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| Titel |
Carbon monoxide apparent quantum yields and photoproduction in the Tyne estuary |
| VerfasserIn |
A. Stubbins, C. S. Law, G. Uher, R. C. Upstill-Goddard |
| 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 ; 8, no. 3 ; Nr. 8, no. 3 (2011-03-18), S.703-713 |
| Datensatznummer |
250005572
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| Publikation (Nr.) |
 copernicus.org/bg-8-703-2011.pdf |
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| Zusammenfassung |
| Carbon monoxide (CO) apparent quantum yields (AQYs) are reported for a suite
of riverine, estuarine and sea water samples, spanning a range of coloured
dissolved organic matter (CDOM) sources, diagenetic histories, and
concentrations (absorption coefficients). CO AQYs were highest for high CDOM
riverine samples and almost an order of magnitude lower for low CDOM coastal
seawater samples. CO AQYs were between 47 and 80% lower at the mouth of
the estuary than at its head. Whereas, a conservative mixing model predicted
only 8 to 14% decreases in CO AQYs between the head and mouth of the
estuary, indicating that a highly photoreactive pool of terrestrial CDOM is
lost during estuarine transit. The CDOM absorption coefficient (a) at 412 nm
was identified as a good proxy for CO AQYs (linear regression r2 > 0.8;
n = 12) at all CO AQY wavelengths studied (285, 295, 305, 325, 345, 365, and
423 nm) and across environments (high CDOM river, low CDOM river, estuary
and coastal sea). These regressions are presented as empirical proxies
suitable for the remote sensing of CO AQYs in natural waters, including open
ocean water, and were used to estimate CO AQY spectra and CO photoproduction
in the Tyne estuary based upon annually averaged estuarine CDOM absorption
data. A minimum estimate of annual CO production was determined assuming
that only light absorbed by CDOM leads to the formation of CO and a maximum
limit was estimated assuming that all light entering the water column is
absorbed by CO producing photoreactants (i.e. that particles are also
photoreactive). In this way, annual CO photoproduction in the Tyne was
estimated to be between 0.99 and 3.57 metric tons of carbon per year, or
0.004 to 0.014% of riverine dissolved organic carbon (DOC) inputs to the
estuary. Extrapolation of CO photoproduction rates to estimate total DOC
photomineralisation indicate that less than 1% of DOC inputs are removed
via photochemical processes during transit through the Tyne estuary. |
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