Dissolved inorganic carbon profiles and fluxes determined using pH and microelectrodes

Abstract

Submillimeter depth distributions of total dissolved inorganic carbon (DIC) were derived from pH and profiles measured with microelectrodes in an organic-rich, laboratory-maintained sediment. The DTC profiles were used to calculate diffusive fluxes of DIC across the sediment-water interface. In two experiments, the calculated diffusive fluxes fell within ±50% of the total flux of DIC determined by core incubation. An assessment of errors suggests that the microelectrode-derived estimates are not significantly different from measured total DIC fluxes (P = 0.05). It is concluded, therefore, that pH and microelectrode measurements can be paired to determine finescale pore-water DIC profiles and DIC diffusive fluxes. Problems will arise only in situations in which pH and gradients are extremely steep or spatially heterogeneous; this is because these conditions can cause mismatching of pH and measurements or CO2 system disequilibrium.