 |
| Titel |
Role of dust alkalinity in acid mobilization of iron |
| VerfasserIn |
A. Ito, Y. Feng |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 19 ; Nr. 10, no. 19 (2010-10-01), S.9237-9250 |
| Datensatznummer |
250008799
|
| Publikation (Nr.) |
 copernicus.org/acp-10-9237-2010.pdf |
|
|
|
|
|
| Zusammenfassung |
| Atmospheric processing of mineral aerosols by acid gases (e.g., SO2,
HNO3, N2O5, and HCl) may play a key role in the
transformation of insoluble iron (Fe in the oxidized or ferric (III) form)
to soluble forms (e.g., Fe(II), inorganic soluble species of Fe(III), and
organic complexes of iron). On the other hand, mineral dust particles have a
potential of neutralizing the acidic species due to the alkaline buffer
ability of carbonate minerals (e.g., CaCO3 and MgCO3). Here we
demonstrate the impact of dust alkalinity on the acid mobilization of iron
in a three-dimensional aerosol chemistry transport model that includes a
mineral dissolution scheme. In our model simulations, most of the alkaline
dust minerals cannot be entirely consumed by inorganic acids during the
transport across the North Pacific Ocean. As a result, the inclusion of
alkaline compounds in aqueous chemistry substantially limits the iron
dissolution during the long-range transport to the North Pacific Ocean: only
a small fraction of iron (<0.2%) dissolves from hematite in the
coarse-mode dust aerosols with 0.45% soluble iron initially. On the other
hand, a significant fraction of iron (1–2%) dissolves in the fine-mode
dust aerosols due to the acid mobilization of the iron-containing minerals
externally mixed with carbonate minerals. Consequently, the model
quantitatively reproduces higher iron solubility in smaller particles as
suggested by measurements over the Pacific Ocean. It implies that the
buffering effect of alkaline content in dust aerosols might help to explain
the inverse relationship between aerosol iron solubility and particle size.
We also demonstrate that the iron solubility is sensitive to the chemical
specification of iron-containing minerals in dust. Compared with the dust
sources, soluble iron from combustion sources contributes to a relatively
marginal effect for deposition of soluble iron over the North Pacific Ocean
during springtime. Our results suggest that more comprehensive data for
chemical specificity of iron-rich dust is needed to improve the predictive
capability for size-segregated soluble iron particles. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|