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| Titel |
Dissolved inorganic carbon and alkalinity fluxes from coastal marine sediments: model estimates for different shelf environments and sensitivity to global change |
| VerfasserIn |
V. Krumins, M. Gehlen, S. Arndt, P. Cappellen, P. Regnier |
| 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. 1 ; Nr. 10, no. 1 (2013-01-24), S.371-398 |
| Datensatznummer |
250017478
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| Publikation (Nr.) |
 copernicus.org/bg-10-371-2013.pdf |
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| Zusammenfassung |
| We present a one-dimensional reactive transport model to
estimate benthic fluxes of dissolved inorganic carbon (DIC) and alkalinity
(AT) from coastal marine sediments. The model incorporates the
transport processes of sediment accumulation, molecular diffusion,
bioturbation and bioirrigation, while the reactions included are the redox
pathways of organic carbon oxidation, re-oxidation of reduced nitrogen, iron
and sulfur compounds, pore water acid-base equilibria, and dissolution of
particulate inorganic carbon (calcite, aragonite, and Mg-calcite). The
coastal zone is divided into four environmental units with different
particulate inorganic carbon (PIC) and particulate organic carbon (POC)
fluxes: reefs, banks and bays, carbonate shelves and non-carbonate shelves.
Model results are analyzed separately for each environment and then scaled
up to the whole coastal ocean. The model-derived estimate for the
present-day global coastal benthic DIC efflux is 126 Tmol yr−1, based on
a global coastal reactive POC depositional flux of 117 Tmol yr−1. The
POC decomposition leads to a carbonate dissolution from shallow marine
sediments of 7 Tmol yr−1 (on the order of 0.1 Pg C yr−1. Assuming
complete re-oxidation of aqueous sulfide released from sediments, the
effective net flux of alkalinity to the water column is 29 Teq. yr−1,
primarily from PIC dissolution (46%) and ammonification (33%).
Because our POC depositional flux falls in the high range of global values
given in the literature, the reported DIC and alkalinity fluxes should be
viewed as upper-bound estimates. Increasing coastal seawater DIC to what
might be expected in year 2100 due to the uptake of anthropogenic CO2
increases PIC dissolution by 2.3 Tmol yr−1and alkalinity efflux by
4.8 Teq. yr−1. Our reactive transport modeling approach not only yields
global estimates of benthic DIC, alkalinity and nutrient fluxes under
variable scenarios of ocean productivity and chemistry, but also provides
insights into the underlying processes. |
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