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| Titel |
Spectrally resolved efficiencies of carbon monoxide (CO) photoproduction in the western Canadian Arctic: particles versus solutes |
| VerfasserIn |
G. Song, H. Xie, S. Bélanger, E. Leymarie, M. Babin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 6 ; Nr. 10, no. 6 (2013-06-05), S.3731-3748 |
| Datensatznummer |
250018281
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| Publikation (Nr.) |
 copernicus.org/bg-10-3731-2013.pdf |
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| Zusammenfassung |
| Spectrally resolved efficiency (i.e. apparent quantum yield, AQY) of carbon
monoxide (CO) photoproduction is a useful indicator of substrate
photoreactivity and a crucial parameter for modeling CO photoproduction
rates in the water column. Recent evidence has suggested that CO
photoproduction from particles in marine waters is significant compared to
the well-known CO production from chromophoric dissolved organic matter
(CDOM) photodegradation. Although CDOM-based CO AQY spectra have been
extensively determined, little is known of this information on the
particulate phase. Using water samples collected from the Mackenzie estuary,
shelf, and Canada Basin in the southeastern Beaufort Sea, the present study
for the first time quantified the AQY spectra of particle-based CO
photoproduction and compared them with the concomitantly determined
CDOM-based CO AQY spectra. CO AQYs of both particles and CDOM decreased with
wavelength but the spectral shape of the particulate AQY was flatter in the
visible regime. This feature resulted in a disproportionally higher visible
light-driven CO production by particles, thereby increasing the ratio of
particle- to CDOM-based CO photoproduction with depth in the euphotic zone.
In terms of depth-integrated production in the euphotic zone, CO formation
from CDOM was dominated by the ultraviolet (UV, 290–400 nm) radiation
whereas UV and visible light played roughly equal roles in CO production
from particles. Spatially, CO AQY of bulk particulate matter (i.e. the sum
of organics and inorganics) augmented from the estuary and shelf to the
basin while CO AQY of CDOM trended inversely. Water from the deep
chlorophyll maximum layer revealed higher CO AQYs than did surface water for
both particles and CDOM. CO AQY of bulk particulate matter exceeded that of
CDOM on the shelf and in the basin, but the sequence reversed in the estuary.
Without consideration of the potential role of metal oxides (e.g. iron
oxides) in particle photochemistry, mineral absorption-corrected CO AQY of
particulate organic matter (POM) could, however, surpass its CDOM
counterpart in all three sub-regions and displayed magnitudes in the estuary
that overtook those in shelf and offshore waters. In terms of CO
photoproduction, POM was thus more photoreactive than CDOM, irrespective of
the organic matter's origins (i.e. terrigenous or marine). Riverine CDOM
exhibited higher photoreactivity than marine CDOM and land-derived POM
appeared more photoreactive than marine POM. AQY-based modeling indicates
that CO photoproduction in the study area is underestimated by 12–32% if
the particulate term is ignored. |
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