331
9.4
Carbonate Reservoir Sizes and Fluxes Between Particulate and Dissolved Reservoirs
in 35.8 µmol cm
-2
yr
-1
at site GeoB 4906 and 33
µmol cm
-2
yr
-1
at site GeoB 4909, whereas calcite
dissolution fluxes calculated directly from Camicroprofiles are distinctively lower with 20.1 and
21.2 µmol cm
-2
yr
-1
, respectively (attributed to
scattering data and inconsistencies in the
measured profiles).
Combining these results with existing data on
calcite dissolution fluxes and C org mineralization
rates from deep-sea sediments located above the
saturation horizon and slightly below (Ω ~ 0.8;
Fig. 9.9) results in a good correlation, which has
been used to derive a general empirical formulation relating calcite dissolution and C org mineralization (Pfeifer et al. 2002):
(9.22)
where DR CaCO3 is the calcite dissolution flux and
MR Corg is the C org mineralization rate (both in µmol
cm
-2
yr
-1
).
Using Eq. 9.19, Hensen et al. (2003) calculated
an estimate of the global calcite dissolution flux
above the hydrographic lysocline by application
of a GIS-system (Fig. 9.10). To define the position
of the hydrographic lysocline, the gridded global
Fig. 9.8 Measured and simulated pore water profiles at station GeoB 4906 and corresponding rates of primary and
secondary redox processes. (b) Corresponding calcite dissolution and precipitation rates and the resulting steady-state
distribution of sedimentary CaCO 3 for input fluxes of 40, 42, and 44 g m
-2 yr
-1 , respectively, compared to measured
concentrations (bars) (after Pfeifer et al. 2002).
3
.
9
1
.
1
3
CaCO
−
⋅
=
org
C
MR
DR
Fig. 9.9 Compilation of literature-derived CaCO 3 dissolution fluxes vs. C org mineralization rates from deep-sea sediments
(after Pfeifer et al. 2002). Equation 9.22 implies that there exists a considerable threshold of mineralization, which has to
be exceeded before CaCO 3 dissolution is initiated. The increasing proportion of CaCO 3 dissolution with increasing
mineralization is indicated by the vertical and horizontal lines.
9.4
Carbonate Reservoir Sizes and Fluxes Between Particulate and Dissolved Reservoirs
in 35.8 µmol cm
-2
yr
-1
at site GeoB 4906 and 33
µmol cm
-2
yr
-1
at site GeoB 4909, whereas calcite
dissolution fluxes calculated directly from Camicroprofiles are distinctively lower with 20.1 and
21.2 µmol cm
-2
yr
-1
, respectively (attributed to
scattering data and inconsistencies in the
measured profiles).
Combining these results with existing data on
calcite dissolution fluxes and C org mineralization
rates from deep-sea sediments located above the
saturation horizon and slightly below (Ω ~ 0.8;
Fig. 9.9) results in a good correlation, which has
been used to derive a general empirical formulation relating calcite dissolution and C org mineralization (Pfeifer et al. 2002):
(9.22)
where DR CaCO3 is the calcite dissolution flux and
MR Corg is the C org mineralization rate (both in µmol
cm
-2
yr
-1
).
Using Eq. 9.19, Hensen et al. (2003) calculated
an estimate of the global calcite dissolution flux
above the hydrographic lysocline by application
of a GIS-system (Fig. 9.10). To define the position
of the hydrographic lysocline, the gridded global
Fig. 9.8 Measured and simulated pore water profiles at station GeoB 4906 and corresponding rates of primary and
secondary redox processes. (b) Corresponding calcite dissolution and precipitation rates and the resulting steady-state
distribution of sedimentary CaCO 3 for input fluxes of 40, 42, and 44 g m
-2 yr
-1 , respectively, compared to measured
concentrations (bars) (after Pfeifer et al. 2002).
3
.
9
1
.
1
3
CaCO
−
⋅
=
org
C
MR
DR
Fig. 9.9 Compilation of literature-derived CaCO 3 dissolution fluxes vs. C org mineralization rates from deep-sea sediments
(after Pfeifer et al. 2002). Equation 9.22 implies that there exists a considerable threshold of mineralization, which has to
be exceeded before CaCO 3 dissolution is initiated. The increasing proportion of CaCO 3 dissolution with increasing
mineralization is indicated by the vertical and horizontal lines.