The relationship between load and sample pressure was calibrated at 1600 °C using the following phase transformations: quartz coesite at 3.7 GPa (Kanzaki 1990); coesite stishovite at 10.26 GPa (Zhang et al. 1996); Mg2SiO4 at 15.2 GPa (Katsura et al. 2004).
In the first approach, determining the image threshold between the sample and the pressure medium is critical for accurate volume measurement (Lesher et al. 2009).
The groundwater passed through the membranes in the filter unit under differential hydraulic pressures between the sampling intervals and the pressure regulators in order to avoid abrupt changes in the hydraulic pressure in each borehole: 1.7 and 1.4 MPa in 09MI20 and 2.7 and 2.4 MPa in10MI26.
The distance between the sample and the high-pressure mercury lamp was 5.0 cm.
This step requires special care, because piston tightening should not be weak (This will allow fluid passage into the cell and changing the overall composition) and at the same time should not be too strong to avoid a pressure drop between the sample and the process line.
However, the relationship between the pressure at the sample and the pressure drop across the system is not clear for some geometries.
The use of a pressure clamp for solids was necessary to provide good contact between the sample and the diamond window used in the ATR-FTIR instrument.
Besides sulfate concentrations, the observed differences in the apparent bacterial sulfate reduction between the samples may be attributed to temperature, pressure, and the amount of reactive organic carbon in the sediment and the extent to which it can be metabolized (Boudreau & Westrich, 1984 and references therein).
This technique provides a means to ensure reproducible sample pressures between different experiments, and even between very differently designed gas-flow stages.
To avoid a flow between this silicon tube and the sample, a confining pressure, which is always 10% higher than the pressure in the percolation system, is applied, using a separate pump and a closed water cycle with distilled water.
