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148.
Peter Harborth Roland Fuß Kai Münnich Heinz Flessa Klaus Fricke 《Waste management (New York, N.Y.)》2013,33(10):2099-2107
Mechanical biological treatment (MBT) is an effective technique, which removes organic carbon from municipal solid waste (MSW) prior to deposition. Thereby, methane (CH4) production in the landfill is strongly mitigated. However, direct measurements of greenhouse gas emissions from full-scale MBT landfills have not been conducted so far. Thus, CH4 and nitrous oxide (N2O) emissions from a German MBT landfill in operation as well as their concentrations in the landfill gas (LFG) were measured. High N2O emissions of 20–200 g CO2 eq. m?2 h?1 magnitude (up to 428 mg N m?2 h?1) were observed within 20 m of the working face. CH4 emissions were highest at the landfill zone located at a distance of 30–40 m from the working face, where they reached about 10 g CO2 eq. m?2 h?1. The MBT material in this area has been deposited several weeks earlier. Maximum LFG concentration for N2O was 24.000 ppmv in material below the emission hotspot. At a depth of 50 cm from the landfill surface a strong negative correlation between N2O and CH4 concentrations was observed. From this and from the distribution pattern of extractable ammonium, nitrite, and nitrate it has been concluded that strong N2O production is associated with nitrification activity and the occurrence of nitrite and nitrate, which is initiated by oxygen input during waste deposition. Therefore, CH4 mitigation measures, which often employ aeration, could result in a net increase of GHG emissions due to increased N2O emissions, especially at MBT landfills. 相似文献
149.
Effect of oxygen limitation on solid-bed bioleaching of heavy metals from contaminated sediments 总被引:2,自引:0,他引:2
The effects of oxygen limitation on solid-bed bioleaching of heavy metals (Me) were studied in a laboratory percolator system using contaminated sediment supplemented with 2% elemental sulfur (So). Oxygen limitation was realized by controlling the gas flow and oxygen concentration in the aeration gas. The oxygen supply varied between 150 and 0.5 mol So (-1) over 28 d of leaching. Moderate oxygen limitation led to temporarily suppression of acidification, rate of sulfate generation and Me solubilization. Lowering the oxygen supply to 0.5 mol O2 mol So (-1) resulted in retarding acidification over a period of three weeks and in poor Me solubilization. Oxidation of So occurred even under strong oxygen limitation at a low rate. High surplus of oxygen was necessary for almost complete oxidation of the added So. The maximum Me solubilization was reached at an oxygen supply of 7.5 mol O2 mol So (-1). Thus, the oxygen input during solid-bed bioleaching can be reduced considerably by controlling the gas flow without loss of metal removal efficiency. Oxygen consumption rates, ranging from 0.4 x 10(-8) to 0.8 x 10(-8) Kg O2 Kg dm (-1) S(-1), are primarily attributed to high reactivity of the sulfur flower and high tolerance of indigenous autotrophic bacteria to low oxygen concentrations. The So related oxygen consumption was calculated assuming a molar yield coefficient Y O2/S of 1.21. The oxygen conversion degree, defined as part of oxygen feed consumed by So oxidation, increased from 0.7% to 68% when the oxygen supply was reduced from 150 to 0.5 mol O2 mol So (-1). 相似文献
150.
Bruna Plese Vladislav A. Grebenjuk Heinz C. Schröder Hans J. Breter Isabel M. Müller Werner E. G. Müller 《Marine Biology》2008,153(6):1219-1232
The cDNA sequence coding for tauropine dehydrogenase (TaDH) [belonging to the family of opine dehydrogenases] has been determined.
Using the demosponge Suberites domuncula, we describe for the first time the tauropine dehydrogenase gene (of length 2,992 kb) from a eukaryote, consisting of two
introns flanked by three exons. Moreover, two allelic variants have been identified, which are present in the different specimens
either in a homozygotic or in a heterozygotic way; the data suggest an intermediary type of heritance. Phylogenetic analyses
indicate that S. domuncula TaDH is only distantly related to the opine dehydrogenases from marine invertebrates; rather it comprises high sequence similarity
to bacterial ornithine cyclodeaminases (OCD). In addition, expression studies revealed that the steady-state level of TaDH
dropped drastically in animals, which had been exposed to elevated aeration. Antibodies raised against the recombinant sponge
TaDH were used to demonstrate that S. domuncula expresses high levels of this enzyme in almost all cells. If tissue samples were kept under additional aeration no immuno-signals
could be identified. A strong accumulation of the enzyme was seen around the bacteria, existing in bacteriocytes, indicating
that under aerobic conditions the bacteria might produce taurine. These data suggest involvement of the sponge TaDH in the final step of the glycolytic pathway, more specifically, in regeneration of NAD(+) under anaerobic conditions. Furthermore,
potential mutual influences between bacteria and sponge are discussed, claiming a horizontal gene transfer of the gene from
a bacterium to the sponge.
The following sequences from Suberites domuncula have been deposited (EMBL/GenBank): the cDNA encoding the tauropine [(carboxyethyl)-taurine/derived from sulfhydryl-amino
acids] dehydrogenase (SD_TaDH) under AM712888; the corresponding gene under AM712889; and the fragments of the sponge-associated bacteria comprising the
opine dehydrogenase domain: SUBDO_BAC1 (AM712890), SUBDO_BAC2 (AM712891), SUBDO_BAC3 (AM712892), SUBDO_BAC5 (AM712894), SUBDO_BAC6
(AM712895), SUBDO_BAC7 (AM712896), SUBDO_BAC8 (AM712897) and SUBDO_BAC9 (AM712898). 相似文献