Spatial patterns in ⁸⁷Sr/⁸⁶Sr ratios in modern human dental enamel and tap water from the Netherlands: Implications for forensic provenancing

The analysis of strontium isotope ratios in human dental enamel has become important in the fields of archaeological and forensic science for determining provenance and hence mobility. The prerequisite for the approach relies on a correlation between dietary Sr intake and the underlying local geology. This premise is brought into question for anthropological forensic investigations by the increasing globalisation of food supply, the establishment of nation-wide or international supermarket chains, and increasing urbanisation. To better understand the processes that cause spatial variation of Sr isotope ratios in the modern environment, this study determines the range of 87Sr/86Sr ratios in the modern Dutch environment based on 296 modern human dental enamel and tap water samples. Tap water 87Sr/86Sr from the Netherlands range from 0.70837 to 0.71278 (ΔSrmax – min = 0.0044) and modern human enamel from 0.70847 to 0.70995 (ΔSrmax – min = 0.0015). The 87Sr/86Sr ratios of tap water are predominantly determined by the underlying bedrock geology at the sampling point. In contrast, the human enamel data record an insignificant, weak correlation with water supply or local geology. Hence, the main principle behind the application of 87Sr/86Sr as a proxy for mobility appears invalid in the modern globalised Dutch context. The range of 87Sr/86Sr in modern Dutch humans that can be used for anthropological forensic investigations is between 0.7085 and 0.7100 (n = 153), with 98.0% of individuals between 0.7088 and 0.7099.