On the premises of mixing models to define local bioavailable 87 Sr/ 86 Sr ranges in archaeological contexts Anita Toncala a, ⁎, Bernd Trautmann a , Maren Velte a , Eva Kropf a , George McGlynn a , Joris Peters a,b , Michaela Harbeck a a SNSB, State Collection for Anthropology and Palaeoanatomy, Karolinenplatz 2a, 80333 Munich, Germany b Department of Veterinary Sciences, Institute of Paleoanatomy, Domestication Research and the History of Veterinary Medicine, Ludwig Maximilian University Munich, Kaulbachstr. 37 III, 80539 Munich, Germany HIGHLIGHTS • An improved 87 Sr/ 86 Sr mixing model for humans has been developed. • Mixing models calculated with limited sets of proxies are usually unreliable. • Mixing model analyses depend strongly on the component sampling strategy. • Caution is required when using modern samples for past mobility studies. • Kernel density analyses are helpful for determining local 87 Sr/ 86 Sr ratio ranges. GRAPHICAL ABSTRACT abstract article info Article history: Received 16 March 2020 Received in revised form 8 July 2020 Accepted 9 July 2020 Available online 17 July 2020 Editor: Jay Gan Keywords: Strontium isotopes Mixing model Kernel density estimation (KDE) Southern Germany Human mobility In archaeological mobility studies, non-local humans and animals can be identified by means of stable strontium isotope analysis. However, defining the range of local 87 Sr/ 86 Sr ratios is prerequisite. To achieve this goal, proxy- based mixing models have recently been proposed using 87 Sr/ 86 Sr ratios measured in modern local vegetation, water and soil samples. Our study complements earlier efforts by introducing archaeological animal bones as an additional proxy. We then evaluate the different modelling approaches by contrasting proxy-results gener- ated for the county of Erding (Upper Bavaria, Germany) with a comprehensive set of strontium measurements obtained from tooth enamel of late antique and early medieval human individuals (n = 49) from the same micro-region. We conclude that current mixing models based on environmental proxies clearly underestimate the locally bioavailable 87 Sr/ 86 Sr ratios due to the limited sample size of modern environmental specimens and a suit of imponderables inherent to efforts modelling complex geobiological processes. In sum, currently available mixing models are deemed inadequate and can therefore not be recommended. © 2020 Published by Elsevier B.V. 1. Introduction Human mobility and the concomitant dissemination of plants, ani- mals, material culture, technological innovations, etc. played a major role in shaping our cultural past (e.g. Metzner-Nebelsick et al., 2017). One method of choice used to address translocation in past cultures is Science of the Total Environment 745 (2020) 140902 ⁎ Corresponding author. E-mail address: toncala@snsb.de (A. Toncala). https://doi.org/10.1016/j.scitotenv.2020.140902 0048-9697/© 2020 Published by Elsevier B.V. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv