National-scale distribution of strontium isotope ratios in environmental samples from South Korea and its implications for provenance studies

Abstract

Successful application and accurate interpretation of strontium (Sr) isotope ratios (87Sr/86Sr) requires underlying information about the large-scale variabilities in their signatures from a variety of environmental samples, which can be correlated with the Sr isotopic signatures of underlying local geology. In this national-scale study, we analyzed 87Sr/86Sr in soil, plants, stream water, and Chinese mystery snail (Cipangopaludina chinensis) shells collected from South Korea to evaluate large-scale spatial variabilities, interpret relationships among isotopic signatures of various sample types, and generate spatial distribution isoscapes reflecting the heterogeneity of isotopic signatures across South Korea. Non-parametric comparisons among environmental samples showed non-significant differences in their isotopic ratios. The 87Sr/86Sr of plant and soil samples were strongly correlated (R2adj = 0.93), suggesting that both reflect national-scale lithological properties. Similarly, the 87Sr/86Sr of shells showed strong correlations with the 87Sr/86Sr of both plant and soil samples (R2adj = 0.90). The 87Sr/86Sr signatures of environmental samples in this study aligned with expected Sr isotopic values and generally reflected local geology. Spatial distribution maps of samples showed similar 87Sr/86Sr spatial patterns, with high radiogenic values from granitic and granitic gneiss rocks systems and low radiogenic values from volcanic and sedimentary rock systems. Stream water samples showed significant correlations with soil and plant isotopic ratios, but with a low coefficient of determination (R2adj = 0.68). The deviations were much larger for samples with 87Sr/86Sr > 0.720. Further study is needed to improve the accuracy of baseline determination and interpretation of stream water isotopic variations.