Strontium Isotope MC-ICP-MS Analysis of Hair Strands from Human Mummies: Transhumance Pastoralism of Early-Modern Individuals between Northern and Central Italy
Mammal hair is formed by a scleroprotein, namely
keratin, composed by some major elements (C, N, H, O, S),
but including also trace elements such as Sr, Pb, Fe, K, Na
and Ca. The latter are fixed through diet and exposure to
exogenous sources, mainly water and air. Given that the
average human scalp hair growth is ~1 cm/month, timeresolved
hair sampling yields information about a specific
period, reflecting the elemental and isotopic composition of
the diet and environment at that time. The 87Sr/86Sr ratio of
mammal tissues is generally directly correlated to the local
bioavailable strontium, providing the chance to reconstruct
the individual movements in a given time interval.
In this work, we developed our protocol to analyse low-Sr
concentration mammal hairs for their 87Sr/86Sr ratio by
Neptune MC-ICP-MS. We tested the method on a modern
individual who traveled cyclically between Italy and Brazil.
Hair strands were sampled with a time resolution of 1 to 2
months, yielding time resolved isotopic variations from the
highest radiogenic ratios of the São Paulo area to the lower
ones of Modena waters. Thus, the Sr analysis of hair has been
applied to human mummies (Roccapelago, Modena, 16th-18th
cent.). Hair strands were cut in several sub-samples with
different length (time-resolution) in relation to the amount of
available material. The best achieved time-resolution was of 3
months in a 12-cm-long strand. These samples revealed
cyclical human movements from Roccapelago to the high
radiogenic area of the Tuscan Magmatic Province. Historical
documents attest a high frequency of human seasonal travels
to Tuscany, up to the Grosseto area, likely linked to the
exploitation of transhumance pastoralism
