FIGURE 1-SHAKE-FLASK SYSTEM FOR CARBON DIOXIDE EVOLUTION
The Ba(OH)2 container is made by placing a constriction just above the 10 mL mark of a 50 mL heavy-duty centrifuge tube and attaching the centrifuge tube to a 2 mm I.D. * 9 mm O.D. glass tube by means of 3 glass support rods. The centrifuge tube opening is large enough to permit CO2 to diffuse into the Ba(OH)2, while the constriction permits transferal of the flask to and from the shaker without Ba(OH)2 spillage into the medium. For periodic removal and addition of base from the center well, a polypropylene capillary tube, attached at one end to a 10 ml disposable syringe, is inserted through the 9 mm O.D. glass tube into the Ba(OH)2 reservoir. The reservoir access port is easily sealed during incubation with a serum bottle stopper. Two glass tubes are added for sparging, venting, and medium sampling. The tops of these tubes are connected with a short section of flexible tubing during incubation.
Table 1-Medium Employed for Assay of CO2 Evolution
Solution1 | Compound | Stock Solution Conc. (g/L) |
I | NH4Cl | 35 |
KNO3 | 15 | |
K2HPO4·3H2O | 750 | |
NaH2PO4·H2O | 25 | |
II2 | KCl | 10 |
MgSO4 | 20 | |
FeSO4·7H2O | 1 | |
III | CaCl2 | 5 |
ZnCl2 | 0.05 | |
MnCl2·4H2O | 0.5 | |
CuCl2 | 0.05 | |
CoCl2 | 0.001 | |
H3 BO3 | 0.001 | |
MoO3 | 0.0004 |
1 = Each liter of test medium contains 1 mL of each solution.
2 = Final pH is adjusted to 3.0 with 0.10 N HCl.
Percent CO2 evolution=[(TF-CF)/16.67] 100 (for 10 mg/L test compound carbon)
where:
TF = mL 0.1 N HCl required to titrate Ba(OH)2 samples from the test flask
CF = mL 0.1 N HCl required to titrate Ba(OH)2 samples from the control flask.
Percent DOC Removal=[1-(DTFx- DCFx)/(DTFo- DCFo)] 100
where:
DTF= Dissolved organic carbon from test flask
DCF= Dissolved organic carbon from control flask
o= Day zero measurements
x= Day of measurements during test.
40 C.F.R. §796.3100