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| Titel |
Variability of carbon monoxide and carbon dioxide apparent quantum yield spectra in three coastal estuaries of the South Atlantic Bight |
| VerfasserIn |
H. E. Reader, W. L. Miller |
| 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 ; 9, no. 11 ; Nr. 9, no. 11 (2012-11-06), S.4279-4294 |
| Datensatznummer |
250007375
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| Publikation (Nr.) |
 copernicus.org/bg-9-4279-2012.pdf |
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| Zusammenfassung |
| The photochemical oxidation of oceanic dissolved organic carbon (DOC) to
carbon monoxide (CO) and carbon dioxide (CO2) has been estimated to be
a significant process with global photoproduction transforming petagrams of
DOC to inorganic carbon annually. To further quantify the importance of
these two photoproducts in coastal DOC cycling, 38 paired apparent quantum
yield (AQY) spectra for CO and CO2 were determined at three locations
along the coast of Georgia, USA over the course of one year. The AQY spectra
for CO2 were considerably more varied than CO. CO AQY spectra exhibited
a seasonal shift in spectrally integrated (260 nm–490 nm) AQY from higher
efficiencies in the autumn to less efficient photoproduction in the summer.
While full-spectrum photoproduction rates for both products showed positive
correlation with pre-irradiation UV-B sample absorption (i.e. chromophoric
dissolved organic matter, CDOM) as expected, we found no correlation between
AQY and CDOM for either product at any site. Molecular size, approximated
with pre-irradiation spectral slope coefficients, and aromatic content,
approximated by the specific ultraviolet absorption of the pre-irradiated
samples, were also not correlated with AQY in either data set. The ratios of
CO2 to CO photoproduction determined using both an AQY model and direct
production comparisons were 23.2 ± 12.5 and 22.5 ± 9.0, respectively.
Combined, both products represent a loss of 2.9 to 3.2% of the DOC
delivered to the estuaries and inner shelf of the South Atlantic Bight
yearly, and 6.4 to 7.3% of the total annual degassing of CO2 to the
atmosphere. This result suggests that direct photochemical production of CO
and CO2 is a small, yet significant contributor to both DOC cycling and
CO2 gas exchange in this coastal system. |
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