Developments in Pb-210 methodologies to provide chronologies for environmental change

Abstract

Chronologies generated from core profiles to apply dates to environmental changes commonly use the measurement of the activity of radionuclides deposited and stratified with physical environmental material. The most commonly reported nuclide to define chronologies covering the last 150 years is Pb-210, for which accepted data processing methodologies in the literature have focussed on the constant rate of supply (CRS) model and the more recently published Bayesian Plum model. This short communication describes a validation approach using defined sediment layers referred to as ‘varve’ counting, which provide known points of reference to account for uncertainty between generated dates from each model using published Pb-210 measurements. A significant improvement in the chronologies was observed when applying reference date corrections to the models. This was shown to be essential in providing confidence in reported datasets and accuracy of predicted chronologies, which will better inform the interpretation of environmental change, e.g. sedimentation rates, climate change, pollution pathways and land degradation. Generated chronologies from both the CRS and Plum methods showed good agreement with the established varve dates (typically < 4-year difference).

Anthropogenic Eutrophication Drives Major Food Web Changes in Mwanza Gulf, Lake Victoria

“…Age-depth models extended back to ~ 1900 CE (± 9 years), with age estimates before this year having large uncertainties (Figure 2 ). Given the relative agreement between modeling approaches (Figure S1 ), we proceeded using the Bayesian plum model as it provides more realistic conservative estimates for deeper sediments (Aquino-López and others 2018 ; Hunter and others 2023 ). This model aligns well with the range of the most likely age-depth distribution.…”