I have reader that iodine was been detected in the soil south of the stricken nuclear plant in Japan. The problem is that due to radioactive decay of the iodine-131 it has not been possible for a long time to detect the iodine-131. For those who do not know it, this isotope of iodine is the isotope from a nuclear accident which tends to cause the most harm to the health of the general public.
But it is possible to make an estimate of how much iodine-131 contamination occurred to enable retrospective dosimetry to be done, the way to do it is to measure the very long lived iodine-129. In the areas of the former USSR which were strongly contaminated by the Chernobyl accident some soils samples have been examined. R. Michel et. al. in Science of the Total Environment, 2005, 340, 35-55 reported how the man made long lived iodine-129 has been used to make an estimate of the shorter lived iodine-131.