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| Titel |
Ash iron mobilization through physicochemical processing in volcanic eruption plumes: a numerical modeling approach |
| VerfasserIn |
G. A. Hoshyaripour, M. Hort, B. Langmann |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 16 ; Nr. 15, no. 16 (2015-08-21), S.9361-9379 |
| Datensatznummer |
250119985
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| Publikation (Nr.) |
 copernicus.org/acp-15-9361-2015.pdf |
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| Zusammenfassung |
| It has been shown that volcanic ash fertilizes the Fe-limited areas of the
surface ocean through releasing soluble iron. As ash iron is mostly insoluble
upon the eruption, it is hypothesized that heterogeneous in-plume and
in-cloud processing of the ash promote the iron solubilization. Direct
evidences concerning such processes are, however, lacking. In this study, a
1-D numerical model is developed to simulate the physicochemical interactions
of the gas–ash–aerosol in volcanic eruption plumes focusing on the iron
mobilization processes at temperatures between 600 and 0 °C. Results
show that sulfuric acid and water vapor condense at ~ 150
and ~ 50 °C on the ash surface, respectively. This liquid
phase then efficiently scavenges the surrounding gases (> 95 % of HCl,
3–20 % of SO2 and 12–62 % of HF) forming an extremely acidic
coating at the ash surface. The low pH conditions of the aqueous film promote
acid-mediated dissolution of the Fe-bearing phases present in the ash
material. We estimate that 0.1–33 % of the total iron available at the
ash surface is dissolved in the aqueous phase before the freezing point is
reached. The efficiency of dissolution is controlled by the halogen content
of the erupted gas as well as the mineralogy of the iron at ash surface:
elevated halogen concentrations and presence of Fe2+-carrying phases
lead to the highest dissolution efficiency. Findings of this study are in
agreement with the data obtained through leaching experiments. |
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