Study of Sulfate Reduction
253
or monoliths taken with the aid of large bottom samples. The lower end of the
corer tube is tightly closed with rubber stopper. The space above the sediment
core should be covered with water.
The charging of the collected series of cores should be done within 10 h
of their sampling. To charge them, the working solution of labeled sulfate (see
above) is injected by 4U-111 portIons through the holes with the aid of a microsyringe, first by pushing the needle across the whole column and then by injecting the isotopic solution during its gradual withdrawal. The charged core is
placed for incubation as described above for the slurry method. The incubation is terminated by freezing the core. If it is impossible to do this in the field,
3-cm-Iong segments are fixed by being cut after gradually pushing the core
column up with the aid of a piston. The segments are placed into plastic containers with a mixture of 5ml of 2% ZnCl2 + 3% Na2C03' The contents of the
container is then thoroughly mixed, the container is closed, and its content
must be processed within a couple of weeks. Simultaneously, 100-cm3 samples
of sediments are taken for sol- estimation from three depths from the same
area of the bottom with the corer or from the same larger grab samples
approximately covering the vertical column of sediment taken for the experiment. These samples are packed into plastic containers, covered with a layer
of water, and closed without air bubbles under the cup. Back in the laboratory, the pore water is squeezed from these samples and their SO/- content
(Ks) is gravimetrically estimated in BaS04 precipitates collected at the
weighed membrane filters.
The processing procedure for these fixed or frozen subsamples is as
described above for the slurry method with only one difference - how the
radioactivity of labeled sulfate (Rs) is estimated. The latter is estimated in the
diluted slurry remaining after sulfide distillation. This remaining slurry is transferred into the measuring beaker, its volume is adjusted to lOOml, and its
content carefully mixed. Then 0.1-0.3-ml portions of this dilution are injected
into the scintillation vial and radio assayed in the presence of hyamine solution or BaCl2 + Zn-Cd sulfides on filter, as described above for the slurry
method. Then, having measured Ks and Rs values in the same portion of sediment taken for analysis, the specific radioactivity Sr could be calculated as
their ratio. The calculation of the rate of sulfate reduction As can be done using
the formula given above. Examples of As estimations in sediment cores are
given in Fig. 5.11.
5.6.3 Practical Implementation: Water Column
Microbial sulfate reduction and production of sulfides occur actively also in
the anoxic layers of the water column (Sorokin 1964a; Sorokin and Donato
1975). To measure their rate, samples of water are taken from the anoxic layers
of water columns into 0.3-0.5-1 bottles of the BOD type. A reason for the use
253
or monoliths taken with the aid of large bottom samples. The lower end of the
corer tube is tightly closed with rubber stopper. The space above the sediment
core should be covered with water.
The charging of the collected series of cores should be done within 10 h
of their sampling. To charge them, the working solution of labeled sulfate (see
above) is injected by 4U-111 portIons through the holes with the aid of a microsyringe, first by pushing the needle across the whole column and then by injecting the isotopic solution during its gradual withdrawal. The charged core is
placed for incubation as described above for the slurry method. The incubation is terminated by freezing the core. If it is impossible to do this in the field,
3-cm-Iong segments are fixed by being cut after gradually pushing the core
column up with the aid of a piston. The segments are placed into plastic containers with a mixture of 5ml of 2% ZnCl2 + 3% Na2C03' The contents of the
container is then thoroughly mixed, the container is closed, and its content
must be processed within a couple of weeks. Simultaneously, 100-cm3 samples
of sediments are taken for sol- estimation from three depths from the same
area of the bottom with the corer or from the same larger grab samples
approximately covering the vertical column of sediment taken for the experiment. These samples are packed into plastic containers, covered with a layer
of water, and closed without air bubbles under the cup. Back in the laboratory, the pore water is squeezed from these samples and their SO/- content
(Ks) is gravimetrically estimated in BaS04 precipitates collected at the
weighed membrane filters.
The processing procedure for these fixed or frozen subsamples is as
described above for the slurry method with only one difference - how the
radioactivity of labeled sulfate (Rs) is estimated. The latter is estimated in the
diluted slurry remaining after sulfide distillation. This remaining slurry is transferred into the measuring beaker, its volume is adjusted to lOOml, and its
content carefully mixed. Then 0.1-0.3-ml portions of this dilution are injected
into the scintillation vial and radio assayed in the presence of hyamine solution or BaCl2 + Zn-Cd sulfides on filter, as described above for the slurry
method. Then, having measured Ks and Rs values in the same portion of sediment taken for analysis, the specific radioactivity Sr could be calculated as
their ratio. The calculation of the rate of sulfate reduction As can be done using
the formula given above. Examples of As estimations in sediment cores are
given in Fig. 5.11.
5.6.3 Practical Implementation: Water Column
Microbial sulfate reduction and production of sulfides occur actively also in
the anoxic layers of the water column (Sorokin 1964a; Sorokin and Donato
1975). To measure their rate, samples of water are taken from the anoxic layers
of water columns into 0.3-0.5-1 bottles of the BOD type. A reason for the use