carbon isotope Argentina 22 stable isotope 18 nitrogen isotope 10 isotopic analysis 8 Carbon isotopes 6 Cetacea 6 Isotopes 6 South America 6 Stable isotopes 6 chemical composition 6 nonhuman 6 Atlantic Ocean 4 Atlantic Ocean (South) 4 Carbon dioxide 4 Entre Rios 4 Groundwater 4 Groundwater flow 4 Gualeguaychu 4 Isotopic composition 4 Municipal solid waste 4 Solid wastes 4 Southern Ocean 4 article 4 carbon 13 4 carbon dioxide 4 collagen 4 diet 4 dissolved inorganic carbon 4 drug effect 4