Spatial distributions of strontium isotope ratios in human hair and tap water from South Korea.

Natural variations of Sr/Sr ratios in biological samples, such as human hair, provide a biological record of provenance. Spatial distribution maps reflecting heterogeneity in isotopic signatures across large geographical regions are helpful for discerning the provenance and mobility of organisms. In this national-scale study conducted across South Korea, we investigated the spatial distribution patterns of Sr/Sr ratios in human hair and tap water samples to determine their spatial variabilities and the relationships of isotopic signatures between hair and tap water. The strontium isoscapes of tap water and hair showed similar spatial distribution patterns. Non-parametric comparison indicated no significant differences in isotopic ratios between the two sample types. The Sr/Sr ratios in human hair showed a significant and strong correlation with the ratios in tap water in eastern Korea, suggesting potential use of Sr/Sr ratios in provenance studies. However, tap water and hair samples from western Korea did not show significant correlation between them, overall reducing the predictive power of the hair Sr/Sr ratios for provenance studies. The deviation between Sr/Sr and Sr/Sr was much larger in western coastal areas than in eastern Korea. Relatively high utilization of groundwater or exogenous materials, such as Asian dust, may have been responsible for this pattern. To fully utilize the potential of the strontium isotope signature as a biorecorder in provenance studies, it is essential to evaluate the effects of groundwater and other exogenous materials on the isotope signatures of hair and other biological samples. In this study, only hair samples from males were used to develop Sr/Sr isoscapes. Therefore, further studies are required to examine the applicability of Sr/Sr hair isoscapes based solely on human hair samples from males to forensic and provenance studies of human hair samples from females.