250
Use of Radioisotopes to Study Biogeochemical Cycling of Elements
content is mixed. The fixed sample may be preserved for several days to be
then processed for extraction and radioassay of sulfides formed during sulfate
reduction (R;).
The processing procedure starts with filling the absorber of the apparatus
for extraction and distillation of Hlss (Fig. 5.9) with the absorbing liquid. The
mixed alkaline solution of 5% ZnS04 + Cd -acetate or 5% solutiun uf hyamine
as its mixture with 200ml methoxyethanol +800ml of toluene can be used for
this. The contents of the experimental vessel is transferred into the reaction
tube of the apparatus. Then remains of sediment are washed out from it into
the same vessel with 1 % solution of Na2C03. If the sediment is poor in carbonates, 3 ml of 5 % N a2C03 is also added. The reaction tube is attached to the
apparatus and the flow of nitrogen gas is established through the apparatus
for 2-3 min to wash out the oxygen. Then it is slowed down and via the special
to vacuum
a
b
Fig. 5.9. Scheme of apparatus for distillation of HzS from bottom sediments: a Reaction tube; b porous glass plate; c rubber bands to fix in the reaction tube; d funnel for
adding the acid; e funnel for adding the isobutanol mixture to kill the foam ; Jabsorber;
g emergency foam trap