Measurement of Nitrification Rate with the 14C02 Dark Uptake Method
229
8-lDmm internal diameter. They are placed into the penicillin bottles, which,
have been filled with deoxygenated natural water, containing freshly added 10
mg/100ml of Na2S9 H 20 sequenced by 0.2ml of 0.1 N HCl added to each bottle
after prefilling it with the above anoxic sulfuric water to neutralize Na2S, while
still in the laboratory before going into the field. After the addition of the
sediment into it bottle, u.2 ml ot worklOg 14C-carbonate or acetate solutIOn IS
injected into the immediately and it is closed without air bubbles air under the
stopper. The content of the bottle is mixed and it is incubated for approximately 1 day at in situ temperature if the latter is >20°C. If it is less, the incubation should be longer - up to 3 days at 3-5 dc. The exposure is ended by the
injection of 0.5ml of 3% NaOH. Then the methane thus formed is extracted
from the experimental bottles, combusted, and the 14C02 thus formed is
radioassayed using the procedure described above (see Sect. 5.2.2.). The
radioactivity of methane produced (Rm) is corrected for the control killed
with NaOH before the injection of the isotopic solution. The rate of methane
R xC x45x1D3
production (Q) is calculated as follows: Q = m
r
cm 3 dm- 3 h- 1 ,
Vxt
where Rm is the radioactivity of methane produced in the bottle during
incubation, cpm; Cr the inverse specific radioactivity of the methyl group of
labeled acetate, mg C cpm- 1 ; V the volume of sediment used in the experiment,
cm 3 ; t the incubation time, hours.
If 14C02 is taken as a label for measuring methane production, it can be
calculated with the use of the latter formula, but the inverse specific radioactivity Cr of TC02 in the experimental bottle has to be taken instead of that of
the acetate. It can be measured as described above (Sect. 2.3.2.3.).
These experiments may be performed also with intact cores of sediments.
In this case, the sediment core, taken into a corer's tube with a perforated side,
is injected with portions of isotopic solution through the holes. The remaining
procedure remains the same.
S.4 Measurement of Nitrification Rate with the 14C02 Dark
Uptake Method
This method is based on the indirect estimation of the chemosynthesis of
litho trophic nitrifying bacteria in natural samples of water and bottom sediments. Its probable rate in native populations is evaluated with the aid of the
specific nitrification inhibitor nitrapirine (N-serve), the degree of inhibition of
chemosynthetic dark 14C02 uptake in the presence of N-serve serving in this
case as the estimator of nitrification in the samples of water or sediments
(Billen 1976; Somville 1978; Saralov et al. 1983; Kuznetsov and Dubinina 1980;
Kuznetsov et al. 1985). The experiments are conducted as described above for
estimation of dark CO2 uptake rate (see Sect. 4.4.2.2). The samples of water
229
8-lDmm internal diameter. They are placed into the penicillin bottles, which,
have been filled with deoxygenated natural water, containing freshly added 10
mg/100ml of Na2S9 H 20 sequenced by 0.2ml of 0.1 N HCl added to each bottle
after prefilling it with the above anoxic sulfuric water to neutralize Na2S, while
still in the laboratory before going into the field. After the addition of the
sediment into it bottle, u.2 ml ot worklOg 14C-carbonate or acetate solutIOn IS
injected into the immediately and it is closed without air bubbles air under the
stopper. The content of the bottle is mixed and it is incubated for approximately 1 day at in situ temperature if the latter is >20°C. If it is less, the incubation should be longer - up to 3 days at 3-5 dc. The exposure is ended by the
injection of 0.5ml of 3% NaOH. Then the methane thus formed is extracted
from the experimental bottles, combusted, and the 14C02 thus formed is
radioassayed using the procedure described above (see Sect. 5.2.2.). The
radioactivity of methane produced (Rm) is corrected for the control killed
with NaOH before the injection of the isotopic solution. The rate of methane
R xC x45x1D3
production (Q) is calculated as follows: Q = m
r
cm 3 dm- 3 h- 1 ,
Vxt
where Rm is the radioactivity of methane produced in the bottle during
incubation, cpm; Cr the inverse specific radioactivity of the methyl group of
labeled acetate, mg C cpm- 1 ; V the volume of sediment used in the experiment,
cm 3 ; t the incubation time, hours.
If 14C02 is taken as a label for measuring methane production, it can be
calculated with the use of the latter formula, but the inverse specific radioactivity Cr of TC02 in the experimental bottle has to be taken instead of that of
the acetate. It can be measured as described above (Sect. 2.3.2.3.).
These experiments may be performed also with intact cores of sediments.
In this case, the sediment core, taken into a corer's tube with a perforated side,
is injected with portions of isotopic solution through the holes. The remaining
procedure remains the same.
S.4 Measurement of Nitrification Rate with the 14C02 Dark
Uptake Method
This method is based on the indirect estimation of the chemosynthesis of
litho trophic nitrifying bacteria in natural samples of water and bottom sediments. Its probable rate in native populations is evaluated with the aid of the
specific nitrification inhibitor nitrapirine (N-serve), the degree of inhibition of
chemosynthetic dark 14C02 uptake in the presence of N-serve serving in this
case as the estimator of nitrification in the samples of water or sediments
(Billen 1976; Somville 1978; Saralov et al. 1983; Kuznetsov and Dubinina 1980;
Kuznetsov et al. 1985). The experiments are conducted as described above for
estimation of dark CO2 uptake rate (see Sect. 4.4.2.2). The samples of water