Results of simultaneous monitoring of soil 222Rn and moisture at different depths in a forest site in Fukushima Prefecture, Japan

Simultaneous monitoring of soil 222Rn and soil moisture at different depths (0.3, 0.6, 1.0 m) has been conducted from May 28, 2014 to March 31, 2015 in a loamy soil under a temperate deciduous stand in Fukushima prefecture, Japan. Atmospheric precipitation higher than 0.9 mm h−1 in intensity and longer than 19 h in duration significantly reduced soil 222Rn levels at all the three soil depths. Movements of soil water and 222Rn in soil air were analyzed with sets of field data resulting in the same order of magnitude in diffusivity (0.5–7.0) × 10−6 m2 s−1 for moisture and (0.9–6.0) × 10−6 m2 s−1 for soil 222Rn. Applying “in situ” monitoring of soil 222Rn at several different soil depths could be a useful way to analyze soil water dynamics usually difficult to be evaluated.