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

Abstract

Concentrations and species of iodine isotopes (127I and 129I) provide vital information about iodine geochemistry, environmental conditions and water masses exchange in oceans. Despite extensive investigations of anthropogenic 129I in the Arctic Ocean and the Nordic Seas, concentrations of the isotope in the Atlantic Ocean are, however, still unknown. We here present first data on 129I and 127I, and their species (iodide and iodate) in surface water transect along the northeastern Atlantic between 30° and 50°N. The results show iodate as the predominant species in the analyzed marine waters for both 127I and 129I. Despite the rather constant ratios of 127I−/127IO3−, the 129I−/129IO3− values reveal variations that apparently response to sources, environmental conditions and residence time. These findings provide a new tracer approach that will strongly enhance the application of anthropogenic 129I in ocean environments and impact on climate at the ocean boundary layer.

129I and its species in the East China Sea: level, distribution, sources and tracing water masses exchange and movement

“…But it is lower than those in the north Atlantic (31–50°N) ( 129 I concentrations of (4.0–12.7) × 10 7  atoms/L and 129 I/ 127 I ratios of (2–57) × 10 −10 )3. The higher 129 I level in the North Atlantic results from the leakage and southwards dispersion of the high reprocessing derived 129 I water in the English Channel.…”

“…While large amount of 129 I has been released to the environment by human nuclear activities, among them atmospheric nuclear weapons testing (NWT) in 1945–1980 and spent nuclear fuel reprocessing are two major contributions of 129 I in the environment2. The large and well documented 129 I releases and the high residence time of iodine in the ocean make 129 I an ideal oceanographic tracer, a number of studies have been carried out in the North Atlantic and Arctic Oceans using 129 I and its species for water circulation and marine environment investigation345. A few investigation of 129 I in the Pacific Ocean were reported678.…”

Estimation of 129I inventory in the oceans

“…The North Sea 129 I plumes are relatively rapidly (3-5 years) transported into the Arctic Ocean and ventilated into the North Atlantic during a transit time of 7-12 years [7]. Transit time to the southern part of the North Atlantic is suggested to be in access of 15 years from the sources [8] and likely much longer to the southern Oceans. This long transit time and the rather negligible transport of 129 I from the Arctic to the Pacific Ocean suggest that the inventory of 129 I in oceans other than the Arctic and North Atlantic may record mainly fallout from atomic weapon testing and atmospheric releases from the European reprocessing and only minor marine discharges (the period before 2000).…”

Tracing variability in the iodine isotopes and species along surface water transect from the North Sea to the Canary Islands

“…The peaks in the southern part of the transect, however, may attribute to influences of Mediterranean water parcels, which were likely carrying signals of the Marcoule facility releases. Thus, the occurrence of high 129 I and 129 I -/ 129 IO 3 -values probably reflect specific circulation of Mediterranean Overflow Water (MOW) in the Atlantic Ocean [12]. If this suggested explanation is correct, then 129 I and its speciation can potentially be applied as sensitive tracers to label MOW in the intermediate layer of North Atlantic.…”

“…This sampling program was a part of 2010/2011 Antarctica two-ship expedition, which was an international scientific cruise jointly funded by the Swedish Polar Research Secretariat and the US National Science Foundation (NSF). Part of the expedition was aimed at investigating iodine isotopes ( 129 I and 127 I) and species of iodine (I -and IO 3 -) variability in surface water along transect from the North Sea through the English Channel and Northeastern Atlantic and some of the preliminary data have been published elsewhere [12][13][14]. The sampling transect covered the North Sea, the English Channel and the Northeastern Atlantic Ocean to the Canary Island (Fig.…”