Quantifying 137Cs uptake by suspended sediment and plant interception during transfer from rainwater to soil using an improved mass balance model

Zhang, X.C. John, Busteed, P.R., Yu, B., Yang, W.H. and Chappell, A. ORCID: https://orcid.org/0000-0002-0694-7348 2026. Quantifying 137Cs uptake by suspended sediment and plant interception during transfer from rainwater to soil using an improved mass balance model. Geoderma 472 , 117919. 10.1016/j.geoderma.2026.117919

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Abstract

Decades-long erosion monitoring in runoff plots or small watersheds is costly and labor intensive. A cost-effective alternative for estimating erosion using fallout caesium-137 (137Cs) has been explored since the 1970s. This 137Cs technique has been widely used to estimate the net (loss and gain) soil redistribution for the period from 1954 to the sampling year with a one-time field visit. However, the 137Cs technique has shortcomings in its central assumption of no 137Cs loss or redistribution during transfer from rainwater to soil. To improve the technique, we elucidate the 137Cs transfer and redistribution processes by quantifying 137Cs uptake in suspended sediment and 137Cs interception by plants during fallout. An improved 137Cs mass balance model was developed and optimized using legacy soil loss data from runoff plots along with 137Cs inventories measured during the fallout period of 1954–1976. Predicted soil loss proved highly sensitive to 137Cs redistribution by runoff and eroded sediment and interception by plants during transfer. The two processes can be effectively simulated by two key parameters: 137Cs uptake by sediment (ψ) and 137Cs interception by plants. When ψ is >1, it simulates 137Cs redistribution in runoff. When ψ is <1, it rectifies the uniform erosion assumption by accounting for rill incision from concentrated flows and can be estimated as the proportion of interrill erosion (i.e., 1 minus the rill erosion proportion). More experiments are needed to quantify ψ under different rainfall and topographic conditions to improve parameter estimation and therefore erosion prediction. The processes and estimates found in this study are broadly applicable to other radionuclides commonly used for erosion prediction.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Earth and Environmental Sciences
Publisher:	Elsevier
ISSN:	0016-7061
Date of First Compliant Deposit:	6 July 2026
Date of Acceptance:	22 June 2026
Last Modified:	02 Aug 2026 03:00
URI:	https://orca.cardiff.ac.uk/id/eprint/187923

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