A quantitative model for estimating soil erosion rates by using 137Cs

Cesium-137 (Cs-137) has been widely used to determine soil loss rate. Many calibration relationships have been employed to estimate erosion rates from Cs-137 loss. However, there is some uncertainty since these models did not consider depth distribution pattern of Cs-137 in the soil profile and the Cs-137 fallout deposition during different times. As a result, they may over estimate or underestimate erosion rates. This paper presents a quantitative model to relate the amount of Cs-137 loss from the soil profile to the rate of soil erosion. According to the mass balance model, the depth distribution pattern of Cs-137 in the soil profile, radioactive decay of Cs-137, Sampling year and the difference in the amount of Cs-137 fallout each year were considered. Relationships between the amount of Cs-137 loss from the soil profile to the rate of soil erosion were developed by introducing an erosion constant, which is defined as the mean annual amount of relative reduction of Cs-137 and depth distribution functions of Cs-137 in the soil profile.