Quantum yield for the photochemical production of dissolved inorganic carbon in seawater |
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| Authors: | Sophia C Johannessen William L Miller |
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| Institution: | a Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada, B3H 1P2;b Institute of Ocean Sciences, Contaminant Chemistry, 9860 W. Saanich Rd. North Saanich, B.C. Canada V8L 4B2 |
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| Abstract: | The direct photooxidation of coloured dissolved organic matter (CDOM) to dissolved inorganic carbon (DIC) may provide a significant sink for organic carbon in the ocean. To calculate the rate of this reaction on a global scale, it is essential to know its quantum yield, or photochemical efficiency. We have determined quantum yield spectra, φ(λ), (moles DIC/mole photons absorbed) for 14 samples of seawater from environments ranging from a turbid, eutrophic bay to the Gulf Stream. The spectra vary among locations, but can be represented quite well by three pooled spectra for zones defined by location and salinity: inshore φ(λ)=e−(6.66+0.0285(λ−290)); coastal φ(λ)=e−(6.36+0.0140(λ−290)); and open ocean φ(λ)=e−(5.53+0.00914(λ−290)). Production efficiency increases offshore, which suggests that the most highly absorbing and quickly faded terrestrial chromophores are not those directly responsible for DIC photoproduction. |
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| Keywords: | Marine photochemistry Carbon cycle Quantum yield Coloured dissolved organic matter Organic carbon Carbon dioxide |
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