¹²⁷I and ¹²⁹I Species and Transformation in the Baltic Proper, Kattegat, and Skagerrak Basins

Abstract

Occurrence of anthropogenic (129)I in seawater has provided invaluable information about water circulation and exchange rates, but results on (129)I species (iodide and iodate) are limited and only available for surface water. We here present the first extensive results on (129)I and (127)I species in samples of seawater depth profiles, which were collected in August 2006 and April 2007 in the Skagerrak, Kattegat, and Baltic Proper. The results expose ≤10% annual reduction of iodate as (129)I is transported from the English Channel along the Dutch coast and German Bight into the Skagerrak and Kattegat. The results also suggest strong variability between surface and bottom seawater with respect to the predominant iodine species. Distribution of iodide and iodate of both (127)I and (129)I in the Kattegat mainly reflects water mixing process rather than speciation transformation. In water of the Baltic Proper, high (127)I(-)/(127)IO(3)(-) and (129)I(-)/(129)IO(3)(-) values suggest effective reduction of iodate with a maximum rate of 8 × 10(-7) ((127)IO(3)(-)) and 6 × 10(-14) ((129)IO(3)(-)) (g/m(3).day). The reduction process of iodate seems to be related to decomposition of organic matter and photochemically induced reactions.

Speciation of <sup>127</sup>I and <sup>129</sup>I in atmospheric aerosols at Risø, Denmark: insight into sources of iodine isotopes and their species transformations

“…Only a small fraction of 129 I (about 0.5-2 kg year −1 after 2004 and 3-10 kg yr −1 in 1981-2004) has been released as gaseous form to the atmosphere and dispersed over a large area, in particular in Europe (Schnabel et Ernst et al, 2003;Persson et al, 2007;Jabbar et al, 2012). Aqueous 129 I was carried by ocean currents and transported to the North Sea, Kattegat, and Baltic Sea, and continues to the Arctic along the Norwegian coast (Alfimov et al, 2004a;Buraglio et al, 1999;Hou et al, 2007;Raisbeck et al, 1995;Yi et al, 2012). Remarkably elevated 129 I concentrations of up to 10 10 -10 11 atoms L −1 have been found in the North Sea (with 129 I / 127 I atomic ratios of 10 −7 -10 −6 ), 10 9 -10 10 atoms L −1 in Norwegian coastal waters and the Kattegat (with 129 I / 127 I atomic ratios of 10 −8 -10 −7 ), and 10 8 -10 9 atoms L −1 in the Baltic Sea (Aldahan et al, 2007;Alfimov et al, 2004b;He et al, 2014;Hou et al, 2007;Michel et al, 2012;Yi et al, 2011).…”

129I record of nuclear activities in marine sediment core from Jiaozhou Bay in China

“…Recent studies have unraveled the complicated physical and chemical pathways that distinguish 129 I from natural 127 I in a range of environments. Speciation analysis of both isotopes from the same samples provides a comprehensive picture of the sources and pathways followed by the two isotopes (He et al, 2014;He et al, 2013;Hou et al, 2007;Hou et al, 2000;Yi et al, 2012). The levels observed in surface environmental samples are, in general, stacked signals with contributions from a number of historical sources.…”

Iodine isotopes species fingerprinting environmental conditions in surface water along the northeastern Atlantic Ocean

“…This potential has been successfully applied in the North Sea and the Baltic Sea101112. However, at present we have no idea on distribution and conversion patterns of 129 I species in the open sea environment.…”