Source Of 129I Research Articles

Reconstruction of the Sources and Their Contributions to 129I in Northern Xinjiang, China.

Anthropogenic 129I, as a long-lived fission product and volatile radionuclide, can be used to investigate dispersion of air masses and the deposition of atmospheric pollution. Surface soil and soil core samples were collected from Northern Xinjiang and analyzed for 127I and 129I. The results show that 129I/127I atomic ratios in surface soil are inhomogeneous with a range of (2.07-106) × 10-9, and the maximum values in each soil core occurred at surface-subsurface layers (0-15 cm) at undisturbed sites. The dominant source of 129I in Northern Xinjiang is European nuclear fuel reprocessing plant (NFRP) releases, accounting for at least 70% of the total inventory; less than 20% of 129I originates from the global fallout of atmospheric nuclear weapons tests; less than 10% comes from the regional deposition of nuclear weapons tests at the Semipalatinsk site; and the regional deposition from the nuclear weapons tests at the Lop Nor site is insignificant. The European NFRP-derived 129I was transported to Northern Xinjiang via long-distance atmospheric dispersion with the westerlies through Northern Eurasia. The distribution of 129I in the surface soil in Northern Xinjiang is mainly controlled by topography, wind fields, land utilization, and vegetation coverage.

Iodine cycling in the subarctic Pacific Ocean: Insights from 129I

As the largest iodine reservoir on the Earth’s surface, the ocean plays a vital role in global iodine cycling. Here, we present results on concentrations of stable- and radio-iodine (127I and 129I) of total iodine (TI), iodide (I–), and iodate (IO3–) in seawater samples collected in the top 800 m of the subarctic Pacific Ocean. The speciation distributions of both 127I and 129I showed large variations in depth and geographical location. The T127I concentrations ranged from 321 to 484 nM, were lower at the surface, and increased with depth. In all depth profiles of T129I, the maximum concentrations occurred in the subsurface layer, below which, the T129I concentrations decreased with depth and ranged from 0.2 to 2.1 × 107 atoms/L. Besides, the 129I/127I atom ratios in iodide were significantly higher than those in iodate. It can be inferred from existing research that anthropogenic 129I from atmospheric deposition is the overwhelming source of 129I in the subarctic Pacific Ocean. On this basis, we successfully simulated the 129I vertical dispersion using a one-dimensional vertical diffusion model. The unbalanced distribution of 129I among different iodine species provided useful information for demonstrating the inevitability of the oxidation process of iodide in nature, although whether this oxidation occurred in the ocean remains to be further explored, and the indispensable contribution of iodate to the iodine removal processes in the upper ocean. Our study suggests that anthropogenic 129I can be used as an effective intrinsic tracer for the study of iodine cycling.

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.

Circulation of Circumpolar Deep Water and marine environment traced by 127I and 129I speciation in the Amundsen Sea Polynya, Antarctica

The long-lived anthropogenic 129I released from human nuclear activities has been widely employed as an effective oceanographic tracer to investigate circulation of water masses in marine environment. Depth profiles of seawater collected from the Amundsen Sea Polynya, Antarctica were analyzed for total 129I and 127I, as well as their species of iodide and iodate. The measured 129I concentrations ((1.15–3.43) × 106 atoms/L) and 129I/127I atomic ratios ((0.53–1.19) × 10−11) indicate that anthropogenic 129I has not only reached the Antarctic surface marine environment but also the deep water due to a strong vertical mixing of water masses. The Circumpolar Deep Water (CDW) flowed southward along continental shelf towards the ice shelf zone (74.25°S) at a depth of 1025 m and then migrated upward and northward to the polynya and finally to the sea ice zone (71.95°S). The maximum upwelling depth of the CDW was around 200 m in the polynya. The source of 129I− in the polynya is predominantly the intrusion of source waters rather than the in-situ reduction of iodate by phytoplankton, implying a considerably slow reduction process of iodate to iodide in this region.

Temporal variation in <sup>129</sup>I and <sup>127</sup>I in aerosols from Xi'an, China: influence of East Asian monsoon and heavy haze events

Abstract. Aerosol iodine isotopes are pivotal links in atmospheric circulation of iodine in both atmospheric and nuclear sciences, while their sources, temporal change and transport mechanism are still not well understood. This work presents the day-resolution temporal variation in iodine-129 (129I) and iodine-127 (127I) concentrations in aerosols from Xi'an, north-west China, during 2017/18. Both iodine isotopes have significant fluctuations with time, showing the highest levels in winter, approximately 2–3 times higher than in other seasons, but the correlation between 129I and 127I concentrations reflects that they have different sources. Aerosol 127I concentrations are found to be noticeably positively correlated with air quality index and five air pollutants. Enhanced fossil fuel combustion and inverse weather conditions can explain the increased concentrations and peaks of 127I in winter. The change in 129I concentrations confirms that the source and level of 129I in the monsoonal region were alternatively dominated by the 129I-enriched East Asian winter monsoon and the 129I-poor East Asian summer monsoon. The mean 129I∕127I number ratio of (92.7±124)×10-10 provides an atmospheric background level for the purpose of nuclear environmental safety monitoring. This study suggests that locally discharged stable127I and externally input 129I are likely involved in fine particles formation in urban air, which provides insights into the long-range transport of air pollutants and iodine's role in particulate formation in urban atmosphere.

Iodine isotopes (129I and 127I) in the hydrosphere of Qinghai-Tibet region and South China Sea

The radioactive isotope 129I, with a half-life of 1.57 × 107 years, is widely used as a tracer to assess nuclear safety, to track environmental and geological events and to figure out the details of the stable iodine geochemical cycle. This work investigated the 129I and 127I distribution in water samples collected from the terrestrial (rivers, lakes and springs) and marine water systems (estuary and sea) in China. The measured 129I concentrations of (1–51) × 106 atoms/L and 129I/127I ratios of (0.03–21) × 10−10 shows the variability of 129I level in the water systems. The local permafrost and seasonal frozen environment play a key role in groundwater recharge in the Qinghai-Tibet region, which is reflected in the 129I distribution in surface water. The depth distribution of 129I in the water column of the South China Sea reflects the effluence of different currents. The results also indicate that the hydrosphere of China contains one to three orders of magnitude less 129I compared to those reported in Europe. Despite the large distance, the European nuclear fuel reprocessing facilities represent the major source of 129I in the hydrosphere of China through atmospheric transport. The contribution of the Fukushima nuclear accident to 129I levels in the hydrosphere of China was negligible.

Impacts of anthropogenic source from the nuclear fuel reprocessing plants on global atmospheric iodine-129 cycle: A model analysis

Abstact The long-lived radioactive iodine (129I) is a useful geochemical tracer of radioactivity in the atmospheric environment. Although the behavior of 129I in the atmosphere is still not fully known because of lack of continuous monitoring, we recently observed clear seasonal trends in air concentration and deposition of 129I in Japan. Using these data, we developed a global atmospheric 129I transport model to reveal key processes for the global atmospheric 129I cycle. The physical and chemical processes of advection, turbulent diffusion, dry and wet deposition, atmospheric photolysis, gas–particle conversion in the atmosphere, anthropogenic sources of 129I discharged from operating nuclear fuel reprocessing plants, and natural sources of 129I volatilized from ocean and land were included into the model. The model generally reproduced the observed seasonal change in monthly air concentration and deposition of 129I in Japan, and the global distribution of 129I concentration in rain as presented in past literature. Numerical experiments changing the intensity of anthropogenic and natural sources were conducted to quantify the impact of anthropogenic sources on the global 129I cycle. The results indicated that the atmospheric 129I from the anthropogenic sources was readily deposited in winter and can be accumulated mainly in the northern part of Eurasia. In contrast, the atmospheric 129I from the natural sources dominated the deposition in summer. These results suggested that the re-emission process of 129I from the Earth's surface may be important as a secondary impact of 129I in the global-scaled environment. Furthermore, although wet deposition dominated the total deposition in the Northern hemisphere, dry deposition regionally and seasonally contributed to the total deposition over arctic and northern part of Eurasia in winter, suggesting that the dry deposition may play a key role in the seasonal change of 129I deposition in the high latitudes of the Northern hemisphere.

Impact of North Korean nuclear weapons test on 3 September, 2017 on inland China traced by 14C and 129I

Environmental impact of North Korea nuclear weapons testing on 3 Sept, 2017, is of key concern. In order to investigate whether there is radioactive leakage and whether it can be transported to inland China, 14C and 129I are determined in aerosol samples collected in a Chinese inland city before and after the test. Aerosol Δ14C values before and after the test do not show any significant difference. In contrast, a four-fold increase of 129I/127I ratios was found after the test. The possible sources of 129I in these atmospheric samples and the impact of the North Korea nuclear test are discussed.

A 60-year record of 129I in Taal Lake sediments (Philippines): Influence of human nuclear activities at low latitude regions

The influence of human nuclear activities on environmental radioactivity is not well known at low latitude regions that are distant from nuclear test sites and nuclear facilities. A sediment core collected from Taal Lake in the central Philippines was analyzed for 129I and 127I to investigate this influence in a low-latitude terrestrial system. A baseline of 129I/127I atomic ratios was established at (2.04–5.14) × 10−12 in the pre-nuclear era in this region. Controlled by the northeasterly equatorial trade winds, increased 129I/127I ratios of (20.1–69.3) × 10−12 suggest that atmospheric nuclear weapons tests at the Pacific Proving Grounds in the central Pacific Ocean was the major source of 129I in the sediment during 1956–1962. The 129I/127I ratios, up to 157.5 × 10−12 after 1964, indicate a strong influence by European nuclear fuel reprocessing plants. The East Asian Winter Monsoon is found to be the dominant driving force in the atmospheric dispersion of radioactive iodine (129I) from the European nuclear fuel reprocessing plants to Southeast Asia, which is also important for dispersion of other airborne pollutants from the middle-high to low latitude regions. A significant 129I/127I peak at 42.8 cm in the Taal Lake core appears to be the signal of the Chernobyl accident in 1986. In addition, volcanic activities are reflected in the iodine isotope profiles in the sediment core, suggesting the potential of using iodine isotopes as an indicator of volcanic eruptions.

Reconstructing surface ocean circulation with 129I time series records from corals

The long-lived radionuclide 129I (half-life: 15.7 × 106 yr) is well-known as a useful environmental tracer. At present, the global 129I in surface water is about 1–2 orders of magnitude higher than pre-1960 levels. Since the 1990s, anthropogenic 129I produced from industrial nuclear fuels reprocessing plants has been the primary source of 129I in marine surface waters of the Atlantic and around the globe. Here we present four coral 129I time series records from: 1) Con Dao and 2) Xisha Islands, the South China Sea, 3) Rabaul, Papua New Guinea and 4) Guam. The Con Dao coral 129I record features a sudden increase in 129I in 1959. The Xisha coral shows similar peak values for 129I as the Con Dao coral, punctuated by distinct low values, likely due to the upwelling in the central South China Sea. The Rabaul coral features much more gradual 129I increases in the 1970s, similar to a published record from the Solomon Islands. The Guam coral 129I record contains the largest measured values for any site, with two large peaks, in 1955 and 1959. Nuclear weapons testing was the primary 129I source in the Western Pacific in the latter part of the 20th Century, notably from testing in the Marshall Islands. The Guam 1955 peak and Con Dao 1959 increases are likely from the 1954 Castle Bravo test, and the Operation Hardtack I test is the most likely source of the 1959 peak observed at Guam. Radiogenic iodine found in coral was carried primarily through surface ocean currents. The coral 129I time series data provide a broad picture of the surface distribution and depth penetration of 129I in the Pacific Ocean over the past 60 years.

Historical record of nuclear activities from 129I in corals from the northern hemisphere (Philippines)

Iodine-129 is a long-lived fission product that is majorly released in human nuclear activities (HNA) such as nuclear bomb testing, nuclear fuel reprocessing, and nuclear accidents. It is a good environmental tracer and former measurements of 129I in corals from the southern hemisphere show the increasing trend of 129I concentrations in the marine environment caused by HNA. Here we show time series of 129I/127(stable)I isotopic ratios in two coral cores from the northern hemisphere (Philippines) and how these record 129I released from HNA in even greater, unprecedented detail. Corals were taken from the Pacific Ocean (Baler) and South China Sea (Parola) sides of the Philippines. We observed nearly identical peaks (129I/127I ∼ 31.5 × 10−12) in both the Baler and Parola records, each attributed to the year 1962 – the year with the highest recorded amount of 129I release from nuclear bomb testing. This 1962 129I bomb signal offers a new time marker that can be used to establish or confirm age models of corals, comparable to or possibly better than the well-known coral 14C bomb peak. We also observed nuclear fuel reprocessing and Chernobyl accident 129I signals in years 1977, 1980, and 1986, concurrently in Parola and with 9 to 11-year lags in Baler. This discrepancy in timing suggests that 129I was transported to the South China Sea and Pacific Ocean sides of the Philippines directly from the atmosphere and through prevailing ocean currents, respectively. Lastly, we observed surprisingly high 129I/127I isotopic ratios (i.e., 22.8 to 38.9 × 10−12) in the Parola record after the year 1996, which is in contrast to the decreasing trend observed in the Baler record and in published 129I releases of different HNA. These results possibly indicate the presence of unknown sources of 129I in the South China Sea region.

Iodine-129, Iodine-127 and Cesium-137 in seawater from the North Sea and the Baltic Sea

In this study, new data are presented for the iodine isotopes (127I, 129I and their isotopic ratios) and Cesium (137Cs) in water samples of the North Sea and the Baltic Sea in 2005 and 2009. This study supplements and extends the study of Michel et al. (2012). Iodine isotopes were separated from their matrix by using an anion exchange method and were determined by applying ICP-MS and AMS. 137Cs in seawater was determined after cesium ion exchange procedure enrichment by gamma-spectrometry. The concentrations of 127I in seawater of the North and Baltic Sea are fairly constant in each Sea with averages of (44 ± 2) and (21 ± 1) ng g−1, respectively, depending on the salinity. However, large variations of 129I concentrations in these areas were detected, which decreased along the French, Belgian, Dutch, German, and Danish shores. 129I/127I isotope ratios in the Baltic Sea are about 10 times lower than in the North Sea in 2009. The highest isotopic ratios (2.7 × 10−6) was detected in the English Channel east of the nuclear reprocessing plant at Cap de la Hague. The results confirm the result of our early study that the sources of 129I in the North Sea are primarily the nuclear reprocessing facilities at Sellafield (UK) and La Hague (F), and that in the Baltic Sea the inflow of water from North Sea through the Danish Straits dominates the occurrence of 129I.In 2009, the activity concentration of 137Cs was at least 6 times higher in the Baltic Sea (37 Bq m−3) than in the North Sea (5.9 Bq m−3), due to release of 137Cs from sediments in the Baltic Sea, which were contaminated by the Chernobyl accident and – to a minor degree – the atmospheric explosions of atomic bombs. The results are discussed by comparing the results of our previous work and the current study demonstrating the continuing disequilibrium of 129I/127I atomic ratio in the environmental compartments.

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.

Distribution and source of 129I, 239,240Pu, 137Cs in the environment of Lithuania

Fifty five soil samples collected in the Lithuania teritory in 2011 and 2012 were analyzed for 129I, 137Cs and Pu isotopes in order to investigate the level and distribution of artificial radioactivity in Lithuania. The activity and atomic ratio of 238Pu/239,240Pu, 129I/127I and 131I/137Cs were used to identify the origin of these radionuclides. The 238Pu/239+240Pu and 240Pu/239Pu ratios in the soil samples analyzed varied in the range of 0.02–0.18 and 0.18–0.24, respectively, suggesting the global fallout as the major source of Pu in Lithuania. The values of 10−9 to 10−6 for 129I/127I atomic ratio revealed that the source of 129I in Lithuania is global fallout in most cases though several sampling sites shows a possible impact of reprocessing releases. Estimated 129I/131I ratio in soil samples from the southern part of Lithuania shows negligible input of the Chernobyl fallout. No correlation of the 137Cs and Pu isotopes with 129I was observed, indicating their different sources terms. Results demonstrate uneven distribution of these radionuclides in the Lithuanian territory and several sources of contamination i.e. Chernobyl accident, reprocessing releases and global fallout.

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

A complete transect of surface water samples from the North Sea to the Canary Islands was collected during a continuous period in 2010. The samples were analyzed for total 129I and 127I isotopes and their iodide and iodate species. The results indicate a large variability in the total 129I and its species along the transect, whereas less change and variation are observed for the total 127I and its species. Transport of 129I from the western English Channel via Biscay Bay is the main source of 129I in the northeastern Atlantic Ocean.

Iodine-129 in water samples collected adjacent to a spent nuclear fuel reprocessing plant in Rokkasho, Japan

The spent nuclear fuel reprocessing plant in Rokkasho, Japan, has been undergoing final testing since March 2006. The concentrations of 129I in environmental water samples collected around the reprocessing plant were measured from 2005 to 2012. The 129I concentrations in water samples of the brackish lake adjacent to a plant from 2006 to 2008 which the spent fuel rods were cut and chemically processed, was higher than the background level. The major source of 129I in the lake was dominated by the direct deposition of 129I from the atmosphere than that from the ocean.

129I dispersion and sources in Northwest Canada

Radioiodine, 129I is a biophilic and mobile radionuclide, and a major contaminant of concern for long term radioactive waste disposal. Nuclear fuel reprocessing has released large amounts of anthropogenic 129I in a number of locations globally; this has led to an increase in the concentration of 129I and the 129I/127I ratio in the environment. Therefore, a detailed understanding of its movement and concentration in the environment is essential. While 129I dispersion has been examined in the vicinity of nuclear activities, little is known about its accumulation in remote regions. Accordingly, we have undertaken reconnaissance sampling in the Arctic as a location that may be affected by 129I fallout. Samples from large watersheds were collected in northern Canada on a trajectory starting in Whitehorse, Yukon Territory (60°43′00″N) and moving north to Tsiigehtchic, Northwest Territory (67°26′26″N). Results show concentrations of 129I up to 27×106atoms/L are present in Northwest Canada and 129I/I ratios up to 1.68×10−10. Annual 129I fallout ranges from 2.78×109 to 7.95×109atoms/m2/yr, calculated by normalizing the measured values to watershed area and discharge. These quantities substantially exceed literature values for waters containing only geogenic or cosmogenic production and are similar for all watersheds regardless of watershed area or discharge. Anthropogenic releases of 129I into the atmosphere or oceans are the major potential sources of 129I in the Arctic.

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

Iodine-129 is a naturally generated isotope, but anthropogenic releases are the dominated source of 129I in the present environment. Among many measurement techniques, neutron activation analysis (NAA) and accelerator mass spectrometry (AMS) are only methods used for measurement of 129I in environmental level. Based on its source terms, chemical properties and environmental behaviors, 129I can be applied for geological dating in a range of 2–80Ma, 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 129I 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 129I in the investigation of radioactive contamination from the Fukushima accident is discussed.

Iodine-129, Iodine-127 and Caesium-137 in the environment: soils from Germany and Chile

Soil profiles from Bavaria in southern Germany and from Chile were analysed for 129I by accelerator mass spectrometry (AMS), for 127I by inductively coupled plasma mass spectrometry (ICP-MS), and for 137Cs by gamma-spectrometry. The mean deposition density of 137Cs in soils from Bavaria was (41×1.5±1)kBqm−2 (geometric mean and geometric standard deviation), originating mostly from the Chernobyl fall-out. The deposition density of 129I in these soils was (109×1.5±1)mBqm−2. The dominant sources of 129I in Bavaria are, however, the reprocessing plants La Hague and Sellafield and not the Chernobyl fall-out. The 129I/127I isotopic ratios of the Bavarian soils were between 10−7 and 10−10, i.e. 102–105 times higher than the ratios observed for the samples from Chile. The 129I integral deposition densities in Chile, Easter Island and Antarctica were between 0.3mBqm−2 and 2mBqm−2. In these soils, the observed 129I/127I ratios were about 10−12. The soils from Chile allow the determination of the 129I fall-out from the atmospheric nuclear weapons explosions undisturbed from contaminations due to releases from reprocessing plants. An upper limit of the integral 129I deposition density of the atmospheric nuclear weapons explosions on the Southern Hemisphere (27°S) is about 1mBqm−2. Finally, the dependence of the migration behaviour of 137Cs, 127I and of 129I on the soil properties is discussed. It turns out that there is a distinctly different behaviour of 127I, 129I, and 137Cs in the soils exhibiting different sorption mechanisms for old and recent iodine as well as for 137Cs.

Speciation of 129I in sea, lake and rain waters

Concentrations of the very long-lived fission product 129I and stable iodine (127I) in the Baltic Sea and lake and rain waters from Finland, were measured as well as their occurrence as iodide (I−) and iodate (IO3−). The highest concentrations of both 127I and 129I occurred in sea water, on average 11.1±4.3μg/l and 3.9±4.1×10−9 at/l. In rain and lake waters the concentration of 129I was more or less identical and almost one order of magnitude lower than in sea water. Based on these observations, and data from the literature, it is assumed that the source of 129I in lakes is precipitation and the major source in the Baltic Sea is the inflow of sea water from the North Sea through the Danish Straits. The concentration of 129I in the Baltic Sea has increased by a factor of six during ten years from 1999. In all studied water types the main chemical form of both iodine isotopes was iodide; in sea and lake waters by 92–96% and in rain water by 75–88%. Compared to 127I the fraction of iodide was slightly higher in case of 129I in all waters.