Change of geographical location from Germany (Bavaria) to USA (Arizona) and its effect on H–C–N–S stable isotopes in human hair

Abstract

To receive information about the duration of a person's stay abroad related to those questions in forensics, stable isotopes of H–C–N–S were analysed in beard hair samples from four young soldiers, who went from Fürstenfeldbruck (Bavaria, Germany) to Phoenix (Arizona, USA) on the same date for their pilot training over a time period of 3 months. All study subjects were almost of the same age, had similar physical constitutions and stayed at the same military bases for the whole study period. However, the results showed considerable individual variabilities. In Arizona, hair δ¹³C increased by 2.3 ‰ (±0.6) and δ³⁴S decreased by 1.8 ‰ (±1.2). No remarkable shifts of hair δ¹⁵N and δ²H were observed. Significant shifts of δ¹³C or δ³⁴S in the shaved beard hair samples occurred 8 or 9 days after arrival in Arizona, respectively. The time lag to receive the isotope signals in hair due to US diet correspond to the growth period that hair needs to cover the distance of 2–3 mm from its root to the surface of the skin. This implies that isotopic changes due to the consumption of food and drinks were incorporated almost immediately into the hair protein. Consequently, if connected with an isotopic change of the diet, short-term stays for only a few days might be clearly recognizable within the first millimetres of a scalp hair strand which includes the hair roots.

Keywords:

• carbon-13
• food
• forensics
• geographical changes
• human hair
• hydrogen-2
• isotope forensics
• nitrogen-15
• sulphur-34

Acknowledgements

We would like to thank Michael Schwerer for establishing the contact to the soldiers of the German Air Force in Fürstenfeldbruck, and Lisa Wingenfeld for her support. We are deeply grateful to the four young soldiers for taking part as probands and sampling their beard hair material reliably over the whole study period. Furthermore, we thank Hilary Werner for language editing.

Disclosure statement

No potential conflict of interest was reported by the authors.

Funding

This study was supported by grants from the Friedrich Baur Foundation, Munich.