Use of fallout radionuclides as indicators of erosion processes

The different depth penetration characteristics of 137Cs, 7Be and 210Pb excess in undisturbed soils can be used to identify erosion processes by analysis of sediments derived from surface erosion. Caesium-137 concentrations (half-life 30 years) typically decrease to half the surface value at between 30 and 50 mm. Beryllium-7 (half-life 53 days) has half-penetration depths of between 0.7 and 10 mm, whereas 210Pb excess (half-life 20.2 years) has half-penetration depths between 10 and 30 mm. Experiments designed to determine the applicability of these depth penetration characteristics to soil erosion studies are reported. Surface runoff was artificially generated at two locations in a grazed paddock using a rainfall simulator. Suspended sediment was extracted from runoff and analysed for natural and artificial gamma emitting radionuclides. (author)