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TZUNTIL:20121028T010000Z
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DTSTART:20101031T030000
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RDATE:20111030T030000
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DTSTAMP:20260820T034432Z
DESCRIPTION:eingeladen durch Prof Matzner. The interaction of arsenic with 
 mineral surfaces strongly influences its mobility in soil-water systems. M
 ircobial reduction of arsenate (As(V)) to arsenite (As(III)) may not only 
 increase the mobility but also the toxicity of arsenic in the environment.
  While previous studies indicated that an uptake by mineral surfaces may s
 low down microbial As(V) reduction [2]\, detailed data on this effect is s
 till lacking. Therefore\, we investigated the influence of As(V) adsorptio
 n to ferrihydrite\, goethite and boehmite on the kinetics of As(V) reducti
 on by Shewanella putrefaciens CN-32 and Shewanella ANA-3 in incubation exp
 eriments. The As(V) adsorption was changed by varying concentrations of mi
 neral suspension\, adding competitive anions (phosphate\, sulphate and exo
 polysaccahride) and the presence of microbial Fe reduction. The presence o
 f minerals apparently decreased the microbial As(V) reduction kinetics. In
 creasing amounts of ferrihydrite\, goethite or boehmite in suspension subs
 tantially decreased As(V) reduction rates. This effect increased from goet
 hite to boehmite to ferrihydrite\, in parallel with the specific surface a
 rea (600\, 250\, and 18 m2 g&#8722\;1\, respectively) and the As(V) adsorp
 tion affinity of the minerals. Both sorption competition with phosphate an
 d bacterial exopolysaccharides isolated from S. putrefaciens enhanced As(V
 ) reduction in the presence of mineral surfaces at low microbe-to-mineral 
 ratios. Both Mössbauer and X-ray absroption spectroscopy indicated the for
 mation of amorphous Fe (hydr)oxides\, e.g. ferrihydrite and magnetite\, du
 ring reductive dissolution of ferrihydrite\, leading to sequestration of a
 queous As species. In incubations with addition of electron shuttle compou
 nds such as anthraquinone-2\,6-disulfonate (AQDS)\, Fe(III) reduction may 
 at the same time inhibit microbial As(V) reduction. The data presented hig
 hlighs the important role of microorganisms in the speciation and mobility
  of As at the mineral-soultion interface.
DTSTART;TZID=Europe/Berlin:20101118T161500
DTEND;TZID=Europe/Berlin:20101118T174500
LOCATION:H6
SUMMARY:Dr. Jen-How Huang\, Inst. f. Biogeochemie u. Schadstoffdynamik\, ET
 H Zürich: Impact of microbial activity on arsenic reduction\, mobilization
  and sequestration at the mineral-solution interface
TRANSP:TRANSPARENT
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