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Variability of carbon monoxide and carbon dioxide apparent quantum yield spectra in three coastal estuaries of the South Atlantic Bight

Reader, Heather LU and Miller, W. L. (2012) In Biogeosciences 9(11). p.4279-4294
Abstract
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... (More)
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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Biogeosciences
volume
9
issue
11
pages
4279 - 4294
publisher
Copernicus Publications
external identifiers
  • wos:000312667300006
  • scopus:84868651407
ISSN
1726-4189
DOI
10.5194/bg-9-4279-2012
language
English
LU publication?
yes
id
075ae082-28bf-4c3a-9af8-97f1423be88d (old id 3512415)
date added to LUP
2013-02-20 15:45:57
date last changed
2017-07-30 03:08:26
@article{075ae082-28bf-4c3a-9af8-97f1423be88d,
  abstract     = {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.},
  author       = {Reader, Heather and Miller, W. L.},
  issn         = {1726-4189},
  language     = {eng},
  number       = {11},
  pages        = {4279--4294},
  publisher    = {Copernicus Publications},
  series       = {Biogeosciences},
  title        = {Variability of carbon monoxide and carbon dioxide apparent quantum yield spectra in three coastal estuaries of the South Atlantic Bight},
  url          = {http://dx.doi.org/10.5194/bg-9-4279-2012},
  volume       = {9},
  year         = {2012},
}