129I record of nuclear activities in marine sediment core from JiaozhouBay 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&nbsp;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.</p

Progress on I-129 analysis and its application in environmental and geological researches

Iodine-129 is a naturally generated isotope, but anthropogenic releases are the dominated source of I-129 in the present environment. Among many measurement techniques, neutron activation analysis (NM) and accelerator mass spectrometry (AMS) are only methods used for measurement of I-129 in environmental level. Based on its source terms, chemical properties and environmental behaviors, I-129 can be applied for geological dating in a range of 2-80 Ma, investigation of formation and migration of hydrocarbon, circulation of ocean water, atmospheric process of iodine, as well as reconstruction of dispersion and migration of short-lived radioisotopes of iodine released from nuclear accidents. This article aims to summarize and critically compare the analytical techniques used for I-129 measurement and chemical methods for separation of iodine from various sample matrices, purification from the interferences, as well as preparation of suitable target for AMS measurement. The major applications in environmental and geological researches are reviewed, which mainly focus on the new progress and potential development in the future. The application of I-129 in the investigation of radioactive contamination from the Fukushima accident is discussed.</p

Analysis of low-level I-129 in brine using accelerator mass spectrometry

An improved solvent extraction procedure for iodine separation from brine samples has been applied at Xi&#39;an Accelerator Mass Spectrometry (AMS) center. Oil in the brine sample has to be removed to avoid appearance of the third phase during solvent extraction and to improve the chemical yield of iodine. The small amount of oil remained in the water phase was first removed by phase separation through settling down sufficiently based on their immiscibility, and then by filtration through a cellulose filter, on which oil was absorbed and removed. After oil removed, extraction recovery of iodine could achieve more than 90 %. The sodium bisulfite as an effective reductant should be added before acidification to avoid loss of iodine by formation of I-2 in sample via reaction of iodate and iodide at pH 1-2, and then pH was adjusted to 1-2 to reduce the iodate to iodide followed by oxidation of iodide to I-2 and solvent extraction to separate all inorganic iodine. As a pre-nuclear era sample, I-129/I-127 ratio in brine is normally more than two orders of magnitude lower than that in present surface environmental samples, so prevention of cross-contamination and memory effect in apparatus during processing procedure are very critical for obtaining reliable results, and monitoring the procedure blank is very important for analytical quality of I-129. The I-129/I-127 isotopic ratio in the brine samples and procedure blank of iodine reagents were measured to be (1.9-2.7) x 10(-13) and 2.08 x 10(-13), respectively, 3-4 orders of magnitudes lower than that in environmental samples in Xi&#39;an, and the result of procedure blank is in the same level as the previous experiments in past 3 years, indicating contamination is not observed in our method.</p

129I assessment reveals the impact of Fukushima incidenton Dapeng Peninsula, Shenzhen, China

In order to assess the radioactive impact of Fukushima Incident on the coastal environment of Dapeng Peninsula, Shenzhen, China, combining accelerator mass spectrometry with epithermal neutron activation analysis, we measured the 129I/127I ratios and 129I levels in surface seawater, oyster (Ostrea gigas) and kelp (Sargassum henslouianum). The results showed that the influence of Daya Bay Nuclear Power Base was ignorable to local environment, but the Fukushima Incident had caused significant increase of 129I levels in oyster (P&nbsp;&lt;&nbsp;0.001) and kelp (P&nbsp;&lt;&nbsp;0.05) from Dapeng Peninsula between Jun-2011 and Apr-2012. However, the 129I levels in oyster and kelp were far below the guideline given by Codex Alimentarius Commission and would not cause immediate harm to the health of local residents.</p

Level and source of 129I of environmental samples in Xi'an region, China

Iodine-129 is widely used as a tracer in various environmental practices such as monitoring of nuclear environmental safety, seawater exchange and transport, geochemical cycle of stable iodine and dating of geological events. The spatial distribution of (129)I concentration varies significantly on global scale because of anthropogenic input from nuclear activities coupled with scarcity of data on environmental (129)I variability in many parts of the world including Asia. Here we report new data on (129)I and (127)I concentrations in soil, vegetation, river water and precipitation collected from Xi&#39;an area, China. The results indicate values for environmental (129)I/(127)I ratios in the investigated area range from 1.1 x 10(-10) to 43.5 x 10(-10) with a mean of 20.6 x 10(-10), which is 1-3 orders of magnitude lower than the ratios observed in Europe, but comparable with those observed in the locations far from direct effect of point release sources and at similar latitude. The main source of (129)I in the investigated area is attributed to the global fallout of both atmospheric nuclear weapons testing and long distance dispersion of fuel reprocessing releases. (C) 2011 Elsevier B.V. All rights reserved.</p