drivers of soil respiration of root and microbial ... - Unitus DSpace

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Fig. 3 Chambers for CO2 accumulation with opened (left) and closed (right) lids.
3.2.3. Sample preparation and analyses
The CO2 from the air samples was extracted using the cryogenic line (Fig. 4) less than one
week after the collection to minimize the storage effect. Collected CO2 then could be stored for a
longer periods in the perfectly sealed test-tubes for the following analyses.
In brief, gas entering the cryogenic line passes firstly through a water trap, cooled with dry
ice ethanol mixture and then through the CO2 trap, cooled with liquid nitrogen. A pumping system
(VARIAN, TURBO-V250, FR) at the end of the line forces the gas to pass through the tubes.
Multiple loops are used to ensure that the gas molecules of CO2 and H2O are caught on their way,
The pumping system is connected to the line with a needle valve. The flow rate is measured by a
mass flow meter (Omega, UK) and regulated through the needle valve.
Fig. 4 Cryogenic line: 1-sample 2L flask with CO2, 2-mass flow meter and controller; 3-H2O trap;
4-CO2 trap; 5-pumping system; 6-dry ice ethanol mixture; 7-liquid mixture; 8-pressure gauge; 9-test tubes