 |
| Titel |
Dust deposition: iron source or sink? A case study |
| VerfasserIn |
Y. Ye, T. Wagener, C. Völker, C. Guieu, D. A. Wolf-Gladrow |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 8, no. 8 ; Nr. 8, no. 8 (2011-08-04), S.2107-2124 |
| Datensatznummer |
250006074
|
| Publikation (Nr.) |
 copernicus.org/bg-8-2107-2011.pdf |
|
|
|
|
|
| Zusammenfassung |
A significant decrease of dissolved iron (DFe) concentration has been
observed after dust addition into mesocosms during the DUst experiment in a
low Nutrient low chlorophyll Ecosystem (DUNE), carried out in the summer of
2008. Due to low biological productivity at the experiment site, biological
consumption of iron can not explain the magnitude of DFe decrease.
To understand processes regulating the observed DFe variation, we
simulated the experiment using a one-dimensional model of the Fe biogeochemical
cycle, coupled with a simple ecosystem model. Different size classes of
particles and particle aggregation are taken into account to describe the
particle dynamics. DFe concentration is regulated in the model by dissolution
from dust particles and adsorption onto particle surfaces, biological uptake,
and photochemical mobilisation of particulate iron.
The model reproduces the observed DFe decrease after dust addition well. This
is essentially explained by particle adsorption and particle aggregation that
produces a high export within the first 24 h. The estimated particle
adsorption rates range between the measured adsorption rates of soluble iron
and those of colloidal iron, indicating both processes controlling the DFe
removal during the experiment. A dissolution timescale of 3 days is used in
the model, instead of an instantaneous dissolution, underlining the
importance of dissolution kinetics on the short-term impact of dust
deposition on seawater DFe.
Sensitivity studies reveal that initial DFe concentration before dust
addition was crucial for the net impact of dust addition on DFe during the
DUNE experiment. Based on the balance between abiotic sinks and sources of
DFe, a critical DFe concentration has been defined, above which dust
deposition acts as a net sink of DFe, rather than a source. Taking into
account the role of excess iron binding ligands and biotic processes, the
critical DFe concentration might be applied to explain the short-term
variability of DFe after natural dust deposition in various different ocean
regions. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|