Fig. 1. Schematic representation of the ¹⁴CO₂ recovery system. Step 1 involves the addition of radiolabeled compounds to soil, incubation, and trapping any ¹⁴CO₂ evolved with a static NaOH trap. Step 2 involves the release of any additional ¹⁴CO₂ held in the soil by application of HCl and trapping evolved ¹⁴CO₂ with a series of forced-air NaOH traps. The figure is drawn to scale