METROL

project

methods

Distillation techniques:

Approx. 1-2 g sediment (exact weight must be known) is transferred to a flask and mixed with 10 ml 50% ethanol. The flask is attached to the distillation apparatus and connected to a distillation trap through a condenser.

The flask is flushed with N₂ for 10 min, after which 8 ml HCl (6 M) and 16 ml CrII-solution (1M) are added to liberate all reduced inorganic sulfur species (mono- and disulfides and elemental sulfur) when boiled for 40 min.

The released H₂S is trapped in 10 ml 5%-ZnAc as ZnS.

The activity of the total reduced inorganic sulfur species (TRIS) is determined by liquid scintillation counting. Half the volume of the ZnAc trap is quantitatively transferred into a counting vial and mixed with 10 ml of Lumasafe plus (Lumac BV.)

Cold distillation performed at expected sulfate reduction rate < 1 nmol SO₄^2- cm^-3 day^-1 (see also Kallmeyer et al., in press):

The sediment is resuspended in 20 ml 1,2 N-N dimethylformamide (technical grade), transferred to a flask with a magnetic stirrer and a drop of antifoam, and the flask is attached to the distillation apparatus.

The flask is flushed with N2 for 10 min, after which 8 ml HCl (6 M) and 16 ml CrII-solution (1M) are added to reduce all reduced inorganic sulfur species (mono- and disulfides and elemental sulfur). The released H₂S is trapped in 7 ml ZnAc (5 %) during 2 h of destillation.

The activity of the total reduced inorganic sulfur species (TRIS) is determined by liquid scintillation counting. The entire volume of the ZnAc trap is quantitatively transferred into a counting vial and mixed with 14 ml of Lumasafe plus (Lumac BV.)