs) of chromium were determined by the broth agar dilution method. Cr (VI) reduction assay was determined by measuring the absorbance of the purple complex of Cr (VI) with 1,5-diphenylcarbazide. The growth of Cr (VI)-resistant bacteria was determined at different concentrations of Cr (VI). Finally, the effects of temperature and pH on the growth of selected bacteria and Cr (VI) reduction were investigated using an Luria-Bertani (LB) medium containing 50 mg/L Cr (VI). Results: The results indicated that Pseudomonas aeruginosa and Serratia marcescens were the most resistant bacteria with MICs of 200 and 150 mg/L, respectively. Both bacteria completely reduced 25 and 50 mg/L of Cr (VI) in 36 hours and 48 hours, respectively. The growth rate of both bacteria decreased with increases in the Cr (VI) concentration, and the chromate reduction was directly correlated with the growth of the bacteria. These bacteria were capable of reducing Cr (VI) at a wide range of temperatures (25 to 45°C) and pH levels (5 to 9). The optimum medium conditions for Cr (VI) reduction and the growth of the isolates were temperatures between 30 and 40°C and a pH of 7.0 to 8.0. Conclusions: P. aeruginosa and S. marcescens can be good candidates for the detoxification of Cr (VI) in Soltan Abad River.

Effect of ethylene diamine tetra acetic acid chelator in the presence of chromium on growth and some physiological characteristics of sunflower.

Chromium is a heavy metal toxic for plants that due extensive industrial applications over the last decade, has become a serious environmental pollution. On the other hand, chelator dissolution and absorption of metal by the plant increase and their use in phytoremediation is important. The aim of this study was to evaluate the effect of different concentrations of chromium and ethylene diamine tetra acetic acid (EDTA) chelator on sunflower (Heliantus annuus L.) through the study of growth parameters, chlorophyll, and soluble sugar amounts and Cr accumulation in plants under hydroponic culture. In order to plant sunflower were treated with different concentrations of Cr (1, 2, 4 and 6 ppm) and EDTA (0, 1 and 3 mg/L) in the medium Hoagland. The results showed that the use of chromium reduced the length of shoots and roots, and chlorophyll, while it increased soluble sugars. Addition of EDTA to the metal increased the shoot and root length and chlorophyll content while it reduced soluble sugars. According to the results, the use of chromium heavy metal in medium increased the amount of it in shoot and root. EDTA application, particularly with higher levels of chromium led to its accumulation in shoot and root. This research suggested positive role of application of EDTA in the presence of chromium heavy metal in increasing the power of phytoremediation of sunflower.

Diminution of Oxidative Damage to Human Erythrocytes and Lymphocytes by Creatine: Possible Role of Creatine in Blood.

Creatine (Cr) is naturally produced in the body and stored in muscles where it is involved in energy generation. It is widely used, especially by athletes, as a staple supplement for improving physical performance. Recent reports have shown that Cr displays antioxidant activity which could explain its beneficial cellular effects. We have evaluated the ability of Cr to protect human erythrocytes and lymphocytes against oxidative damage. Erythrocytes were challenged with model oxidants, 2, 2'-azobis(2-amidinopropane) dihydrochloride (AAPH) and hydrogen peroxide (H2O2) in the presence and absence of Cr. Incubation of erythrocytes with oxidant alone increased hemolysis, methemoglobin levels, lipid peroxidation and protein carbonyl content. This was accompanied by decrease in glutathione levels. Antioxidant enzymes and antioxidant power of the cell were compromised while the activity of membrane bound enzyme was lowered. This suggests induction of oxidative stress in erythrocytes by AAPH and H2O2. However, Cr protected the erythrocytes by ameliorating the AAPH and H2O2 induced changes in these parameters. This protective effect was confirmed by electron microscopic analysis which showed that oxidant-induced cell damage was attenuated by Cr. No cellular alterations were induced by Cr alone even at 20 mM, the highest concentration used. Creatinine, a by-product of Cr metabolism, was also shown to exert protective effects, although it was slightly less effective than Cr. Human lymphocytes were similarly treated with H2O2 in absence and presence of different concentrations of Cr. Lymphocytes incubated with oxidant alone had alterations in various biochemical and antioxidant parameters including decrease in cell viability and induction of DNA damage. The presence of Cr attenuated all these H2O2-induced changes in lymphocytes. Thus, Cr can function as a blood antioxidant, protecting cells from oxidative damage, genotoxicity and can potentially increase their lifespan.

Alleviation of toxic hexavalent chromium using indigenous aerobic bacteria isolated from contaminated tannery industry sites

ABSTRACTIn the last decade, much attention has been paid to bioremediation of Cr(VI) using various bacterial species. Cr(VI) remediation by indegeneous bacteria isolated from contaminated sites of a tannery industry located in Tamil Nadu, India, was investigated in this study. Three Cr(VI) resistant bacterial strains (TES-1, TEf-1, and TES-2) were isolated and selected based on their Cr(VI) reduction ability in minimal salt medium. Among these three bacterial strains, TES-1 was found to be most efficient in bioreduction, while TES-2 was only found to be Cr(VI) resistant and showed negligible bioreduction, whereas TEf-1 was observed to be most Cr(VI) tolerant. Potential for bioremediation of TES-1 and TEf-1 was further investigated at different concentrations of Cr(VI) in the range of 50 to 350 mg L−1. TEf-1 showed prominent synchronous growth throughout the experiment, whereas TES-1 took a longer acclimatization time. Minimum inhibitory concentrations (MIC) of Cr(VI) for TES-1 and TEf-1 were approximated as 600 mg L−1 and 750 mg L−1, respectively. The kinetic behavior of Cr(VI) reduction by TES-1 and TEf-1 exhibited zero- and first-order removal kinetics for Cr(VI), respectively. The most efficient strain TES-1 was identified as Streptomyces sp. by gene sequencing of 16S rRNA.

Application of freeze desalination for chromium (VI) removal from water

Chromium (VI) is a highly toxic metal ion found in the priority list of pollutants, which is also often abundant in areas having low access to high-tech solutions for chromium (Cr) removal. This study was initiated to investigate the capacity of home-use refrigerators to generate fresh water free from Cr(VI) by melting ice produced from Cr(VI) polluted water. Simulated tap water samples as well as deionized water to which different concentrations of Cr(VI) were added were frozen in a closed freezer unit. The effects of initial concentration, time of ice nucleation, fraction of ice volume, and influence of co-occurring ions were evaluated in relation to the quality of the produced ice. The physicochemical characteristics of the produced ice cubes were also evaluated. A high total water recovery of up to 85% was achieved. Chromium removal ranged from 57.4 to 80% for simulated tap and from 93 to 97% for deionized water spiked with Cr. The energy consumption estimation basing form the refrigerator amounted to 0.076kWh. Freeze desalination was found to be relatively viable desalination technology in terms of quality of water produced, easiness for safe water production, and amount of energy consumed, especially where high-tech solutions for Cr(VI) removal are not available.

Kinetics of bioreduction of hexavalent chromium by poly vinyl alcohol-alginate immobilized cells of Ochrobactrum sp. Cr-B4 and comparison with free cells

The cells of Ochrobactrum sp. Cr-B4 immobilized in PVA-alginate blended matrix could be successfully used for bioreduction of Cr(VI) from contaminated water. The removal mechanism included adsorption on solid-liquid interface and enzyme catalyzed chromate reduction. At lower concentrations the initial rate of Cr(VI) reduction with immobilized cells was found to be slightly higher than that of free cells owing to adsorption on the immobilization matrix. But after a certain time the rate of Cr(VI) reduction by free and immobilized cells was similar. The estimation of effectiveness factor (η), indicated that there were no diffusional limitations offered by the immobilization of Cr-B4 as the value of η was fond to be near “one” at different concentrations of Cr(VI). The kinetic analysis showed that both free and immobilized cells followed Michaelis–Menten kinetics with Km and Vmax of 456.1 mg/L and 14.67 mg/L/h for free cells respectively; 499.4 mg/L and 15.32 mg/L/h for immobilized cells respectively. The kinetic characteristics of Cr(VI) reduction were not altered by immobilization. This study reveals the potential applications of immobilized Cr-B4 in development of industrially feasible and economically viable bioremediation strategy for discharging Cr(VI) free effluent into the environment.

Versatility of Streptomyces sp. M7 to bioremediate soils co-contaminated with Cr(VI) and lindane

The aim of this work was to study the impact of environmental factors on the bioremediation of Cr(VI) and lindane contaminated soil, by an actinobacterium, Streptomyces sp. M7, in order to optimize the process.Soil samples were contaminated with 25µgkg−1 of lindane and 50mgkg−1 of Cr(VI) and inoculated with Streptomyces sp. M7. The lowest inoculum concentration which simultaneously produced highest removal of Cr(VI) and lindane was 1gkg−1. The influence of physical and chemical parameters was assessed using a full factorial design. The factors and levels tested were: Temperature: 25, 30, 35°C; Humidity: 10%, 20%, 30%; Initial Cr(VI) concentration: 20, 50, 80mgkg−1; Initial lindane concentration: 10, 25, 40µgkg−1.Streptomyces sp. M7 exhibited strong versatility, showing the ability to bioremediate co-contaminated soil samples at several physicochemical conditions. Streptomyces sp. M7 inoculum size was optimized. Also, it was fitted a model to study this process, and it was possible to predict the system performance, knowing the initial conditions. Moreover, optimum temperature and humidity conditions for the bioremediation of soil with different concentrations of Cr(VI) and lindane were determined. Lettuce seedlings were a suitable biomarker to evaluate the contaminants mixture toxicity. Streptomyces sp. M7 carried out a successful bioremediation, which was demonstrated through ecotoxicity test with Lactuca sativa.

Chromium toxicity tolerance of Solanum nigrum L. and Parthenium hysterophorus L. plants with reference to ion pattern, antioxidation activity and root exudation

Chromium (Cr), being a highly toxic metal, adversely affects the mineral uptake and metabolic processes in plants when present in excess. The current study was aimed at investigating the Cr accumulation in various plant tissues and its relation to the antioxidation activity and root exudation. Plants were grown in soil spiked with different concentrations of Cr for three weeks in pots and analysed for different growth, antioxidants and ion attributes. Furthermore, plants treated with different concentrations of Cr in pots were shifted to rhizobox-like system for 48h and organic acids were monitored in the mucilage dissolved from the plant root surface, mirroring rhizospheric solution. The results revealed that the Cr application at 1mM increased the shoot fresh and dry weight and root dry weight of Solanum nigrum, whereas the opposite was observed for Parthenium hysterophorus when compared with lower levels of Cr (0.5mM) or control treatment. In both plant species, Cr and Cl concentrations were increased while Ca, Mg and K concentrations in root, shoot and root exudates were decreased with increasing levels of Cr. Higher levels of Cr treatments enhanced the activities of SOD, POD and proline content in leaves of S. nigrum, whereas lower levels of Cr treatment were found to have stimulatory effects in P. hysterophorus. P. hysterophorus exhibited highest exudation of organic acid contents. With increasing levels of Cr treatments, citric acid concentration in root exudates increased by 35% and 44% in S. nigrum, whereas 20% and 76% in P. hysterophorus. Cr toxicity was responsible for the shoot growth reduction of S. nigrum and P. hysterophorus, however, shoot growth response was different at different levels of applied Cr. Consequently, Cr stress negatively altered the plant physiology and biochemistry. However, the enhanced antioxidant production, Cl uptake and root exudation are the physiological and biochemical indicators for the plant adaptations in biotic systems polluted with Cr.

Mechanical properties, sliding wear and solid particle erosion behaviors of plasma enhanced magnetron sputtering CrSiCN coating systems

CrSiCN coating systems with different concentrations of Cr, Si, C, and N were investigated for their microstructure, mechanical properties (hardness H, elastic modulus E and indentation fracture toughness KIC) and tribological behaviors using SEM, nano-indentation, indentation, pin-on-disk wear test, and sand particle erosion test. The wear behaviors, such as specific wear rate and Archard wear coefficient, showed inverse relationships with H3/E2 ratio, confirming that the resistance to plastic deformation is the essential factor governing sliding wear behavior. High H3/E2 ratios also contributed to increased resistances to erosion at low impingement angles. However, at higher impingement angles (>60°), coatings with lower index of brittleness (B=2.656µm−1/2), higher critical load (P⁎=6.670N) for crack initiation and fracture surface energy (γf=0.123Jm−2) offered a higher erosion resistance. The indentation fracture toughness (KIC), hardness (H) and elastic modulus (E) are limited to interpret erosion behaviors in a comprehensive approach, suggesting that erosion is a complex process where multiple mechanical properties contribute to erosion performance.

Physiological and genetic effects of chromium (+VI) on toxitolerant lichen species, Pyxine cocoes.

Chromium is a highly toxic non-essential metal, which causes a variety of metabolic activities in plants. Pyxine cocoes a well known toxitolerant lichen species was considered to evaluate the possible physiological, biochemical, and genetic changes that occur due to chromium Cr (+VI) stress. The physiological (chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, protein, and Fv/Fm) and genetic (ISSR-PCR and ITS) parameters were used to estimate the changes in P. cocoes. Different concentrations of Cr (+VI) (0, 10, 25, 50, 75, and 100 μM) for 10, 20, 30, and 45 days were employed on transplanted lichen species. The results revealed that the exposure of Cr (+VI) for 10, 20, 30, and 45 days under controlled conditions caused a significant decline in physiological processes with increasing metal stress. Amino acid profile at different concentrations on the 45th day too indicated prevailing stress condition as proline content significantly increased at 100 μM concentration. Inter-simple sequence repeat (ISSR) and internal transcribed spacer (ITS) techniques were used to evaluate the genotoxicity induced by chromium stress. ISSR profiles showed a consistent increase in appearance and disappearance of bands with increasing concentration of the chromium. ISSR technique, therefore, is more sensitive and reproducible to study polymorphism induced by environmental stress. The present study revealed that the physiological and genetic changes induced by the Cr (+VI) can be used as a tool to study environmental stress and polymorphisms due to genotoxicity. To the best of our knowledge, application of ISSR-PCR and ITS sequences in toxitolerant species (P. cocoes) appears to be the maiden attempt to evaluate the genotoxicity.

N-Acetylcysteine Attenuates Hexavalent Chromium-Induced Hypersensitivity through Inhibition of Cell Death, ROS-Related Signaling and Cytokine Expression

Chromium hypersensitivity (chromium-induced allergic contact dermatitis) is an important issue in occupational skin disease. Hexavalent chromium (Cr (VI)) can activate the Akt, Nuclear factor κB (NF-κB), and Mitogen-activated protein kinase (MAPK) pathways and induce cell death, via the effects of reactive oxygen species (ROS). Recently, cell death stimuli have been proposed to regulate the release of inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1). However, the exact effects of ROS on the signaling molecules and cytotoxicity involved in Cr(VI)-induced hypersensitivity have not yet been fully demonstrated. N-acetylcysteine (NAC) could increase glutathione levels in the skin and act as an antioxidant. In this study, we investigated the effects of NAC on attenuating the Cr(VI)-triggered ROS signaling in both normal keratinocyte cells (HaCaT cells) and a guinea pig (GP) model. The results showed the induction of apoptosis, autophagy and ROS were observed after different concentrations of Cr(VI) treatment. HaCaT cells pretreated with NAC exhibited a decrease in apoptosis and autophagy, which could affect cell viability. In addition, Cr (VI) activated the Akt, NF-κB and MAPK pathways thereby increasing IL-1α and TNF-α production. However, all of these stimulation phenomena could be inhibited by NAC in both of in vitro and in vivo studies. These novel findings indicate that NAC may prevent the development of chromium hypersensitivity by inhibiting of ROS-induced cell death and cytokine expression.