Then, 1 mL ofgas in the plastic tubes was sampled using a gas-tight syringe. After2 and 5 d, O2concentrations in each chamber were adjusted to theinitial concentrations after sampling of the gases. Sampled gaseswere injected into a GC system (GC-8A, Shimadzu; Kyoto, Japan) tomeasure the O2concentrations. The GC conditions were as follows:detector, thermal conductivity type; column, 5.0 m × 3.0 mm I.D.