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Exercise 9
9. What is the difference between decomposition of organic matter by microflora and
digestion-assimilation in the gut of an animal? Which process is most important in
decomposition of organic matter of the whole system? Why? [See Cole (1985).J
10. What is coprophagy? How might it assist in the "processing" of particulate organic
matter?
11. Some workers believe that most of the decomposition of organic matter occurs in
the sediments rather than in the water column. What factors would enhance
benthic respiration? Enhance decomposition in the water column?
12. Some DOC and POC leave a lake in outflow. In which form would the greatest
export occur?
Apparatus and Supplies
I. Scrubbed water sampler, e.g., Van Dorn type.
2. All-glass filtration apparatus, adjustable vacuum source.
3. Glass fiber filters, e.g., Reeve Angel 984H (0.5 pm) or Whatman GF/F (0.6- to 0.7-pm pore
size), precombusted at 500°C for at least I h at temperature; forceps; micro pipets (e.g.,
Eppendorf).
4. Dissolved organic carbon:
a. I-ml ampoules; mume furnace.
b. Potassium persulfate (analytical reagent quality).
c. 3% phosphoric acid. Dilute 30ml of analytical reagent grade 85% (syrupy) H 3 P04 to
1000 ml with organic-free water. Add 10 g K 2 SZOS and heat the bottle (stopper loosened)
for 4 h in a boiling water bath. Cool and store in the same bottle; stable indefinitely.
d. Glucose standards: Dissolve 1.25 g of dry glucose in 250 ml of distilled water. Dilute 5.0 ml
of this solution to 100 ml with organic-free water. Finally, dilute 5.0 ml of the latter
solution to 100 ml with organic-free water:
I ml = I mg Cil when diluted to 5.0 ml
Prepare duplicate standards within the range of DOC anticipated, using 0.5, 1.0, 2.0, 3.0,
4.0, and 5.0 ml of the standard solution. Determinations above about 6 mg Cil may deviate
from linearity. Samples with greater concentrations of DOC can be diluted with organicfree water prior to analysis.
e. N2 and O 2 gas of high quality; ascarite CO 2 absorbant; silicone grease (e.g., Dow
Corning); flow meters; long, 20-gauge cannulae; torch for sealing ampoules; autoclave.
f. Nondispersive infrared CO2 spectrometer with recorder [a gas chromatograph can also
be used; see Stainton, et aI., (1977)J; simple gas train (as indicated in Figure 9.2);
anhydrous CaCl z .
5. Particulate organic carbon:
a. Clean 125-ml Erlenmeyer flasks, graduated IO-ml pipets, 50-ml beakers, 50-or 100-ml
stoppered graduated cylinders, centrifuge tubes.
b. Sand-bath heater or oven, 100 to 110°C.
c. Clinical centrifuge.
d. Sulfuric acid-dichromate oxidant: Dissolve 4.84 g of potassium dichromate (K 2 Cr 207) in
20 ml of distilled water. Add this solution slowly to about 500 ml of concentrated (sp. gr.
1.82) AR sulfuric acid in a 1000-ml volumetric flask. Cool to room temperature and make
to volume with more acid. Store in a glass-stoppered bottle and protect from dust. Stable
indefinitely.
e. Glucose standard solution:
i. Dissolve 7.50 g of pure glucose (dextrose) in water in a 100-ml volumetric flask and
bring up to volume with distilled water.
ii. Dilute 10.0 ml of the concentrated solution to I liter with distilled water in a volumetric
flask. Use within one day.
1.00 ml = 300 pg of carbon.
f. Spectrophotometer.
Exercise 9
9. What is the difference between decomposition of organic matter by microflora and
digestion-assimilation in the gut of an animal? Which process is most important in
decomposition of organic matter of the whole system? Why? [See Cole (1985).J
10. What is coprophagy? How might it assist in the "processing" of particulate organic
matter?
11. Some workers believe that most of the decomposition of organic matter occurs in
the sediments rather than in the water column. What factors would enhance
benthic respiration? Enhance decomposition in the water column?
12. Some DOC and POC leave a lake in outflow. In which form would the greatest
export occur?
Apparatus and Supplies
I. Scrubbed water sampler, e.g., Van Dorn type.
2. All-glass filtration apparatus, adjustable vacuum source.
3. Glass fiber filters, e.g., Reeve Angel 984H (0.5 pm) or Whatman GF/F (0.6- to 0.7-pm pore
size), precombusted at 500°C for at least I h at temperature; forceps; micro pipets (e.g.,
Eppendorf).
4. Dissolved organic carbon:
a. I-ml ampoules; mume furnace.
b. Potassium persulfate (analytical reagent quality).
c. 3% phosphoric acid. Dilute 30ml of analytical reagent grade 85% (syrupy) H 3 P04 to
1000 ml with organic-free water. Add 10 g K 2 SZOS and heat the bottle (stopper loosened)
for 4 h in a boiling water bath. Cool and store in the same bottle; stable indefinitely.
d. Glucose standards: Dissolve 1.25 g of dry glucose in 250 ml of distilled water. Dilute 5.0 ml
of this solution to 100 ml with organic-free water. Finally, dilute 5.0 ml of the latter
solution to 100 ml with organic-free water:
I ml = I mg Cil when diluted to 5.0 ml
Prepare duplicate standards within the range of DOC anticipated, using 0.5, 1.0, 2.0, 3.0,
4.0, and 5.0 ml of the standard solution. Determinations above about 6 mg Cil may deviate
from linearity. Samples with greater concentrations of DOC can be diluted with organicfree water prior to analysis.
e. N2 and O 2 gas of high quality; ascarite CO 2 absorbant; silicone grease (e.g., Dow
Corning); flow meters; long, 20-gauge cannulae; torch for sealing ampoules; autoclave.
f. Nondispersive infrared CO2 spectrometer with recorder [a gas chromatograph can also
be used; see Stainton, et aI., (1977)J; simple gas train (as indicated in Figure 9.2);
anhydrous CaCl z .
5. Particulate organic carbon:
a. Clean 125-ml Erlenmeyer flasks, graduated IO-ml pipets, 50-ml beakers, 50-or 100-ml
stoppered graduated cylinders, centrifuge tubes.
b. Sand-bath heater or oven, 100 to 110°C.
c. Clinical centrifuge.
d. Sulfuric acid-dichromate oxidant: Dissolve 4.84 g of potassium dichromate (K 2 Cr 207) in
20 ml of distilled water. Add this solution slowly to about 500 ml of concentrated (sp. gr.
1.82) AR sulfuric acid in a 1000-ml volumetric flask. Cool to room temperature and make
to volume with more acid. Store in a glass-stoppered bottle and protect from dust. Stable
indefinitely.
e. Glucose standard solution:
i. Dissolve 7.50 g of pure glucose (dextrose) in water in a 100-ml volumetric flask and
bring up to volume with distilled water.
ii. Dilute 10.0 ml of the concentrated solution to I liter with distilled water in a volumetric
flask. Use within one day.
1.00 ml = 300 pg of carbon.
f. Spectrophotometer.