Iodine-129 in animal thyroids from Argentina

129I and 127I concentrations in animal thyroids coming from several regions of Argentina were determined by accelerator mass spectrometry (AMS) and gas chromatography (GC), respectively. The measured 129I/127I ratios, ranging from 3×10−12 to 4×10−10, are significantly lower than those typical for areas in the northern hemisphere (10−10–10−7). The 129I concentrations show a clear dependence with latitude and season, which can be understood considering tropospheric circulation patterns, possible 129I sources and regional precipitation rates. ► This is the first determination of 129I in thyroids from the southern hemisphere via AMS. ► Isotopic ratios measured are lower than those found in areas of the northern hemisphere. ► Two samples represent 129I/127I ratios similar to pre-anthropogenic values. ► Our data show a clear dependence with latitude and season, related with deposition pathways. ► We find a strong decorrelation between 129I and iodine sources.