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| Titel |
Quantifying atmospheric processing of mineral dust as a source of bioavailable phosphorus to the open oceans |
| VerfasserIn |
Ross Herbert, Anthony Stockdale, Ken Carslaw, Michael Krom |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250133357
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| Publikation (Nr.) |
 EGU/EGU2016-13959.pdf |
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| Zusammenfassung |
| The transport and deposition of mineral dust is known to be the dominant source of
phosphorus (P) to the surface waters of the open oceans. However, the fraction of this P that
is deemed available for primary productivity remains a key uncertainty due to a limited
understanding of the processes occurring during transport of the dust. Through a series of
detailed laboratory experiments using desert dust and dust precursors, we show that the
dissolution behaviour of P in these samples is controlled by a surface-bound labile pool, and
an additional mineral pool primarily consisting of apatite. The acid dissolution
of the apatite occurs rapidly and is controlled by the absolute number of H+ ions
present in the solution surrounding the dust. Using these results we develop a new
conceptual model that reproduces the major processes controlling P dissolution in the
atmosphere. We then use a global aerosol microphysics model with a global soil
database to quantify the deposition of bioavailable P to the open oceans and ice
sheets. We show that, globally, the labile pool contributes 2.4 Gg P a−1 to the
oceans and, from a potential pool of 11.5 Gg P a−1, the dissolved apatite pool
contributes 0.24 Gg P a−1. A series of sensitivity studies identifying sources of acid
in the atmosphere show that anthropogenic emissions of SO2 contribute 61% of
the global mass of dissolved apatite, volcanic events contribute 11%, and DMS
emissions contribute 10%. Finally, we show that the fraction of mineral dust P that
is available for primary productivity varies, regionally, from <20% in the North
Atlantic Ocean to >50% in the South Pacific Ocean; this explains the variability in
the fraction of bioavailable P commonly observed in important oceanic regions. |
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