Water Circulation and Marine Environment in the Antarctic Traced by Speciation of 129I and 127I

127I and 129I species in the English Channel and its adjacent areas: Uncovering impact on the isotopes marine pathways

Radioactive iodine-129 has been released from the La Hague nuclear fuel reprocessing facility (NRF) into the English Channel, but the distribution and transformation of the isotope species, and environmental consequences have not been fully characterized in the Channel. Here we present data on iodine isotopes (¹²⁹I and ¹²⁷I) species in surface water of the English Channel and the southern Celtic Sea. Compared to ¹²⁷I species, the concentrations of ¹²⁹I^- and ¹²⁹IO₃^- show more variations, but iodate is the major species for both ¹²⁹I and ¹²⁷I. Our data provide new information regarding iodide-iodate inter-conversion showing that water dilution and mixing are the main factors affecting the ¹²⁷I and ¹²⁹I species distribution in the Channel. Some reduction of iodate occurs within the English Channel and mainly in the west part because of biotic processes. The ¹²⁹I species transformation is overall insignificant, especially in the eastern Channel, where a constant value of ¹²⁹IO₃^-/¹²⁹I is observed, which might characterize the La Hague wastewater signal. In the Celtic Sea, oxidation of iodide can be traced by ¹²⁷I and ¹²⁹I species. On a larger scale, ¹²⁹I generally experienced an oxidation process in the Atlantic Ocean, while in the coast of shallow shelf seas, new produced ¹²⁹I^- can be identified, especially in the German Bight and the Baltic Sea. The data of ¹²⁹I species in the English Channel can provide estimate of redox rates in a much broader marine areas if the transit time of ¹²⁹I from La Hague is well-defined. Furthermore, estimate of inventories for ¹²⁹I and its species in the Channel, and fluxes of ¹²⁹I species from the English Channel to the North Sea add important information to the geochemical cycle of ¹²⁹I.

129I in rainwater across Argentina

Concentrations of ¹²⁷I and ¹²⁹I in rainwater samples from several stations across Argentina (latitudes between 25° S and 55° S) were measured and analyzed for the assessment of distribution patterns and potential sources of ¹²⁹I in the Southern Hemisphere. Measured ¹²⁹I levels, clearly above those explainable by natural background and atmospheric nuclear weapons tests, can be understood by the injection into the Southern Hemisphere of ¹²⁹I that had been discharged from nuclear fuel reprocessing plants in the Northern Hemisphere.

Tracing the upwelling process in the northern Benguela upwelling system (nBUS) by 129I

New data on the presence of ¹²⁹I in seawater in the Southern Hemisphere measured by Accelerator Mass Spectrometry (AMS) is presented. The samples were collected in 2014 along the Namibian coast during a cruise organised by the National Marine Information and Research Centre (NatMIRC), the national laboratories of the Ministry of Fisheries and Marine Resources (MFMR) in Namibia, and the IAEA Environment Laboratories (IAEA NAEL) in Monaco. The Benguela upwelling system is known as one of the most important marine upwelling regions in the world. Strong winds induce an offshore transport of surface seawater which is substituted by cool subsurface water inshore. As this water is nutrient-rich, which leads to high primary productivity, the Benguela upwelling system has a very important role as a fishing production area. The ¹²⁹I concentrations in samples were between (0.66 ± 0.14) × 10⁷ and (1.45 ± 0.30) × 10⁷ atoms/kg. The highest ¹²⁹I concentrations were found in the offshore surface samples. Deep-sea and inshore samples contained lower ¹²⁹I concentrations, possibly as an effect of the upwelling process. A comparison with previously published studies suggests that the presence of ¹²⁹I in the northern Benguela upwelling system (nBUS), is mainly due to the impact of nuclear weapons global fallout, without any evident impact of nuclear fuel reprocessing.

Antarctic Futures: An Assessment of Climate-Driven Changes in Ecosystem Structure, Function, and Service Provisioning in the Southern Ocean

In this article, we analyze the impacts of climate change on Antarctic marine ecosystems. Observations demonstrate large-scale changes in the physical variables and circulation of the Southern Ocean driven by warming, stratospheric ozone depletion, and a positive Southern Annular Mode. Alterations in the physical environment are driving change through all levels of Antarctic marine food webs, which differ regionally. The distributions of key species, such as Antarctic krill, are also changing. Differential responses among predators reflect differences in species ecology. The impacts of climate change on Antarctic biodiversity will likely vary for different communities and depend on species range. Coastal communities and those of sub-Antarctic islands, especially range-restricted endemic communities, will likely suffer the greatest negative consequences of climate change. Simultaneously, ecosystem services in the Southern Ocean will likely increase. Such decoupling of ecosystem services and endemic species will require consideration in the management of human activities such as fishing in Antarctic marine ecosystems.

Spatial and vertical distribution of 129I and 127I in the East China Sea: Inventory, source and transportation

Iodirne-129 is useful for tracking water mass movement in the ocean. In this study, the concentration of iodine isotopes in seawater of the East China Sea (ECS) in October 2013 were analyzed to investigate the spatial and vertical distribution of ¹²⁹I and ¹²⁷I to understand water mass exchange. Results showed that the ¹²⁹I/¹²⁷I atomic ratios varied with the water mass, with higher values of (10-20) × 10^-11 in the coastal regions and lower values of <8 × 10^-11 offshore. Inventories of ¹²⁹I were estimated to be (0.23-1.7) × 10¹² atoms m^-2 (n = 18) in upper 100 m waters, which is comparable to those of other regions without being contaminated by the nuclear accidents or nuclear reprocessing facilities. The total amount of ¹²⁹I in the ECS water column was estimated to be 88 g in which over 90% is attributed to the oceanic input (e.g., West Pacific) via the Kuroshio Current (KC). The contributions of ¹²⁹I from Changjiang (Yangtze River) terrestrial watershed (<7.5%) and atmospheric fallout (<2.7%) were small. Those from the Fukushima accident were negligible during this investigation. The ¹²⁹I/¹²⁷I ratios versus salinity distribution showed the range and stratification of the Changjiang, Yellow Sea, and KC waters in the ECS. Our study shows that the Changjiang fresh water could be transported to the North Jiangsu coast in October; the Taiwan Warm Current water could intrude to Northern part of the Changjiang Estuary (32°N). Besides, our results suggest that the ¹²⁹I/¹²⁷I profile is useful to indicate the seawater mixing process in ocean marginal systems.