Figure 10
The relationships between δ18Oc(VSMOW) and δ18Odw values are shown for all sampled individuals (n = 75). Colours indicate the country of residence, and shapes indicate the type of drinking water sampled for its δ18Odw value. The different line types show the regression line between δ18Oc and δ18Otap values for Eq. (5): δ18Oc(VSMOW) = 0.11 (± 0.09) x δ18Otap(VSMOW) + 23.29 (± 0.98); [df = 32; \(\overline{R }\)2 = 0.01], δ18Odw values including both tap and surface water values for Eq. (6): δ18Oc(VSMOW) = 0.16 (± 0.08) × δ18Odw_1(VSMOW) + 23.77 (± 0.82); [df = 35; \(\overline{R }\)2 = 0.09] and δ18Odw values for all samples for Eq. (7): δ18Oc(VSMOW) = 0.15 (± 0.07) x δ18Odw_2(VSMOW) + 23.65 (± 0.78); [df = 37; \(\overline{R }\)2 = 0.08]. The solid grey line represents the regression line between δ18Oc and δ18OOIPC values; Eq. (8): δ18Oc(VSMOW) = 0.43 (± 0.05) × δ18OOIPC(VSMOW) + 26.92 (± 0.46); [df = 73,\(\overline{R }\)2 = 0.51].
