Figure 3

Total decay counts per minute. Typical patterns of total decay counts per minute in soil gas for ²²²Rn, ²²⁰Rn, and their daughter nuclides, ²¹⁸Po and ²¹⁶Po. Upper and lower curves represent the gases under radioactive nonequilibrium and equilibrium conditions, respectively. The solid line represents the CRAS (Koike et al. 2009) calculation, which agrees well with the measurement data denoted by circles. The upper and lower data were collected from survey points on lines FG-2 and HN-1 (Figure 1).