HR: 0800h
AN: OS11B-0509    [Abstracts]
TI: Volcanic ash as an iron-fertilizer in ocean surface water
AU: * Olgun, N
EM: nolgun@ifm-geomar.de
AF: Leibniz-Institute of Marine Sciences, IFM-GEOMAR, Division Dynamics of the Ocean Floor, Wischhofstr. 1-3, Kiel, 24148, Germany
AU: * Olgun, N
EM: nolgun@ifm-geomar.de
AF: Leibniz-Institute of Marine Sciences, IFM-GEOMAR, Division Marine Biogeochemistry, Duesternbrooker Weg 20, Kiel, 24105, Germany
AU: Duggen, S
EM: sduggen@ifm-geomar.de
AF: Leibniz-Institute of Marine Sciences, IFM-GEOMAR, Division Dynamics of the Ocean Floor, Wischhofstr. 1-3, Kiel, 24148, Germany
AU: Croot, P
EM: pcroot@ifm-geomar.de
AF: Leibniz-Institute of Marine Sciences, IFM-GEOMAR, Division Marine Biogeochemistry, Duesternbrooker Weg 20, Kiel, 24105, Germany
AU: Dietze, H
EM: hdietze@ifm-geomar.de
AF: Leibniz-Institute of Marine Sciences, IFM-GEOMAR, Division Marine Biogeochemistry, Duesternbrooker Weg 20, Kiel, 24105, Germany
AU: Schacht, U
EM: uschacht@co2crc.com.au
AF: Australian School of Petroleum, Univ. of Adelaide, Adelaide, SA 5005, Australia
AU: Oskarsson, N
EM: nielso@hi.is
AF: Inst. of Earth Sciences, Univ. of Iceland, Reykjavic, 101, Iceland
AU: Siebe, C
EM: csiebe@tonatiuh.igeofcu.unam.mx
AF: Instituto de Geofisica, UNAM, Mexico, 04510, Mexico
AU: Auer, A
EM: aui-post@web.de
AF: Univ. of Wuerzburg, Pleicherwall 1, Wuerzburg, 97070, Germany
AB: Surface ocean fertilisation with iron may affect the marine primary productivity, C-cycles and eventually climate development. Volcanic ash has the potential to release iron on contact with seawater and to stimulate phytoplankton growth (1,2) but the relative importance of volcanism at destructive plate margins (subduction zones, SZ) and intraplate volcanic settings (ocean islands at hot spots) remains unknown. Here we present new results from geochemical experiments with natural seawater and numerous volcanic ash samples from SZ volcanoes in the Pacific Ring of Fire (Alaska, Japan, Kamchatka, Northern and Central America and Papua New Guinea) and hot spot volcanoes (on Iceland and Hawaii). The release of iron as a function of time was determined in situ in seawater by means of Cathodic Stripping Voltammetry. Our experiments show that: A) volcanic ash from both SZ and hot spot volcanic areas mobilise significant amounts of iron, B) with the highest mobilisation rates within the first 10-20 minutes and C) indicate that volcanic ash from hot spot volcanoes mobilise less iron than volcanic ash from SZ. We propose that the higher iron-mobilisation potential of SZ volcanic ash results from higher HCl/HF ratios in SZ volcanic gases that seem to be involved in the formation of Fe-bearing soluble salt coatings (condensed gases and adsorbed aerosols) on ash particles (1,2,3). Higher HCl/HF ratios in SZ volcanic gases thus appear to be linked to the recycling of seawater through subduction of oceanic lithosphere at destructive plate margins. Together, taking into account differences in ash-fluxes from SZ and hot spot volcanoes into the oceans, our study suggests that SZ volcanic ash plays a more important role for the global surface ocean iron budget than ash from volcanoes in hot spot areas. 1 Frogner, Gislason, Oskarsson (2001). Geology, 29, 487-490. 2 Duggen, Croot, Schacht, Hofmann (2007) Geoph. Res. Letters 34, 5. 3 Oskarsson (1980), J. Volc. and Geoth. Res. 8, 251-266.
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 4845 Nutrients and nutrient cycling (0470, 1050)
DE: 8408 Volcano/climate interactions (1605, 3309)
DE: 8430 Volcanic gases
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting