Steady-state diagenetic model for dissolved carbonate species and pH in the pore waters of oxic and suboxic sediments

Journal Article · Wed Jul 01 04:00:00 EDT 1987 · Geochim. Cosmochim. Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(87)90187-6· OSTI ID:6996593

Boudreau, B P

An open-system diagenetic (transport) model is presented which accounts for the concurrent behavior of all the dissolved carbonate species as well as hydrogen and hydroxyl ions in the pore waters of marine sediments during the oxic and suboxic decay of organic-matter. The model includes interconversion between the dissolved carbonate species due to associationdissociation reactions as well as production by organic decay and CaCO/sub 3/ dissolution. The existence of rapid associationdissociation reactions has important consequences. First, the transport of a dissolved carbonate species is facilitated, because it can react and diffuse as another carbonate species. This action modifies the concentration profiles which would be expected without interconversion. As a consequence, the rate of CaCO/sub 3/ dissolution is increased because it is more difficult for CO/sub 3//sup =/ to reach and maintain the saturation concentration. Finally, CO/sub 2/(aq) and HCO/sub 3//sup -/ produced by decay affect the concentration of CO/sub 3//sup =/ and, therefore, the saturation state of pore waters with respect to carbonate minerals. The model is applied to the carbonate alkalinity and pH data from the Guatemala Basin and MANOP Site C. The model reproduces the sharp near-surface minimum in pH, observed at the Guatemala Basin sites; however, the carbonate alkalinity increase is underpredicted. This model result implies that there is an additional source of HCO/sub 3//sup -/ that is not presently recognized, probably in the form of sulfate reduction at depth.

• Research Organization: Univ. of British Columbia, Vancouver (Canada)
• OSTI ID: 6996593
• Journal Information: Geochim. Cosmochim. Acta; (United States), Journal Name: Geochim. Cosmochim. Acta; (United States) Vol. 51:7; ISSN GCACA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580400* -- Geochemistry-- (-1989)
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBONATE MINERALS
CARBONATES
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
DIAGENESIS
DISSOLUTION
DYNAMIC FUNCTION STUDIES
EQUILIBRIUM
GEOCHEMISTRY
GEOLOGIC MODELS
KINETICS
MINERALS
ORGANIC MATTER
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PH VALUE
REACTION KINETICS
SATURATION
SEDIMENTS
SOLUBILITY
SOLUTES
SOLVENT PROPERTIES
SOLVENTS