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

Iodine-129 has been used as a powerful tool for environmental tracing of human nuclear activities. In this work, a sediment core collected from Jiaozhou Bay, the east coast of China, in 2002 was analyzed for ¹²⁹I to investigate the influence of human nuclear activities in this region. Significantly enhanced ¹²⁹I level was observed in upper 70 cm of the sediment core, with peak values in the layer corresponding to 1957, 1964, 1974, 1986, and after 1990. The sources of ¹²⁹I and corresponding transport processes in this region are discussed, including nuclear weapons testing at the Pacific Proving Grounds, global fallout from a large numbers of nuclear weapon tests in 1963, the climax of Chinese nuclear weapons testing in the early 1970s, the Chernobyl accident in 1986, and long-distance dispersion of European reprocessing derived ¹²⁹I. The very well ¹²⁹I records of different human nuclear activities in the sediment core illustrate the potential application of ¹²⁹I in constraining ages and sedimentation rates of the recent sediment. The releases of ¹²⁹I from the European nuclear fuel reprocessing plants at La Hague (France) and Sellafield (UK) were found to dominate the inventory of ¹²⁹I in the Chinese sediments after 1990, not only the directly atmospheric releases of these reprocessing plants, but also re-emission of marine discharged ¹²⁹I of these reprocessing plants in the highly contaminated European seas.