Effects of added manganic and ferric oxides on sulfate reduction and sulfide oxidation in intertidal sediments

Abstract Freshly precipitated iron or manganese oxides were added to surface sediments from a salt marsh and from the intertidal region of Lowes Cove, Maine. In the presence of added manganese, sulfate was formed under anoxic conditions, suggesting a manganese dependent sulfide oxidation. Sulfate formation was not observed with iron additions. Sulfate reduction was substantially but not completely inhibited by either metal oxide, even though both were added at levels well in excess though both were added at levels well in excess of natural concentrations. Manganese-catalysed sulfide oxidation was further documented using a combination of radiolabel, metal oxide, and inhibitor additions, Results from this study suggested that losses of radiolabelled sulfide could result in underestimates of gross sulfate reduction rates in the presence of significant manganic oxide concentrations. In addition, manganic oxides may facilitate the anaerobic regeneration of sulfate from sulfides.     

Role of menaquinone in the reduction of fumarate, nitrate, iron(III) and manganese(IV) by Shewanella putrefaciens MR-1

Abstract Mutants of Shewanella putrefaciens MR-1 deficient in menaquinone and methylmenaquinone, but which have wild-type levels of ubiquinone, retain the ability to use trimethylamine N -oxide as an electron acceptor, but they lose the ability to use nitrate, iron(III), and fumarate as electron acceptors. These mutants also show a reduced rate of manganese(IV) reduction. One of these mutants could be restored to essentially wild-type phenotype by supplementing the medium with 1,4-dihydroxy-2-naphthoic acid. A requirement for naphthoquinones in iron(III) reduction and a preference for naphthoquinones in manganese(IV) reduction provide further support that the metal reducing systems in MR-1 are linked to anaerobic respiration.     

Start-up procedures and analysis of heavy metals inhibition on methanogenic activity in EGSB reactor

The effectiveness of operating an industrial UASB reactor, treating wastewater from the beer industry, with flows containing heavy metals was evaluated. A pilot-scale UASB reactor, already used to simulate the industrial reactor, was unsuccessfully employed. An easy start-up was obtained arranging it as an EGSB reactor. Considerations about this modification are reported. The effects of Cu(II), Ni(II) and Cr(III) ions on the anaerobic activity were analyzed by measurements of methane production rate and COD removal. The employed biomass was the sludge of the industrial UASB reactor, while a solution of ethanol and sodium acetate with COD of 3000 mg/L and a heavy metal concentration of 50 mg/L were continuously fed. Experimental results proved higher biomass sensitivity for copper and much slighter for nickel and chromium. Moreover, copper inhibition has been demonstrated to be less significant if a metal-free feed was provided to the system before copper addition.     

Incidence of heavy metals in the mangrove flora and sediments in Kerala, India

The mangroves of Kerala on the south-west coast of India are fast disappearing due to land reclamation and other anthropogenic disturbances. There are very few ecosystem level studies made in these much threatened biotopes in Kerala. The present study involves the measurement of heavy metals in the mangrove flora and sediments of three mangrove habitats along the Kerala coast. Sampling was carried out for a period of one year at bi-monthly intervals, with concentrations of Fe, Mn, Cu,Zn,Pb and Co analysed using atomic absorption spectrophotometry. An appreciable variation was observed in metal concentrations indifferent mangrove species. Cu, Zn and Pb were found to be in higher concentrations in Avicennia officinalis whereas higher levels of Fe, Mn and Co were observed in the species Barringtonia racemosa. The analysis of heavy metals indicated a high level of metal pollutants such as Fe, Cu, Zn and Pb in the mangrove habitats of Quilon and Veli compared to the relatively uncontaminated areas of Kumarakom. This revised version was published online in August 2006 with corrections to the Cover Date.     

Anaerobic respiration of Shewanella putrefaciens requires both chromosomal and plasmid-borne genes

Abstract Pleiotropic respiratory mutants, incapable of growth on any electron acceptor other than oxygen, were isolated from two strains of Shewanella putrefaciens (MR-1 and sp200). All anaerobic respiratory functions were restored by complementation of the mutants with specific cloned DNA fragments. Southern hybridization experiments revealed that the fragment that complements the MR-1 mutant was localized on the megaplasmids of both strains, while the fragment that complements the sp200 mutant was chromosomal. Neither of these fragments hybridized with the anaerobic regulatory genes of S. putrefaciens ( etrA ) or E. coli ( fnr ).     

Assessment of Heavy Metal Mobility in Dredged Sediments: Porewater Analysis,Single and Sequential Extractions

Dredged sediments from the Leie catchment (Belgium) that were deposited on land between 70 and 10 years ago were characterized according to their physico-chemical properties, total metal concentrations and porewater composition. Actual and potential heavy metal availability was assessed by means of single extractions with 0.01 M CaCl ₂ , 0.05 M EDTA and 0.43 M acetic acid. A modified version of the BCR (Community Bureau of Reference) extraction procedure, adapted to the elevated acid neutralizing capacity of the sediments, was applied. Information on element mobility was assessed and the used methodologies were critically evaluated.

The favorable physico-chemical characteristics of dredged sediments from the catchment of the Leie River (N-Belgium) indicated a rather low actual heavy metal mobility. Based on CaCl ₂ and EDTA extractions, the distribution of Cd, Zn and Ni between the solution and sorbed phase could be described as a function of pH and organic carbon content. Cd and Zn were found to be the elements with the highest potential availability, while Cu and Ni displayed a medium availability. It is stressed that different types of extractions deal with heavy metal mobility in a different way and that the measurement of “key-factors” such as the pH of the extracts can be helpful for the interpretation of the results.     

Accumulation and distribution of iron, cadmium, lead and nickel in cucumber plants grown in hydroponics containing two different chelated iron supplies

Cucumber plants grown in hydroponics containing 10 μM Cd(II), Ni(II) and Pb(II), and iron supplied as Fe(III) EDTA or Fe(III) citrate in identical concentrations, were investigated by total-reflection X-ray fluorescence spectrometry with special emphasis on the determination of iron accumulation and distribution within the different plant compartments (root, stem, cotyledon and leaves). The extent of Cd, Ni and Pb accumulation and distribution were also determined. Generally, iron and heavy-metal contaminant accumulation was higher when Fe(III) citrate was used. The accumulation of nickel and lead was higher by about 20% and 100%, respectively, if the iron supply was Fe(III) citrate. The accumulation of Cd was similar. In the case of Fe(III) citrate, the total amounts of Fe taken up were similar in the control and heavy-metal-treated plants (27-31 μmol/plant). Further, the amounts of iron transported from the root towards the shoot of the control, lead- and nickel-contaminated plants were independent of the iron(III) form. Although Fe mobility could be characterized as being low, its distribution within the shoot was not significantly affected by the heavy metals investigated.     

Members of the genus Arthrobacter grow anaerobically using nitrate ammonification and fermentative processes: anaerobic adaptation of aerobic bacteria abundant in soil

Members of the genus Arthrobacter are usually regarded as obligate aerobic bacteria. The anaerobic growth and energy metabolism of two Arthrobacter species were investigated. Arthrobacter globiformis utilized both nitrate ammonification and lactate, acetate and ethanol producing fermentation processes for anaerobic growth. Only nitrate supported anaerobic growth of Arthrobacter nicotianae. Anaerobically induced respiratory nitrate reductase activity was detected in both strains. Neither of the tested strains used the alternative electron acceptors fumarate, dimethylsulfoxide or trimethylamine-N-oxide.     

Anaerobic co-metabolic oxidation of 4-alkylphenols with medium-length or long alkyl chains by <Emphasis Type="Italic">Thauera</Emphasis> sp., strain R5

A 4-alkylphenol-degrading facultative anaerobic bacterium, strain R5, was isolated from paddy soil after enrichment with 4-n-propylphenol, 4-n-butylphenol and 4-hydroxybenzoate (4-HBA) under nitrate-reducing conditions. Strain R5 is a Gram-negative rod bacillus grown on phenolic compounds with short alkyl chains (≤C2), organic acids and ethanol. The sequence of the 16S ribosomal RNA gene revealed that the strain is affiliated with Thauera sp. In the presence of 4-HBA as a carbon source, the strain transformed 4-n-alkylphenols with a medium or long-length alkyl chain (C3–C8) to the corresponding oxidised products as follows: 1-(4-hydroxyphenyl)-1-alkenes, -(4-hydroxyphenyl)-1-alkanones and/or 1-(4-hydroxyphenyl)-1-alcohols. The strain also transformed 4-i-propylphenol and 4-sec-butylphenol to (4-hydroxyphenyl)-i-propene and (4-hydroxyphenyl)-sec-butene but not 4-alkylphenols with tertiary alkyl chains (4-t-butylphenol or 4-t-octylphenol). The biotransformation did not proceed without another carbon source and was coupled with nitrate reduction. Biotransformation activity was high in the presence of p-cresol, 4-ethylphenol, 4′-hydroxyacetophenone and 4-HBA as carbon sources and low in the presence of organic acids and ethanol. We suggest that strain R5 co-metabolically transforms alkylphenols to the corresponding metabolites with oxidised alpha carbon in the alkyl chain during coupling with nitrate reduction.     

Influence of soil waterlogging on subsequent plant growth and trace metal content

Summary The uptake of trace metals by two plant species (French bean and maize) has been measured on two soils subjected to various waterlogging regimes. Uptake of both manganese and iron was increased due to soil waterlogging, although reoxidation of the soil affected iron more than manganese. Zinc and copper uptake was influenced by a species factor; French bean (Phaseolus vulgaris) showed preferential uptake of zinc, whereas maize (Zea mays) took up copper preferentially. Uptake of cobalt by both species was increased due to waterlogging, following the pattern of manganese.The abilities of these species to take up trace metals from soil followed the pattern predicted by selective extraction of soil for manganese, iron and cobalt, but not for zinc and copper.     

Sources and Contamination of Heavy Metals in Sediments of Kabul River: The Role of Organic Matter in Metals Retention and Accumulation

In this study, sediment samples were collected from Kabul River (Pakistan) and analyzed for heavy metals including zinc (Zn), cadmium (Cd), chromium (Cr), nickel (Ni) and lead (Pb). The physico-chemical characteristics were also determined which are known to influence the metal accumulation within the sediment matrix. Heavy metal concentrations (mg kg^?1, dry weight basis) in the sediment were in the order of Zn > Cr > Ni > Pb > Cd. Heavy metal concentrations were found in moderately polluted category set by U. S. Environmental Protection Agency (USEPA). However, Cr and Ni concentrations exceeded the screening levels at the sites where a larger volume of industrial effluents enter into Kabul River. Higher concentrations of almost all the tested metals were detected at locations of greater industrial and sewage entry points. Sediment organic matter (OM) exhibited strong correlation with Pb (R² = 0.80), Ni (R² = 0.67) and Zn (R² = 0.46), indicating that OM plays a significant role in metal retention and accumulation. The findings of this study showed that Kabul River is reasonably contaminated with selected heavy metals released from anthropogenic sources. In the study area, sewage discharge was the major source of heavy metals including Zn and Pb, which were observed at locations where sewage effluents enter into the river.     

Sorption and desorption of trace elements bySpartina alterniflora detritus

Element and extractant-specific desorption of Mn, Fe, Cu, and Zn fromSpartina alterniflora detritus was observed. Desorption of a substantial fraction of the total detrital Mn, Fe, Cu and Zn occured rapidly when the detritus was treated with 0.1N HCl or 1 MgCl₂. This treatment removed precipitated/coprecipitated and adsorbed trace elements, respectively, suggesting that a large fraction of detritus-bound trace elements are in readily exchangeable, surface reaction sites. The carboxylic acid functional group cation exchange capacity of the detritus also suggests an important role of surface exchange reactions in the dynamics of trace elements during decomposition. The rate and magnitude of changes in the trace element content of detritus has important implications for estuarine biogeochemical cycling of these elements including the potential for biological uptake of trace elements by detritus-consuming fauna.This research was supported by a cooperative agreement between the National Marine Fisheries Service and the US Department of Energy. The opinions or assertions contained herein are the private views of the authors and are not to be construed or reflecting the views of the Department of the Army or the Department of Defense. Special thanks to Dr. W. L. Johnson who provided the proximate analyses, Southeast Fisheries Center Contribution No. 82-10B.