Anthropogenic ¹²⁹I in seawaters along the north-central part of the English Channel: Levels and tracer applications

The English Channel (the Channel) represents a major sink and transport pathway of anthropogenic radioactive ¹²⁹I. Despite this important role, data concerning the distribution of ¹²⁹I in seawater of the Channel are scarce, and most of existing data are restricted to the eastern part of the Channel. The advection and dispersion of ¹²⁹I from the French coast toward the central and further the English coast, especially in the Channel west of Cap de La Hague, are not fully investigated. We present results of iodine isotopes (¹²⁷I and ¹²⁹I) analyses of surface water samples collected along the central English Channel in October, 2010. The data show high 129I concentrations between Dover Strait and La Hague, followed by a dramatic drop towards the Celtic Sea and reveal the dispersal of ¹²⁹I towards central and northern part of the Channel. Our observation also implies that the entire British coast is contaminated by ¹²⁹I. ¹²⁹I levels in the westernmost English Channel, close to the English coast, may reflect combined influences from La Hague and Sellafield. Evolution of ¹²⁹I between 2005 and 2010 suggests a strong link to temporal marine discharges from La Hague plant. The discharges from the nuclear reprocessing facility have continued since 2010 and thus an ecological evaluation of ¹²⁹I radioactive hazards in the environment of the Channel may be needed.