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).