Fig 5 -

Isoscapes of (A) δ13C, (B) δ15N, and (C) δ34S in South Korea, with sampling locations indicated by open circles and seven metropolitan cities shown by bold lines. Maps were produced using ordinary kriging (OK), a common geostatistical interpolation method using ArcGIS version 10.8 (ESRI, Redlands, CA, USA). The method used in this classification is natural break (Jenks). The administrative boundaries of nine administrative provinces are shown. Provinces are abbreviated as: Gyeonggi (GG), Gangwon (GW), Chungbuk (CB), Chungnam (CN), Jeonbuk (JB), Jeonnam (JN), Gyeongbuk (GB), Gyeongnam (GN), and Jeju (JJ).