The role of alkalinity generation in controlling the fluxes of CO2 during exposure and inundation on tidal flats

[摘要] Dissolved inorganic carbon (DIC), gaseous CO₂ and alkalinity fluxesfrom intertidal sediments were investigated during periods of exposure andinundation, using laboratory core incubations, previously published fielddata and reactive transport model simulations. In the incubations andprevious field data, it was found that during periods of alkalinityproduction (attributed to the accumulation of reduced sulfur species withinthe sediment), the flux of DIC out of the sediment was greater duringinundation than the gaseous CO₂ flux during exposure by a factor of upto 1.8. This finding was supported by computational simulationswhich indicated that large amounts of sulfate reduction and reduced sulfurburial (FeS) induce an alkalinity flux from the sediment during high tideconditions. Model simulations also found that the amount of reactive Fe inthe sediment was a major driver of net alkalinity production. Our findingthat CO₂ fluxes can be significantly lower than total metabolism duringexposure has implications for how total metabolism is quantified on tidalflats.

[学科分类] 地球化学与岩石