Iodine isotopes (¹²⁹I and ¹²⁷I) in the baltic proper, kattegat, and skagerrak basins

Radioactive anthropogenic pollution has raised concerns about the present and future environmental status of the semienclosed Baltic Sea. We here study the distribution and inventory of the anthropogenic radioactive ¹²⁹I in water depth profiles collected from 16 sites in August 2006 and 19 sites in April 2007 in the Baltic Proper and related Kattegat and Skagerrak basins. The results reveal considerable differences of 1291 concentration in terms of spatial and temporal variability and expose relatively high concentrations in the deep waters. Variability in the concentration of ¹²⁷I, stable natural isotope of iodine, seems to follow changes in the seawater salinity, but in oxygenpoor bottom waters sediment diagenetic release may contribute to the concentration of both isotopes in the water body. Inventory estimates show that ¹²⁹I in August 2006 (24.2 ( 15.4 kg) is higher than that in April 2007 (14.4 ( 8.3 kg) within the southern and central Baltic Proper whereas almost a constant load occurs in the Kattegat Basin. Calculated model inventory shows correspondence to empirical data and provides a guideline for future environmental assessment on the impact of ¹²⁹I load in the studied region.