Calculation of flux rates
Diffusive flux rates (J ) were calculated using the following
equation, assuming stationary conditions in a first approach:
\begin{equation}
J=-\varphi\cdot D_{0}\cdot\left(1-\ln\varphi^{2}\right)^{-1}\cdot\frac{\partial C}{\partial x}\nonumber \\
\end{equation}The diffusive coefficients in free solution for seawater
(D 0)
177 cm2yr-1 and
274 cm2yr-1 for
SO42- and CH4,
respectively were calculated for 4°C in-situ temperature (Li and
Gregory, 1974; Lerman, 1979; Iversen & Jørgensen, 1993). All values
given base on the assumption of a constant porosity (\(\varphi\)) of
73 % in the deeper core sections. This value represents the average in
core GeoB22908-2(A10) as calculated by using gamma ray density
measurements (cf. Fig. S4) and assuming a matrix density of
2.65 g cm-3 (Serra, 1984).