This study introduces a new zircon reference material, LKZ-1, for the in situ U–Pb dating and O–Hf isotopic and trace element analyses. The secondary ion mass spectrometric analyses for this gem-quality single-crystal zircon yielded a weighted mean ²⁰⁶Pb/²³⁸U age of 572.6 ± 2.0 Ma (2σ, n = 22, MSWD = 0.90), with moderately high U concentrations (619 ± 21 ppm, 1 SD), restricted Th/U ratios (0.146 ± 0.002, 1 SD), and negligible common Pb content (²⁰⁶Pb_c < 0.2%). A comparable ²⁰⁶Pb/²³⁸U age (570.0 ± 2.5 Ma, 2σ) was produced by the isotope dilution-thermal ionization mass spectrometry. The secondary ion mass spectrometric and laser ablation-assisted multiple collector inductively coupled plasma mass spectrometer analyses respectively showed that LKZ-1 had little variation in O (δ¹⁸O_V-SMOW = 10.65 ± 0.14‰; laser fluorination value = 10.72 ± 0.02‰; 1 SD) and Hf (¹⁷⁶Hf/¹⁷⁷Hf = 0.281794 ± 0.000016, 1 SD) isotopic compositions. LKZ-1 was also fairly homogeneous in its chemical composition (RSD of laser ablation ICPMS data ≤ 10%), displaying a relatively uniform chondrite-normalized rare earth element pattern ((Lu/Gd)_N = 31 ± 3, Eu/Eu^* = 0.43 ± 0.17, Ce/Ce^* = 44 ± 32; 1 SD). These consistencies suggest that the LKZ-1 zircon is a suitable working standard for geochronological and geochemical analyses.

Thermal ionization mass spectrometry (TIMS) can provide highly accurate strontium (Sr), neodymium (Nd), and lead (Pb) isotope measurements for geological and environmental samples. Traces of these isotopes are useful for understanding crustal reworking and growth. In this study, we conducted a sequential separation of Sr, Nd, and Pb and subsequently measured the ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd, ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb ratios of 13 widely used rock certified reference materials (CRMs), namely BCR-2, BHVO-2, GSP-2, JG-1a, HISS-1, JLk-1, JSd-1, JSd-2, JSd-3, LKSD-1, MAG-1, SGR-1, and 4353A, using TIMS. In particular, we reported the first isotopic ratios of Sr, Nd, and Pb in 4353A, Sr and Nd in HISS-1 and SGR-1, and Sr in JLk-1, JSd-2, JSd-3, and LKSD-1. The Sr–Nd–Pb isotopic compositions of most in-house CRMs were indistinguishable from previously reported values, although the Sr and Pb isotopic ratios of GSP-2, JSd-2, JSd-3, and LKSD-1 obtained in different aliquots and/or batches varied slightly. Hence, these rock reference materials can be used for monitoring the sample accuracy and assessing the quality of Sr–Nd–Pb isotope analyses.

Stable H-O and radiogenic Sr isotopic compositions of bottled water in South Korea were investigated to trace water origins and to elucidate hydrogeochemical water-rock interactions within aquifers. Eighty-one bottled water samples were collected across the country. The δD and δ¹⁸O values, and ⁸⁷Sr/⁸⁶Sr ratios and Sr contents of groundwater-sourced bottled water samples were in the ranges of -68 to -40 ‰, -10 to -7 ‰, 0.7050-0.8112, and 14-400 μg L^-1, respectively. The corresponding ranges for desalinated deep-ocean water samples were -1.2 to 1.6 ‰, -0.35 to 0.10 ‰, 0.7078-0.7092, and 12-407 μg L^-1, respectively. Isotopic compositions indicate spatial variations in stable isotopic signatures with geographical location, while Sr isotopic ratios are correlated with the geological characteristics of water sources. Oxygen isotopic compositions of bottled water show a negative correlation with latitude, while Sr isotopic ratios vary with aquifer geology. The integration of stable and radiogenic isotopic compositions improves our understanding of water-rock interactions, enabling accurate authentication of water sources.

In this study, we introduce the stable isotopic results of water using a recently installed high sensitivity isotope ratio mass spectrometry (HS-IRMS) system at the Korea Institute of Geoscience and Mineral Resources (KIGAM). As a result of analytical method validation through an international proficiency test, the 2020 WICO (Water Isotope Inter-Comparison), organized by the International Atomic Energy Agency, the KIGAM IRMS laboratory showed satisfactory performance. Furthermore, stable isotopic compositions of bottled water samples from South Korea were measured using the HS-IRMS with a high temperature conversion elemental analyzer, and this method was re-validated and confirmed by a comparison with stable isotope results obtained using an equilibrium method.