236
Use of Radioisotopes to Study Biogeochemical Cycling of Elements
A
o
Fig. S.7A-E. Scheme of the use of 2S0-ml balloons for in situ experiments. A Washing
the balloon connected with the discharge tube of the water bottle. B Filling. C Injection of radioisotopic solution. D Measuring E h • E Experimental incubation
(or 4 % N aCl solution if the working solution of sulfide is used in seawater
samples.) The remains are washed with 0.05N NaOH. The empty space in the
balloon is blown with nitrogen via its upper end, to which then the bottle with
nitrogen gas is attached to decrease oxidation of the working solution of 30S -
sulfide thus prepared. If the batch solution appears to be already clean after
being checked, it is transferred directly into this balloon.
The following operation is to measure the approximate cpm radioactivity
to ensure that it was not lost during distillation. For this, approximately 10-20
III of this working solution from the balloon is injected into a scintillation vial
filled with cocktail and the latter is immediately radioassayed. If the radioactivity appears to be more than 510 6 cpm ml- 1 , it should be correspondingly
diluted by addition of extra deoxygenated water into the balloon. The minimal
radioactivity of the working solution should not be less than 110 6 cpmml- 1 • The
ready working solution is distributed into I-ml ampules which are filled
through the syringe needle attached to the lower end of the balloon. The liquid
in the ampules must fill the space completely up to the capillary in its neck
to leave the minimum possible air. The base of the capillary neck should be
covered with a piece of wet tape before sealing. This makes it possible to seal
the ampules closer to the surface of the liquid it contains. The absolute content
of sulfide (Ks) should be measured in one of the ampules by iodometric titration or the colorimetric method (after dilution of 0.5ml in 50ml of water).
Now the stock of Na230S working solution is ready for use for several months,
because the half-life of 35S is about 80 days.
Use of Radioisotopes to Study Biogeochemical Cycling of Elements
A
o
Fig. S.7A-E. Scheme of the use of 2S0-ml balloons for in situ experiments. A Washing
the balloon connected with the discharge tube of the water bottle. B Filling. C Injection of radioisotopic solution. D Measuring E h • E Experimental incubation
(or 4 % N aCl solution if the working solution of sulfide is used in seawater
samples.) The remains are washed with 0.05N NaOH. The empty space in the
balloon is blown with nitrogen via its upper end, to which then the bottle with
nitrogen gas is attached to decrease oxidation of the working solution of 30S -
sulfide thus prepared. If the batch solution appears to be already clean after
being checked, it is transferred directly into this balloon.
The following operation is to measure the approximate cpm radioactivity
to ensure that it was not lost during distillation. For this, approximately 10-20
III of this working solution from the balloon is injected into a scintillation vial
filled with cocktail and the latter is immediately radioassayed. If the radioactivity appears to be more than 510 6 cpm ml- 1 , it should be correspondingly
diluted by addition of extra deoxygenated water into the balloon. The minimal
radioactivity of the working solution should not be less than 110 6 cpmml- 1 • The
ready working solution is distributed into I-ml ampules which are filled
through the syringe needle attached to the lower end of the balloon. The liquid
in the ampules must fill the space completely up to the capillary in its neck
to leave the minimum possible air. The base of the capillary neck should be
covered with a piece of wet tape before sealing. This makes it possible to seal
the ampules closer to the surface of the liquid it contains. The absolute content
of sulfide (Ks) should be measured in one of the ampules by iodometric titration or the colorimetric method (after dilution of 0.5ml in 50ml of water).
Now the stock of Na230S working solution is ready for use for several months,
because the half-life of 35S is about 80 days.