Authors:J. Yao, F. Wang, L. Tian, Y. Zhou, H. Chen, K. Chen, N. Gai, R. Zhuang, T. Maskow, B. Ceccanti, and G. Zaray
Using TAM III multi-channel calorimetry combined with direct microorganism counting (bacteria, actinomycetes and fungi) under
laboratory conditions, we determined the microbial population count, resistance and activity toward cadmium (Cd(II)) and hexavalent
chromium (Cr(VI)) toxicity in soil. The thermokinetic parameters, which can represent soil microbial activity, were calculated
from power-time curves of soil microbial activity obtained by microcalorimetric measurement. Simultaneous application of the
two methods showed that growth rate constant (k), peak-heat output power (Pmax) and the number of living microorganisms decreased with increasing concentration of Cd and Cr. The accumulation of Cr on
E. coli was conducted by HPLC-ICP-MS. Cr6+ accumulation by Escherichia coli was increased steadily with increasing Cr6+ concentration. The results revealed that the change in some thermo-kinetic parameters could have good corresponding relationship
with metal accumulation. Our work also suggests that microcalorimetry is a fast, simple, more sensitive, on-line and in vitro
method that can be easily performed to study the toxicity of different species of heavy metals on microorganism compared to
other biological methods, and can combine with other analytic methods to study the interaction mechanism between environmental
toxicants and microbes.
Authors:Hedvig Fébel, B. Szegedi, and Szilvia Huszár
The intestinal absorption of trivalent and hexavalent chromium (Cr) given orally (experiment I) or infused in the intestine (experiment II) was investigated in rats. The nonabsorbable form of chromium (51Cr2O3) and water-soluble and more absorbable Na251CrO4 (the hexavalent form of Cr) were compared. Total retention of chromium given orally ranged around 15 percent of the dose, regardless of the chromium compounds applied. The absorption rate of chromic oxide, which is considered a nonabsorbable compound, was 14.4 as a percentage of chromium intake. This result indicates that some loss of chromium has to be taken into account in metabolic trials made by the indicator method. In isolated rat intestine, from the injected Cr 2.5% of chromic oxide and 43.2% of sodium chromate were absorbed during an hour (experiment II). The absorbed chromium was transferred to the liver where the liver tissue retained 10.9% of chromic oxide and 51.1% of sodium chromate. Radioactivity of v. cava caudalis following intestinal injection of Na2CrO4 was thirtyfold greater than after Na2CrO4 dosing. This phenomenon can be explained by the lower blood clearance of chromate. Different absorption rate of chromate depending on the route of administration could be due to the fact that the hexavalent form given orally was reduced to Cr3+ in the acidic environment of the stomach. When Na2CrO4 was infused directly in the intestine of rats, such reduction could not occur. This means that the acidic gastric juice might play a role in inhibiting the intestinal absorption of Na2CrO4 when this compound is given orally.
Authors:Yasemin Ozdener, Birsen Aydin, S. Fatma Aygün, and Füsun Yürekli
Liu, D., Zou, J., Wang, M., Jiang, W. (2008) Hexavalentchromium uptake and its effects on mineral uptake, antioxidant defence system and photosynthesis in Amaranthus viridis . Bioresour. Technol. 99 , 2628
The effect of different chromium [Cr(VI)] concentrations (0, 75, 150 and 225 μM) on dehydrogenase activity, total soluble protein, proline, malondialdehyde (MDA) and antioxidant enzymes was investigated in the roots of two barley cultivars (Cr-tolerant Zeynelağa and Cr-sensitive Orza-96) in hydroponic experiments. The root dehydrogenase activity and protein content decreased with an increase in the Cr(VI) concentration, but no significant difference was found between the two barley cultivars. Cr(VI) stress increased the contents of proline and MDA in both cultivars, but this effect was more pronounced in Orza-96 than in Zeynelağa. The activities of antioxidant enzymes, including superoxide dismutase (SOD), ascorbate peroxidase (APX) and guaiacol peroxidase (POD), exhibited changes. The SOD activity increased in Zeynelağa and decreased in Orza-96 at 225 μM Cr(VI) compared to their controls. Cr(VI) stress decreased the APX and POD activities. Zeynelağa had greater APX activity than Orza-96 at 150 and 225 μM Cr(VI). However, there was no marked difference in POD activities between the two cultivars. The decrease in root dehydrogenase activity and protein content, the increase in proline and lipid peroxidation, and the alterations in the activities of antioxidant enzymes may be indicative of oxidative stress induced by Cr(VI).
Authors:G. Solano, S. Katz, J. Holzbecher, and A. Chatt
Reference materials for the speciation and quantification of chromium in contaminated soils were prepared by impregnating diatomaceous earth with BaCrO4 and Cr2O3. The chronium concentrations of these materials were confirmed to be 200 mg/kg both by atomic absorption spectrometry and by instrumental neutron activation analysis, but monthly assays over two calendar quarters of the reference material impregnated with BaCrO4 revealed the hexavalent chromium was not stable in this matrix.
Chromium has been determined by isotope dilution in artificial standards and in standard alloys using the substoichiometric
principle. As a substoichiometric reaction the reduction of Cr(VI) to Cr(III) was used, followed by separation of these species
by coprecipitation of the trivalent chromium on a Ti(OH)4 precipitate. For amounts smaller than 1 μg the standard method had to be modified owing to spontaneous reduction of hexavalent
chromium in the solution. Interferences from other metals, if they occur, can be easily overcome. The method is simple and
Substoichiometric extraction of chromium with tetraphenylarsonium chloride (TPACl), tri-n-octylamine (TNOA), diethylammonium
diethyldithiocarbamate (DDDC) and ammonium pyrrolidinedithiocarbamate (APDC) was examined in detail. Chromium can be extracted
substoichiometrically in a pH range, which is 1.1–2.6 for the TPACl compound, 0.6–2.3 for the TNOA compound, 5.1–6.4 for the
DDCC chelate and 3.9–4.9 for the APDC chelate. Chromium in high-purity calcium carbonate, Orchard Leaves (NBS SRM-1571) and
Brewers Yeast (NBS SRM-1569) was determined by neutron activation analysis combined with substoichiometric extraction by DDDC
and APDC. The values of 2.0±0.02 ppm and 2.6±0.2 ppm were obtained for Brewers Yeast and Orchard Leaves, respectively. These
values were in good agreement with the values reported by NBS. The reaction mechanism and the reaction ratio between hexavalent
chromium and dithiocarbamate were also discussed.
A method is presented for the determination of chromium in sea-and fresh water. Chromium is concentrated on activated carbon
from neutral solution after a previous reduction of chromate with sodium sulfite at pH 1.5. The final determination of the
total chromium content is performed by instrumental neutron activation analysis. By preconcentration on activated carbon a
differentiation between tervalent and hexavalent chromium is possible. A separate determination of both species is not yet
feasible due to the high carbon blank and to the necessity of measuring the adsorption percentage on carbon. The lower limit
of determination, which depends on the value of the carbon blank, is 0.05 μg Cr·1−1 with a precision of 20%.
Authors:Lenka Palaščáková, Adriana Eštoková, Magdaléna Bálintová, and Aneta Petriláková
products (in Slovak), 2009.
Potgieter S. S., Panichev N., Potgieter J. H., Panicheva S. Determination of hexavalentchromium in South African cements and cement-related materials with electro-thermal atomic absorption