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Posts Tagged ‘Cromium’

 

Copper isotope fractionation during its interaction with soil

and aquatic microorganisms and metal oxy(hydr)oxides:

Possible structural control

O.S. Pokrovsky a,*, J. Viers a, E.E. Emnova b, E.I. Kompantseva c, R. Freydier a

a Laboratoire de Me´canismes et Transfert en Ge´ologie (LMTG), Universite´ de Toulouse, CNRS, IRD,

OMP, 14 Avenue Edouard Belin, 31400 Toulouse, France

b Institute of Genetics and Plant Physiology, Moldavian Academy of Science, Kishinev, Moldavia

c Institute of Microbiology, Russian Academy of Science, Moscow, Russia

Received 4 June 2007; accepted in revised form 23 January 2008; available online 31 January 2008

Pdf Abastract This work is aimed at quantifying the main environmental factors controlling isotope fractionation of Cu during its adsorption from aqueous solutions onto common organic (bacteria, algae) and inorganic (oxy(hydr)oxide) surfaces. Adsorption of Cu on aerobic rhizospheric (Pseudomonas aureofaciens CNMN PsB-03) and phototrophic aquatic (Rhodobacter sp. f-7bl, Gloeocapsa sp. f-6gl) bacteria, uptake of Cu by marine (Skeletonema costatum) and freshwater (Navicula minima, Achnanthidium minutissimum and Melosira varians) diatoms, and Cu adsorption onto goethite (FeOOH) and gibbsite (AlOOH) were studied using a batch reaction as a function of pH, copper concentration in solution and time of exposure. Stable isotopes of copper in selected filtrates were measured using Neptune multicollector ICP-MS. Irreversible incorporation of Cu in cultured diatom cells at pH 7.5–8.0 did not produce any isotopic shift between the cell and solution (D65/63Cu(solid-solution)) within ±0.2&. Accordingly, no systematic variation was observed during Cu adsorption on anoxygenic phototrophic bacteria (Rhodobacter sp.), cyanobacteria (Gloeocapsa sp.) or soil aerobic exopolysaccharide (EPS)-producing bacteria (P. aureofaciens) in circumneutral pH (4–6.5) and various exposure times (3 min to 48 h): D65Cu(solid-solution) = 0.0 ± 0.4&. In contrast, when Cu was adsorbed at pH 1.8–3.5 on the cell surface of soil the bacterium P. aureofacienshaving abundant or poor EPS depending on medium composition, yielded a significant enrichment of the cell surface in the light isotope (D65Cu (solid-solution) = _1.2 ± 0.5&). Inorganic reactions of Cu adsorption at pH 4–6 produced the opposite isotopic offset: enrichment of the oxy(hydr)oxide surface in the heavy isotope with D65Cu(solid-solution) equals 1.0 ± 0.25& and 0.78 ± 0.2& for gibbsite and goethite, respectively. The last result corroborates the recent works of Mathur et al. [Mathur R., Ruiz J., Titley S., Liermann L., Buss H. and Brantley S. (2005) Cu isotopic fractionation in the supergene environment with and without bacteria. Geochim. Cosmochim. Acta 69, 5233–5246] and Balistrieri et al. [Balistrieri L. S., Borrok D. M., Wanty R. B. and Ridley W. I. (2008) Fractionation of Cu and Zn isotopes during adsorption onto amorhous Fe(III) oxyhydroxide: experimental mixing of acid rock drainage and ambient river water. Geochim. Cosmochim. Acta 72, 311–328] who reported heavy Cu isotope enrichment onto amorphous ferric oxyhydroxide and on metal hydroxide precipitates on the external membranes of Fe-oxidizing bacteria, respectively. Although measured isotopic fractionation does not correlate with the relative thermodynamic stability of surface complexes, it can be related to their structures as found with available EXAFS data. Indeed, strong, bidentate, inner-sphere complexes presented by tetrahedrally coordinated Cu on metal oxide surfaces are likely to result in enrichment of the heavy isotope on the surface compared to aqueous solution. The outer-sphere, monodentate complex, which is likely to form between Cu2+ and surface phosphoryl groups of bacteria in acidic solutions, has a higher number of neighbors and longer bond distances compared to inner-sphere bidentate complexes with carboxyl groups formed on bacterial and diatom surfaces in circumneutral solutions. As a result, in acidic solution, light isotopes become more enriched on bacterial surfaces (as opposed to the surrounding aqueous medium) than they do in neutral solution. Overall, the results of the present study demonstrate important isotopic fractionation of copper in both organic and inorganic systems and provide a firm basis for using Cu isotopes for tracing metal transport in earth-surface aquatic systems. It follows that both adsorption on oxides in a wide range of pH values and adsorption on bacteria in acidic solutions are capable of producing a significant (up to 2.5–3& (±0.1–0.15&)) isotopic offset. At the same time, Cu interaction with common soil and aquatic bacteria, as well as marine and freshwater diatoms, at 4 < pH < 8 yields an isotopic shift of only ±0.2–0.3&, which is not related to Cu concentration in solution, surface loading, the duration of the experiment, or the type of aquatic microorganisms.

Biosorption of Cr(VI) by immobilized biomass of two indigenous

strains of cyanobacteria isolated from metal contaminated soil

Kamra Anjana, Anubha Kaushik , Bala Kiran, Rani Nisha

Department of Environmental Science and Engineering, Guru Jambheshwar

University of Science and Technology, Hisar-125 001, India

Received 16 November 2006; received in revised form 19 February 2007;

accepted 19 February 2007 Available online 23 February 2007

Pdf Abstract Biosorption of Cr(VI) using native strains of cyanobacteria from metal contaminated soil in the premises of textile mill has been reported in this paper. Biosorption was studied as a function of pH (1–5), contact time (5–180 min) and initial chromium ion concentration (5–20 mg/l) to find out the maximum biosorption capacity of alginate immobilized Nostoc calcicola HH-12 and Chroococcus sp. HH-11. The optimum conditions for Cr(VI) biosorption are almost same for the two strains (pH 3–4, contact time 30 min and initial chromium concentration of 20 mg/l) however, the biomass of Chroococcus sp. HH-11 was found to be more suitable for the development of an efficient biosorbent for the removal of Cr(VI) from wastewater, as it showed higher values of qm and Kf, the Langmuir and Freundlich isotherm parameters. Both the isotherm models were suitable for describing the biosorption of Cr(VI) by the cyanobacterial biosorbents.

 

Keywords: Algae; Heavy metal; Adsorption isotherm

 

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Cyanobacteria As A Removal Agent Of Heavy Metal

By

 

Muhammad Afdal

GS 20787

The Assignment to fulfil the subject of

Beneficial Microbe in Agrobiotechnology  

School of Graduate Study

Universiti Putra Malaysia

August 2008

 

1. Introduction

 The use of Cyanobacteria in reducing the heavy metal waste in industrial area becomes trend nowadays as it could lessen the existing of the heavy metal in the waste. This waste becomes a major cause of environment due to the health effect related with them. Many researches have been done to reduce the existing of the heavy metal from wastewater by using Cyanobacteria (Anjana et al, 2007; El-Enany and Issa, 2000; and Cain et al, 2008). Some reports mentioned that cyanobacteria have been used as an absorbent agent in removing the heavy metal like Cadmium, Lead, Cromium (Anjana et al, 2007; El-Enany and Issa, 2000; and Cain et al, 2008).  Therefore the aim of this paper is to show some information concerning the role of cyanobacteria as an agent of removing the heavy metal.

Download (Sanduak)

Blue-green Algae (pdf)

These questions and answers provide information to address health concerns about exposure to blue-green algal toxins in surface waters (lakes, rivers, streams and reservoirs).

What are blue-green algae?

Blue-green algae, technically known as cyanobacteria, are microscopic organisms that are naturally present in lakes and streams. They usually are present in low numbers. Blue-green algae can become very abundant in warm, shallow, undisturbed surface water that receives a lot of sunlight. When this occurs, they can form blooms that discolor the water or produce floating rafts or scums on the surface of the water.

 Environmental Toxicology and Pharmacology 8 (2000) 95–101

 

 

Cyanobacteria as a biosorbent of heavy metals in sewage water

A.E. El-Enany *, A.A. Issa

Botany Department, Faculty of Science, Assiut University, Assiut, Egypt Abstract (pdf)

 

The effect of sewage water on some physiological activities of cyanobacteria was studied. Metal-tolerant cyanobacterium (Nostoc linckia) and metal-sensitive (Nostoc ri6ularis) were grown at three levels of sewage water (25, 50 and 75%). The growth rate showed significant stimulation in low and moderate levels (50% for N. linckia and 25% for N. ri6ularis). Not only the number of cells was elevated but also, the time required to reach the exponential and the stationary phases was reduced. Also, low levels of sewage water increased chl.a content, photosynthetic O2-evolution, respiration and protein content. Similarly, heterocyst frequency as well as nitrogenase activity were increased in cyanobacteria grown at low and moderate levels (25 and 50% sewage). On the other hand, the high level of waste (75%) reduced growth and metabolic activities of the two species. N. linckia accumulated about 30-fold of Zn and ten-fold of Cd than those of growth medium (50% sewage water). Also, N. ri6ularis accumulated about ten-fold of Zn and two-fold of Cd. The distribution of Cd and Zn in cells were investigated. About 65–60% of Cd or Zn were found in pellets (sediment) as insoluble form in the two species. The soluble form (cytosolic fraction) after being fractionated on sephadex G-(75-100) revealed two peaks with molecular weights of 70–75 and 40–45 kDa. These peaks were in coincidence with Cd and Zn maxima. Nostoc ri6ulais showed more sensitivity to heavy metals than N. linckia, and accumulated less amount of metal-binding proteins. Nostoc linckia seems to be tolerant to heavy metals (Zn and Cd) and is able to accumulate

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