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| Titel |
Application of synchrotron radiation for measurement of iron red-ox speciation in atmospherically processed aerosols |
| VerfasserIn |
B. J. Majestic, J. J. Schauer, M. M. Shafer |
| 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 ; 7, no. 10 ; Nr. 7, no. 10 (2007-05-14), S.2475-2487 |
| Datensatznummer |
250004981
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| Publikation (Nr.) |
 copernicus.org/acp-7-2475-2007.pdf |
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| Zusammenfassung |
| In this study, ambient atmospheric particulate matter samples were collected
using a size-resolved impactor sampler from three urban sites. The purpose
of this study is to gain a better understanding of transformations of
aerosol-bound iron as it is processed in the atmosphere. Thus, the aerosol
samples were artificially aged to represent long-term transport (10 to 40
days) or short-term transport (1 to 10 days) and were measured for iron at
several time points. At each time point, iron was measured in each size
fraction using three different techniques; 1) inductively coupled
plasma-mass spectrometry (ICPMS) for total iron, 2) x-ray absorbance near
edge structure (XANES) spectroscopy for the measurement of total Fe(II) and
Fe(III), and 3) a wet-chemical method to measure soluble Fe(II) and Fe(III).
Prior to aging, the XANES spectroscopy results show that a majority (>60%
for each size fraction) of the total iron in the PM is in the form of
Fe(III). Fe(III) was shown to be a significant fraction of the soluble iron
(sometimes >50%), but the relative significance of Fe(III) was found
to vary depending on the site. Overall, the total soluble iron depended on
the sampling site, but values ranged from less than 1% up to about 20%
of the total iron. Over the course of the 40 day aging period, we found
moderate changes in the relative Fe(II)/Fe(III) content. A slight increase
was noted in the coarse (>2.5 µm) fraction and a slight decrease in
the 0.25 to 0.5 µm fraction. The soluble fraction generally showed
(excepting one day) a decrease of soluble Fe(II) prior to 10 days of aging,
followed by a relatively constant concentration. In the short-term transport
condition, we found that the sub-micron fraction of soluble Fe(II) spikes at
1 to 3 days of aging, then decreases to near the initial value at around 6
to 10 days. Very little change in soluble Fe(II) was observed in the
super-micron fraction. |
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