title: Modeling the downward transport of (210)Pb in Peatlands: Initial Penetration-Constant Rate of Supply (IP-CRS) model.
abstract: The vertical distribution of (210)Pb is commonly used to date peat deposits accumulated over the last 100-150 years. However, several studies have questioned this method because of an apparent post-depositional mobility of (210)Pb within some peat profiles. In this study, we introduce the Initial Penetration–Constant Rate of Supply (IP-CRS) model for calculating ages derived from 210Pb profiles that are altered by an initial migration of the radionuclide. This new, two-phased, model describes the distribution of atmospheric-derived (210)Pb ((210)Pbxs) in peat taking into account both incorporation of (210)Pb into the accumulating peat matrix as well as an initial flushing of (210)Pb through the uppermost peat layers. The validity of the IP-CRS model is tested in four anomalous (210)Pb peat records that showed some deviations from the typical exponential decay profile not explained by variations in peat accumulation rates. Unlike the most commonly used (210)Pb-dating model (Constant Rate of Supply (CRS)), the IP-CRS model estimates peat accumulation rates consistent with typical growth rates for peatlands from the same areas. Confidence in the IP-CRS chronology is also provided by the good agreement with independent chronological markers (i.e. (241)Am and (137)Cs). Our results showed that the IP-CRS can provide chronologies from peat records where (210)Pb mobility is evident, being a valuable tool for studies reconstructing past environmental changes using peat archives during the Anthropocene.
authors.affiliation: Department of Ecology and Environmental Science, Umeå University, SE-90187, Umeå, Sweden. Electronic address: olid.carolina@gmail.com.
authors.forename: Carolina
authors.initials: C
authors.lastname: Olid
authors.affiliation: Department of Earth Science, University of Bergen, NO-5020 Bergen, Norway.
authors.forename: David
authors.initials: D
authors.lastname: Diego
authors.affiliation: Departament de Física, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain; Institut de Ciència i Tecnologia Ambientals (ICTA), Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Garcia-Orellana
authors.affiliation: Departamento de Edafoloxía e Química Agrícola, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain.
authors.forename: Antonio Martínez
authors.initials: AM
authors.lastname: Cortizas
authors.affiliation: Department of Ecology and Environmental Science, Umeå University, SE-90187, Umeå, Sweden.
authors.forename: Jonatan
authors.initials: J
authors.lastname: Klaminder
keywords: (137)Cs; (210)Pb; (241)Am; Americium; Caesium; Chronology; Lead