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Lithium has two naturally occurring isotopes, 6 Li and 7 Li, with approximate relative abundances of 7.5% and 92.5%, respectively. Due to large Li isotope variations in nature, lithium isotopes have the potential to reveal important information relevant to nuclear technology, biomedicine, astrophysics, and geochemistry. With the advent of multi-collector inductively coupled mass spectrometry (MC-ICP-MS), studies of Li isotopes have largely focused on the analysis of geological materials, with varying degrees of accuracy. However, this technique has often been affected by either baseline interferences or isobaric interferences on mass 6 and 7 during ionization in Ar plasma, which is mainly due to the Li compound with hydrogen gas, and double-charged nitrogen and carbon ions at higher levels of RF power. In this study, we reduced baseline interferences in Ar plasma using a cool plasma ($800 W) technique with a X-type cone. Lithium was separated using a cation exchange column (BioRad AG50W-X8, 200-400 mesh) with a mixture of 6 N HNO 3 and 80% methanol at <0.2 mL min À1 elution speed. The short-term reproducibility of d 7 Li values of the NASS-5 seawater standard was 30.55 AE 0.45& (2s, n ¼ 15). Measured d 7 Li values of rock and seawater standards ranged from 2.48 to 30.55&, in good agreements with reported values.

The geographical origin of agricultural products has been intensively studied, but links between agricultural products and the environments are poorly established. Soils, water (streamwater and groundwater), and plants (hot pepper, Capsicum annuum; and rice, Oryza sativa) were collected from all regions of South Korea and measured Sr isotope ratios ((87)Sr/(86)Sr). Sequential leaching of soil showed that Sr in the exchangeable and carbonate fractions (bioavailable) had a lower (87)Sr/(86)Sr ratio than that in the silicate fraction, consistent with a low (87)Sr/(86)Sr ratio in the plant. Although the bedrock-soil-water-plant system is closely linked, statistical analysis indicated that (87)Sr/(86)Sr ratios of the plant showed the greatest agreement with those of water and the exchangeable fraction of soil. This study is the first report of (87)Sr/(86)Sr isoscapes in South Korea and first demonstrates that the agricultural product is strongly linked with the exchangeable fraction of soil and water.