Caesium-137 was deposited as fallout in the 1950s and 1960s, and, in most environments, was absorbed into the soil. If this fallout was uniform, negative deviations in the distribution of caesium-137 would represent soil erosion, while positive deviations would indicate deposition. See Hardy et al. (2000) J. Hydrol. 229, 3–4.
Subjects: Earth Sciences and Geography.