Abstract
Lead (Pb) isotopes provide valuable insights into the origin of Pb within a sample, typically allowing for reliable fingerprinting of their source. This is useful for a variety of applications, from tracing sources of pollution-related Pb, to the origins of Pb in archaeological artefacts. However, current approaches investigate source proportions via graphical means, or simple mixing models. As such, an approach, which quantitatively assesses source proportions and fingerprints the signature of analysed Pb, especially for larger numbers of sources, would be valuable. Here we use an advanced Bayesian isotope mixing model for three such applications: tracing dust sources in pre-anthropogenic environmental samples, tracking changing ore exploitation during the Roman period, and identifying the source of Pb in a Roman-age mining artefact. These examples indicate this approach can understand changing Pb sources deposited during both pre-anthropogenic times, when natural cycling of Pb dominated, and the Roman period, one marked by significant anthropogenic pollution. Our archaeometric investigation indicates clear input of Pb from Romanian ores previously speculated, but not proven, to have been the Pb source. Our approach can be applied to a range of disciplines, providing a new method for robustly tracing sources of Pb observed within a variety of environments.
Highlights
Lead (Pb), a toxic, non-essential metal for life, has been an important commodity in our technological development[1] and one of the most persistent anthropogenic pollutants through time[2,3]
Model fits are developed via many Markov Chain Monte Carlo (MCMC) simulations, which produce simulations of plausible source proportions based upon the data, and probability densities
We propose an approach for applying a state-of-the-art Bayesian stable isotope mixing model (MixSIAR) to pollution sourcing and artefact tracing via Pb isotopes
Summary
Lead (Pb), a toxic, non-essential metal for life, has been an important commodity in our technological development[1] and one of the most persistent anthropogenic pollutants through time[2,3]. Other studies have been able to distinguish petrol-derived Pb41, or local ore-derived Pb from other anthropogenic sources[42], but the lack of further source consideration precludes defined provenance of such Pb to an ore body or mining region in a complex mixture[37] This is due to the limitations related to the models and the Pb isotope systems themselves, where generally only two or three isotope ratios (n) are interpreted, and limiting such models to n + 1 sources. These types of models, may be useful in a general overview, but the complexity of potential Pb inputs, in an anthropogenically polluted world, cause such approaches to be likely oversimplifications, with only limited conclusions possible[37]
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