Combination of 137Cs and 210Pb Radioactive Atmospheric Fallouts to Estimate Soil Erosion for the Same Time Scale.

Foued Gharbi,Rebai Ben Ammar,Medhat Ahmed El-Naggar,Torfa Hamad Alsheddi

doi:10.3390/ijerph17228292

Abstract

Naturally occurring 210Pb and artificial 137Cs fallouts are widely used as radioactive tracers for the determination of water-induced soil erosion for different time scales equal to 50 and 100 years, respectively. There exist several calibration models useful to convert the variation of the inventory of these radiotracers in cultivated soil compared to its value on non-disturbed soil to a soil erosion rate. The most comprehensive calibration models are based on a mass balance approach. In the present work, a new calibration model is proposed. It consists on the generalization of the mass balance approach to a cultivated soil subject to two successive and continuous periods of cultivation. The proposed model combines 210Pb and 137Cs fallouts for the same time scale by relaxing the constraint on 210Pb fallout from being used for 100 years’ time scale. The model was applied successfully to hypothetical cases and can be used to measure soil erosion rates for practical cases. It is important to note that the proposed model has two main advantages. First, the complementarity between 210Pb and 137Cs fallouts is for the same time scale and not for different time scales, as usually considered and believed in this field. Second, 210Pb fallout is used for time scales less than 100 years. This makes the model useful to estimate soil erosion rates for two successive periods of cultivation. To the best knowledge of the authors, the combination of 210Pb and 137Cs fallouts for the determination of soil erosion rate variation due to change in cultivation practices for the same time scale has never been developed or applied in the past.

Highlights

Rates of soil loss from agricultural land and associated soil degradation are important requirements for a successful environmental management
In this case,137 Cs provides the value of erosion rate during the recent period (h2 ) using the usual mass balance approach corresponding to one period of cultivation. h2 can be used to determine 210 Pbex inventory A(t1 ) at the end of the old period of cultivation by resolving the equation: h h
Equation (5) is a 210 Pbex mass balance model applied to the recent period and which uses the erosion rate h2 produced by the use of 137 Cs during a time period comparable to the time scale appropriate for the use of 137 Cs

Summary

Introduction

Rates of soil loss from agricultural land and associated soil degradation are important requirements for a successful environmental management. Rates of soil loss are strongly related to longer-term sustainability of soil resources [1]. Fallouts of 137 Cs and210 Pb are widely used to estimate rates of soil loss in the landscape [2,3,4,5,6,7,8]. 137 Cs is used to produce information on erosion rates over the past 50 years [9] and 210 Pb fallout (or 210 Pb excess, noted as 210 Pbex ) is used to provide information relating. Res. Public Health 2020, 17, 8292; doi:10.3390/ijerph17228292 www.mdpi.com/journal/ijerph

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