ISSN:0149-0451    

DOI:10.1080/01490458409377806

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Methanogenesis occurs at low rates in many marine sediments containing sulfate, in spite of an unfavorable thermodynamic and kinetic environment. One hypothesis explaining the coexistence of sulfate reduction and methanogenesis in marine sediments is that methanogens use substrates for which competition is minimal or nonexistent. Methylamines and methanol in particular have been suggested as “noncompetitive”; substrates. Data from studies of the physiology of recently isolated marine methanogens and studies using radiotracers at in situ concentrations support the notion that methylamines are important methane precursors in surface sediments. In contrast, sulfate‐reducing bacteria appear to outcompete methanogens for methanol at low concentrations (μ?), while the reverse is true at higher concentrations (e.g., > 1 mM). At present, sources of methyl‐amines are the subject of some speculation; several have been suggested, including trimethylamine oxide, choline, and glycine betaine. Of these, glycine betaine appears especially significant because of its high concentration in much of the marine biota. Studies of glycine betaine fermentation in anoxic intertidal sediments indicate that the production of stoichio‐metric amounts of acetate and trimethylamine may support both sulfate reduction and methanogenesis simultaneously. Although methanogenesis is quantitatively unimportant in carbon mineralization in most marine sediments, the use of methylamines suggests that methanogens may play an important role in the mineralization of an important class of organic nitrogen‐containing compounds.

ISSN:0149-0451    

DOI:10.1080/01490458409377807

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Some microorganisms can use reduced compounds of molybdenum as energy sources for autotrophic growth. A culture of molybdenum‐oxidizing bacteria was obtained by enrichment in a mineral‐salts medium by using samples of oxidized molybdenum ore from a molybdenum deposit as inoculum. In laboratory experiments, powellite (CaMoO4) was obtained. The role of microorganisms in the geochemistry of molybdenum is discussed.

ISSN:0149-0451    

DOI:10.1080/01490458409377808

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Addition of five types of organic matter to Lake Washington sediments resulted in release of high concentrations of iron, organic carbon, and manganese into the interstitial water, and caused an increase in observed sediment oxygen consumption rates. The depressed electrode potentials (Eh< —150 mV) that should accompany such reduction processes did not occur, indicating thatEhwas being poised by redox systems present in the sediment. Iron redox systems [Fe(OH)3‐Fe2+, Fe3(OH)8‐Fe2+, and Fe(OH)3‐Fe3(OH)8] were shown to be poising theEhof control sediments throughout 13 weeks of incubation and dominating the potential of several of the organically amended sediments following the first three weeks of incubation. Depression of calculated iron systemEovalues relative to that of the control sediment early in the incubation appeared to be due to the decreased pH and non‐equilibrium conditions in the organic matter‐amended sediment during the first weeks of incubation. Manganese redox systems exerted no discernable impact on theEhof the sediment.

ISSN:0149-0451    

DOI:10.1080/01490458409377809

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Dilute aqueous suspensions of finely divided mineral waste from phosphate ore beneficiation were allowed to consolidate in the presence of eitherAnacystis nidulansorAnabaena cylindrica.Addition to this mineral suspension of 2.2 mg (dry weight) of freshA. nidulansper milliliter of suspension resulted in solids consolidation that exceeded the untreated control by 65% after 11 days. When freshA. cylindricawas mixed with the slimes suspension, no enhancement of consolidation occurred. Addition of either 1 mgof dryA. nidulansor 1 mg of dryA. cylindricaper milliliter of suspension resulted in consolidation that exceeded the untreated control by 25% after 9 days. Direct addition of A.nidulansto the process water of facilities relying on gravitational dewatering of such mineral suspensions could reduce the residence time in the initial settling ponds. Whether such a process would affect long‐term settling is unknown.

ISSN:0149-0451    

DOI:10.1080/01490458409377810

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Microbially mediated leaching and solubilization of zinc ore concentrate by native aquatic microbial communities incubated under aerobic and oxygen‐limited conditions were examined in static microcosms consisting of stream sediment and water. Sterile controls provided information on abiotic sulfide oxidation and leaching of zinc, lead, cadmium, and copper. The flux of these heavy metals from the sediments to the water column was greatest under biotic oxygen‐limited conditions. When calculated as the percentage of total metal available in zinc concentrate‐amended microcosms, the order of metal solubilization under oxygen‐limited conditions was lead, copper, zinc, and cadmium. Under biotic aerobic conditions, the order of solubilization was zinc, lead, cadmium, and copper. This study indicates that aquatic heterotrophs are capable of leaching and solubilizing metallic sulfides under conditions of neutral to slightly acidic pH and are effective in releasing heavy metals to the water column under oxygen‐limited conditions.

ISSN:0149-0451    

DOI:10.1080/01490458409377811

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490458409377812

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490458409377813

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490458409377814

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490458409377815

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor