[en] Recent in situ ²²²Rn/²¹⁴Bi soil profile measurements on hermetically sealed and weighed samples have been made using a new, experimental field method based on sequential measurements of the prompt decay of the ²¹⁴Bi counting rate. At least two ²¹⁴Bi count rate measurements are made in the first 11/2 - 2 h after sample collection and sealing, T₀. Two subsequent ²¹⁴Bi count rate measurements are made: the first within 4 - 12 h, and the second approximately 900 h after T₀. These measurements yield the following information for each sample: (1) the extrapolated, T₀²¹⁴Bi count rate and, indirectly, the T₀ in situ ²²²Rn activity; (2) a minimum ²¹⁴Bi count rate if ²²²Rn was lost in the sampling process; and (3) a final, constant and usually a maximum ²¹⁴Bi count rate reflecting the establishment of secular radioactive equilibrium between the ²²⁶Ra, ²²²Rn and ²¹⁴Bi in the sealed sample. This information provides the basis for; (1) assessing the state of ²²⁶Ra/²²²Rn radioactive equilibrium in the soil sample for the 2-3 h period immediately preceding sample collection; (2) characterising the potential loss of ²²²Rn from a soil profile; (3) identifying factors contributing to the mobility and transport of ²²²Rn; and (4) modelling the ²²²Rn surface flux values that might be expected under different soil moisture and atmospheric conditions. (author)