TPM, Stock of Labile Organic Matter, and its Turnover Time
291
Practically, to measure TPM, the sample, taken with a water bottle, is distributed into two BOD bottles of 2S0--300-ml capacity in the same way as the
samples for Winkler titrations, e.g., with the exit tube going down to the bottom
of the BOD bottle and passing 1-2 volumes of water during its filling. One
bottle is immediately fixed with Winkler reagents: 1 ml of each per bottle.
Another bottle is closed without air bubbles, its stopper is covered with a
plastic film fixed with a rubber band, and it is inserted in a bucket with water
in darkness. Back in the laboratory, the bottles thus collected are incubated in
complete darkness at a temperature close to that in situ. The incubation time
can be better estimated empirically with the aid of the time-course curve of
the oxygen uptake rate in series samples taken and incubated as described
above during 2-3 days. At an ambient temperature of 1S-20 °C in hypereutrophic waters, this is usually 6-8 h, in eutrophic 1S-20 h, in mesortrophic 20--30
h, in oligotrophic up to 40 h. After incubation, the oxygen in the bottles is fixed.
The Winkler titrations of these samples, both the zero time and experimental
ones, should be done very carefully and precisely, because the difference in
oxygen content between them is usually not more than 1 ml of 0.01 N thiosulfate. Therefore, both zero time and experimental samples should be processed
for Winkler titrations by a standard procedure, e.g., keeping standard time
intervals between the fixation and dissolution of precipitate, and between
dissolution and titration. From each dissolved sample two 100-ml aliquots of
iodine solution are titrated taken with a pipet fixed on a stand. Its upper end
is supplied with a three-way tap, one end of which is attached to the vacuum
source, one to the pipet, and one is open. The pipet is filled up to the tap, which
is then turned to the open end. So the content of the pipet discharges into the
titration flask. Titration should be the accomplished using a semiautomatic
pipet or automatic titration device with 0.01 N thiosulfate solution. The TPM
(K - K)x 24
values are calculated as follows: TPM =
0
I
mg02l-1 day-I, where
t
Ko and Ki are the O 2 contents in the zero time bottle and, the one incubated
during t, h. The stock of LOM in the water is estimated in the same way as the
BOD-S, but incubating the experimental bottles for 30 days at 18-20 °C in the
dark. The water samples are collected into 2-1 glass jars or polycarbonate
bottles. Back in the laboratory, the bottles are kept for some time to equalize
the temperature of the water in them at a level of 18-20 0c. Then, all of them
are saturated with oxygen by bubbling from the aquarium air compressor for
some 10min. The bottles thus bubbles are kept for half an hour to let small
bubbles come out. Then, with the aid of a syphon, three BOD bottles are filled
from each sample: one zero time and two for 30 days' experimental incubation. The remaining procedure is as with TPM estimation. From each bottle,
one 100-ml portion of iodine solution is titrated, then the stock of LOM is calculated with correction for the sue of a part of it (20%) by bacteria, for their
biosynthesis: LOM = (Ko - K;) 0.47mgCl- 1 , where Ko and Ki are the oxygen
contents in the zero-time bottle and its mean in the two experimental bottles,
mg02l-1. The turnover time (T) of the stock of LOM may be calculated as
291
Practically, to measure TPM, the sample, taken with a water bottle, is distributed into two BOD bottles of 2S0--300-ml capacity in the same way as the
samples for Winkler titrations, e.g., with the exit tube going down to the bottom
of the BOD bottle and passing 1-2 volumes of water during its filling. One
bottle is immediately fixed with Winkler reagents: 1 ml of each per bottle.
Another bottle is closed without air bubbles, its stopper is covered with a
plastic film fixed with a rubber band, and it is inserted in a bucket with water
in darkness. Back in the laboratory, the bottles thus collected are incubated in
complete darkness at a temperature close to that in situ. The incubation time
can be better estimated empirically with the aid of the time-course curve of
the oxygen uptake rate in series samples taken and incubated as described
above during 2-3 days. At an ambient temperature of 1S-20 °C in hypereutrophic waters, this is usually 6-8 h, in eutrophic 1S-20 h, in mesortrophic 20--30
h, in oligotrophic up to 40 h. After incubation, the oxygen in the bottles is fixed.
The Winkler titrations of these samples, both the zero time and experimental
ones, should be done very carefully and precisely, because the difference in
oxygen content between them is usually not more than 1 ml of 0.01 N thiosulfate. Therefore, both zero time and experimental samples should be processed
for Winkler titrations by a standard procedure, e.g., keeping standard time
intervals between the fixation and dissolution of precipitate, and between
dissolution and titration. From each dissolved sample two 100-ml aliquots of
iodine solution are titrated taken with a pipet fixed on a stand. Its upper end
is supplied with a three-way tap, one end of which is attached to the vacuum
source, one to the pipet, and one is open. The pipet is filled up to the tap, which
is then turned to the open end. So the content of the pipet discharges into the
titration flask. Titration should be the accomplished using a semiautomatic
pipet or automatic titration device with 0.01 N thiosulfate solution. The TPM
(K - K)x 24
values are calculated as follows: TPM =
0
I
mg02l-1 day-I, where
t
Ko and Ki are the O 2 contents in the zero time bottle and, the one incubated
during t, h. The stock of LOM in the water is estimated in the same way as the
BOD-S, but incubating the experimental bottles for 30 days at 18-20 °C in the
dark. The water samples are collected into 2-1 glass jars or polycarbonate
bottles. Back in the laboratory, the bottles are kept for some time to equalize
the temperature of the water in them at a level of 18-20 0c. Then, all of them
are saturated with oxygen by bubbling from the aquarium air compressor for
some 10min. The bottles thus bubbles are kept for half an hour to let small
bubbles come out. Then, with the aid of a syphon, three BOD bottles are filled
from each sample: one zero time and two for 30 days' experimental incubation. The remaining procedure is as with TPM estimation. From each bottle,
one 100-ml portion of iodine solution is titrated, then the stock of LOM is calculated with correction for the sue of a part of it (20%) by bacteria, for their
biosynthesis: LOM = (Ko - K;) 0.47mgCl- 1 , where Ko and Ki are the oxygen
contents in the zero-time bottle and its mean in the two experimental bottles,
mg02l-1. The turnover time (T) of the stock of LOM may be calculated as