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| Titel |
Biogenic arsenic volatilisation from an acidic wetland soil |
| VerfasserIn |
Gunter Ilgen, Jen-How Huang, Shipeng Lu, Liyan Tian, Christine Alewell |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250089901
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| Publikation (Nr.) |
 EGU/EGU2014-4114.pdf |
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| Zusammenfassung |
| Biogenic arsenic (As) volatilisation was budgeted at 26000 t yr-1as the largest input of the
global As release into the atmosphere, thereby playing an important role in the
biogeochemical cycle of As in the surface environment. In order to quantify As volatilisation
from wetland soils and to elucidate the geochemical and microbiological factors governing
As volatilisation, a series of incubations with an acidic wetland soil collected in NE-Bavaria
in Germany were performed at 15oC for 4 months with addition of NaN3, arsenite (As(III)),
FeCl3, NaSO4 and NaOAc with N2 and air in the headspace. Speciation of gaseous As in
the headspace using GC-ICP-MS/ ESI-MS coupling showed the predominance of
either arsine (AsH3) or trimethylarsine ((CH3)3As) in all treatments during the
time course of incubation. Monomethylarsine ((CH3)AsH2) and dimethylarsine
((CH3)2AsH) could be only detected in trace amounts. Arsenic speciation in porewater with
HPLC-ICP-MS revealed the predominance of As(III) and methylated As was never
detectable. Arsenic volatilisation summed to 2.3 ng As (88% as AsH3) in the control
incubations, which accounted for ~0.25 % of the total As storage in the wetland soil.
Treatments with 10 mM NaN3 resulted in emission of only 0.03 ng As. In contrast,
addition of 10 mM NaOAc stimulated microbial activities in wetland soils and
subsequently rose As volatilisation to 8.5 ng As. It could be therefore concluded that
As volatilisation from the wetland soils was mainly biological. Spiking 67 μM
As(III) increased 10 times of As volatilisation and the proportion of methylated
arsines increased to 66%, which is supposed to be caused by the largely enhanced As
availability in porewater for microbes (480 ppb, ~65 times higher than those in the
controls). Adding 10 mM FeCl3 stimulated microbial Fe(III) reducing activities but
suppressed other microbial activities by lowering soil pH from 5 to 3.6, decreasing
consequently As volatilisation to 0.3 ng As. The much lower redox potential (-250 mV)
than the other incubations (-50-50 mV) caused by microbial sulphidisation may
benefit microbial As methylation. However, incubations manipulated with 10 mM
NaSO4 decreased As volatilisation to 0.8 ng As in accompany with the very low As
concentrations in porewater (~1 ppb), since sulphidisation may trap solution As by forming
AsS precipitates. In addition, the presence of O2 in headspace had no significant
influence on the amounts and speciation of As volatilisation. This study evidenced the
strong linkage between the microorganism and As volatilisation from wetland soils
and furthermore highlighted the potential utilising microbial As volatilisation to
remediate As polluted soils. Further studies will focus on investigating the correlations
between As volatilisation and microbial As methylation by quantifying the arsenite
methyltransferase (arsM) gene-containing microbial communities in treatments
mentioned above, using quantitative PCR assay with arsM-specific primer set. |
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