Wet and dry deposition of 129I in Seville (Spain) measured by accelerator mass spectrometry

The seasonal fluctuations and accumulation of iodine-129 in relation to the hydrogeochemistry of the Wolf Creek Research Basin, a discontinuous permafrost watershed

The long lived radioisotope (129)I is a uranium fission product, and an environmental contaminant of the nuclear age. Consequently, it can trace anthropogenic releases of (129)I in watersheds, and has been identified as a potential means to distinguish water sources in discharge (Nimz, 1998). The purpose of this work was to identify the sources and mass input of (129)I and trace the transport, partitioning and mass balance of (129)I over time in a remote watershed. We monitored (129)I and other geochemical and isotope tracers (e.g. δ(14)CDIC, δ(13)CDIC, δ(2)H, δ(18)O, etc.) in precipitation and discharge from the Wolf Creek Research Basin (WCRB), a discontinuous permafrost watershed in the Yukon Territory, Canada, and evaluated the use of (129)I as a water end-member tracer. Radiocarbon and geochemical tracers of weathering show that discharge is comprised of (i) groundwater baseflow that has recharged under open system conditions, (ii) spring freshet meltwater that has derived solutes through closed-system interaction with saturated soils, and (iii) active layer drainage. The abundance of (129)I and the (129)I/(127)I ratio correlated with geochemical tracers suggests varying contributions of these three water end-members to discharge. The (129)I concentration was highest at the onset of freshet, reaching 17.4×10(6) atoms/L, and likely reflects the lack of interaction between meltwater and organic matter at that time. This peak in (129)I was followed by a decline over the summer to its lowest value. Mass balance calculations of the (129)I budget show that the input to the watershed via precipitation is nearly one order of magnitude higher than the output suggesting that such arctic watersheds accumulate nearly 90% of the annual input, primarily in soil organic matter. Temporal variations in discharge (129)I concentrations correlated with changes in discharge water sources suggesting that (129)I is a promising hydrologic tracer, particularly when used in concert with other stable and radioisotopes.

Time series of 129I and 127I speciation in precipitation from Denmark

Environmental 129I mainly released from reprocessing plants at La Hague (France) and Sellafield (U.K.) provides a unique atmospheric and environmental tracer. This study deals with 129I and 127I speciation in precipitation collected in Denmarkduring 2001-2006 that indicates many newfindings. The concentrations of total 129I in precipitation vary from 0.28 to 5.63 x 10(9) atoms 129I L(-1) with an average of (2.34 +/- 1.43) x 10(9) atoms 129I L(-1), and the annual deposition flux of 129I is (1.25 +/- 0.30) x 10(12) atoms m(-2). Increased 129I levels in precipitation and 129I/ 127I ratio are attributed to the releases of 129I from the reprocessing plants at La Hague and Sellafield. Iodide is the major specie of 129I, which accounts for 50-99% of total 129I. The concentrations of total 127I vary from 0.78 to 2.70 microg iodine L(-1) with an average of 1.63 +/- 0.47 microg iodine L(-1), and annual deposition flux of 0.95 +/- 0.26 mg m(-2). Unlike 129I, iodate is the major specie of 127I, which accounts for 43-93% of total 127I. The 291I/ l27I atomic ratios for total iodine vary from 5.04 to 76.5 x 10(-8) with an average of (30.1 +/- 16.8) x 10(-8). These values are 10 times lower for iodate with an average of (2.95 +/- 3.13) x 10(-8). Seasonal variations of 129I/127 ml values and 129I concentrations are associated with highs in spring and lows in summer-autumn periods. Re-emission of 129 from the surface water of the English Channel, Irish Sea, North Sea, and Norwegian Sea, especially from the European continental coast areas, is evidently the major source of 129I in the precipitation, while stable 127I in the precipitation has multiple sources, i.e., marine, as well as terrestrial emission. This work shows that data on speciation of iodine isotopes can provide thorough indications about the sources and geochemical cycle despite the complicated atmospheric chemistry of iodine.

Tracing anthropogenic nuclear activity with (129)I in lake sediment

This study reports the first data of (129)I fallout in Scandinavia, covering the last 80 years. The investigation is based on sediment sections from a lake in central Sweden. In addition to analysis of (129)I, a combination of several radionuclides ((210)Pb, (137)Cs and (14)C) was used to establish an accurate chronology of the sediment profile. The concentration of (129)I exhibits an increasing trend ( approximately 10(7) to approximately 10(9)atoms/g) during the last 40 years, suggesting a significant atmospheric input from the nuclear reprocessing facilities in Sellafield (UK) and La Hague (France). A peak corresponding to fallout from the Chernobyl accident (1986) is clearly distinguishable, whereas the impact of fallout from the nuclear weapons' tests since the early 1950s is not distinguished.

129I measurements in lake water for an estimate of regional 129I depositions

Estimates of (129)I depositions from (129)I releases of reprocessing plants are so far based on measurements of soil and rain water samples. Because (129)I concentrations in these samples show a highly temporal and spatial variability, the (129)I deposition values deduced from single measurements cannot be seen as representative for a larger area. Here it is proposed to use lake water as an archive for former (129)I depositions, to overcome these limitations. If the limnological parameters of any lake are known, the local (129)I deposition flux can be deduced which is temporally averaged over the flushing time, and spatially averaged over the catchment area of the lake. Samples were collected from various European lakes and from Lake Baikal (Russia). The (129)I concentration in these samples was measured by means of accelerator mass spectrometry, and values between 0.3 and 8.1x10(8) at/l were obtained. Deduced (129)I deposition fluxes averaged over the flushing times of the lakes range from 0.3 to 9.3x10(12) at/m(2) y. The (129)I deposition fluence measured for Lake Baikal is attributed predominantly to releases from the former Soviet reprocessing facilities Chelyabinsk, Tomsk and Krasnoyarsk, while the (129)I deposition fluxes deduced for all other lakes are attributed to releases from the European reprocessing activities at Sellafield, Marcoule and La Hague.

Monitoring iodine-129 in air and milk samples collected near the Hanford Site: an investigation of historical iodine monitoring data

While other research has reported on the concentrations of (129)I in the environment surrounding active nuclear fuel reprocessing facilities, there is a shortage of information regarding how the concentrations change once facilities close. At the Hanford Site, the Plutonium-Uranium Extraction (PUREX) chemical separation plant was operating between 1983 and 1990, during which time (129)I concentrations in air and milk were measured. After the cessation of chemical processing, plant emissions decreased 2.5 orders of magnitude over an 8-year period. An evaluation of (129)I and (127)I concentration data in air and milk spanning the PUREX operation and post-closure period was conducted to compare the changes in environmental levels. Measured concentrations over the monitoring period were below the levels that could result in a potential annual human dose greater than 1 mSv. There was a measurable difference in the measured air concentrations of (129)I at different distances from the source, indicating a distinct Hanford fingerprint. Correlations between stack emissions of (129)I and concentrations in air and milk indicate that atmospheric emissions were the major source of (129)I measured in environmental samples. The measured concentrations during PUREX operations were similar to observations made around a fuel reprocessing plant in Germany. After the PUREX Plant stopped operating, (129)I concentration measurements made upwind of Hanford were similar to the results from Seville, Spain.

The possible contribution of 129I in the drinking water and food supply to the nodular formation of thyroid tissue

Nodular formation of the thyroid tissue can occur as a result of exposure to radiation. The nodular goiter is a common disease seen in the city of Elazig and its surroundings, in the eastern part of Turkey. A prospective study was conducted in an effort to identify the role of 129I in drinking water supply. Specimens obtained from nodular and normal thyroid tissue during surgery and also water specimens were counted by nuclear spectrometric system. 129I radioactivity in nodular tissue was noted to be higher compared to normal tissue and the difference was statistically significant (p <0.05). There was no statistically significant difference (p >0.05) between 129I radioactivity in the water supply and tissue obtained from the patients who have malignant or benign nodular lesions. These results support that the 129I radioactivity level in the water supply is one of the risk factors of the nodular formation of the thyroid tissue in the eastern part of Turkey.

129I and 127I transport in the Mississippi River

The watershed processes which control 129I/127I ratios, 129I and 127I concentrations, and speciation of iodine isotopes were studied through an investigation into the variability of these parameters in the Mississippi River near New Orleans, undertaken in 1996-1998. Analyses of suspended particulate matter (SPM) revealed a greater percent association of 127I than of 129I, resulting in lower 129I/127I ratios in SPM than in surrounding water. Furthermore, crossflow ultrafiltration showed that organo-iodine was the dominant form for both isotopes, with 70-85% of these isotopes found in the 0.45 microm filter-passing fraction associated with colloidal macromolecular organic matter. 129I showed a weak correlation, 127I no correlation, and 129I/127I ratios a strong inverse correlation with river flow rate. Inverse correlations between 129I/127I ratios and river flow rates can be best explained by rainwater and evapotranspiration dominated ratios at base flow and a lowering of the isotope ratios during higher flow due to extra inputs of 127I from soil weathering. We postulate that different equilibration times for 127I and 129I as well as for bomb-produced 129I and reprocessing-produced 129I are responsible for these fractionation effects and the differential mobilities of these isotopes in the Mississippi River watershed.