Thesis for the Degree of Doctor of Philosophy - DTU Orbit

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Iodine Isotopes ( 129 I and 127 I) in the Baltic Proper, Kattegat, and Skagerrak Basins P. YI,* ,† A. ALDAHAN, †,‡ V. HANSEN, § G. POSSNERT, | AND X. L. HOU §,⊥ Department of Earth Sciences, Uppsala University, Uppsala, Sweden, Dpartment of Geology, United Arab Emirates University, Al Ain, UAE, Risø National Laboratory for Sustainable Energy, Technical University of Denmark, Roskilde, Denmark, Tandem Laboratory, Uppsala University, Uppsala Sweden, and Xi’an AMS centre and SKLLQG Institute of Earth Environment, CAS, Xi’an 710075, China Received August 19, 2010. Revised manuscript received December 5, 2010. Accepted December 9, 2010. Radioactive anthropogenic pollution has raised concerns about the present and future environmental status of the semienclosed Baltic Sea. We here study the distribution and inventory of the anthropogenic radioactive 129 I in water depth profiles collected from 16 sites in August 2006 and 19 sites in April 2007 in the Baltic Proper and related Kattegat and Skagerrak basins. The results reveal considerable differences of 129 I concentration in terms of spatial and temporal variability and exposerelativelyhighconcentrationsinthedeepwaters.Variability in the concentration of 127 I, stable natural isotope of iodine, seems to follow changes in the seawater salinity, but in oxygenpoor bottom waters sediment diagenetic release may contribute to the concentration of both isotopes in the water body. Inventory estimates show that 129 I in August 2006 (24.2 ( 15.4 kg) is higher than that in April 2007 (14.4 ( 8.3 kg) within the southern and central Baltic Proper whereas almost a constant load occurs in the Kattegat Basin. Calculated model inventory shows correspondence to empirical data and provides a guideline for future environmental assessment on the impact of 129 I load in the studied region. Introduction The semienclosed Baltic Sea and its ecosystem, surrounded by nine countries and a set of metropolitan areas, greatly affects the economic and recreational situations for more than 80 million people inhabiting its coasts and within its catchment area. However, since the early 1960s, accelerated industrialization and exploitations of natural resources pose a threat to the state of the Baltic Sea environment, such as eutrophication, overfishing, and toxic contaminants. Recent concern over the environmental conditions in the Baltic Sea has derived many governmental agencies and scientists to focus their research on defining the magnitude of the problems and providing suggestions for remedial measures. Among the many pollutants in the Baltic Sea, the anthro- * Corresponding author phone: +46(0)184712584; fax: +46 (0)18 555920; e-mail: peng.yi@geo.uu.se. † Department of Earth Sciences, Uppsala University. ‡ United Arab Emirates University. § Technical University of Denmark. | Tandem Laboratory, Uppsala University. ⊥ Institute of Earth Environment. Environ. Sci. Technol. 2011, 45, 903–909 pogenic concentrations of radioactive 129 I(T1/2 ) 15.7 Myr) were reported to be voluminous and far exceeding natural abundance (1). 129 I concentration in recent environmental samples is 3-8 orders of magnitude higher than prenuclear era level (2). Discharges from the two nuclear fuel reprocessing plants at La Hague (France) and Sellafield (UK) represent the major source contributing to 129 I in the North Sea (1, 3), and the Baltic Sea is largely overwhelmed by this source. Iodine is an essential element for human, as indispensible gradient for the thyroid grand and many tissues normally bound with proteins (4). Thus, systematic and extensive data are necessary in order to understand the level of anthropogenic isotope in natural environment, future changes, and expected environmental hazards. Although a couple of studies raise the awareness, detail samplings that cover the spatial distribution of the isotope in the Baltic Sea are poorly defined. As most of the previous studies were restricted to sporadic samples and surface water (1-3, 5, 6), the distribution patterns and inventory of 129 I in the Baltic Sea have never been systematically estimated. In addition to direct environmental impact, a better understanding of the isotope distribution and sources in the Baltic Sea provide possibility of utilizing the isotopes as an oceanographic tracer (2). Although about 5500 kg have been released to the environment since the atomic era, it is estimated that around 70 000 kg of 129 I is still pending in unprocessed nuclear fuel (7). Such huge amount of 129 I will further address our concerns. As continuous monitoring is time-consuming and expensive, model simulation could instead be a useful tool for future inventory prediction. Another significant aspect of iodine distribution in the marine environmental is that iodine primarily exhibits two main oxidation states as iodide (I - ) and iodate (IO3 - ) and minor organic iodine (8). Given different oxygen condition prevailing in the Baltic Sea, distribution of the iodine isotopes may depend on the extent of changes between oxic and anoxic water. Although iodine is highly soluble chemically, the biophilic nature of iodine tends to enrich the element in the organic fraction (8). Characterized by seasonal variations, the changeable conditions (like quantity of renewed water budget, temperature, organic productivity) in the Baltic Sea may therefore induce relative changes in concentrations of 129 I. To our best knowledge, seasonal monitoring has not been carried out for iodine isotopes. Although the earlier data about iodine (either as 129 Ior 127 I) variability in the Baltic Sea and Skagerrak basin provide some guidelines about the isotopes distribution, there is a lack of systematic depth profile data in term of sampling period and a contemporaneous analysis of both isotopes in the samples. This situation made interpretation of the isotopes, and particular 129 I variability and inventory in water bodies highly speculative and thereby the environmental significance of 129 I and future predictions. Despite the possibility that the isotope may not be a source of immediate environmental hazard, comprehensive understanding of present situation and prediction of future changes are indispensible for the region. We here present extensive data on depth profiles of 129 I and 127 I during two seasons represented by the months of August 2006 and April 2007 in the Baltic Proper and the Skagerrak-Kattegat basin. The data are used, together with other relevant information such oxygen concentration, salinity and temperature, to reveal the magnitude of variability in the iodine isotopes during, early spring (huge influx of fresh water and enhanced thermohaline circulation) and late summer (extensive algal blooming and relatively maxi- 10.1021/es102837p © 2011 American Chemical Society VOL. 45, NO. 3, 2011 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 903 Published on Web 12/29/2010
FIGURE 1. Sampling sites (the red solid circle) for August 2006 and April 2007 expeditions. Blue and turquoise arrows represent 129 I transported from Sellafield and La Hague, respectively. Purple arrows refer to deep flow into the Baltic Proper while red arrows mean surface flow. Ranges of salinity concentration, within the Skagerrak, Kattegat, and Baltic Proper, are labeled. mized stratification). Furthermore, inventory estimates are updated and a model is developed for future prediction, involving the processes of seawater inflow and outflow, freshwater tributary and sedimentation effects. Sampling and Analytical Techniques Depth-profiles of seawaters were collected from 16 sites in August 2006 and 19 sites in April 2007 (Figure 1 and Supporting Information Figure S-1). Sampling was carried out by the research Vessel Argos, operated by the marine division of the Swedish Meteorological and Hydrological Institute. Water samples from different depths were collected in Nansen bottles (Hydro Bios). Meanwhile, a CTD automatic sampler (CTD- model SD204) was launched to measure hydrologic parameters such as salinity, temperature, depth, and dissolved oxygen. Salinity was also measured on board, using an AEG MINISAL 2100 salinometer based on relative conductivity. Oxygen was determined by Winkler titration method using an automated potentiometric titration system and detail of the procedure has been reported elsewhere (9). Iodine isotopes were extracted from seawater by following the method of Hou et al. (10, 11), and the details are presented in the Supporting Information. To all samples, 0.2 mL of 200 Bq/ml 125 I - (NaI) as a chemical yield tracer and 2.0 mg of stable iodine (Woodward Iodine Company, U.S.) as a carrier were used. Iodine species were separated by anion exchange chromatography and determination of 129 I and 127 I were carried out using Pelletron (NEC machine) AMS and an X Series II ICP-MS (Thermal Electron Corporation), under hot plasma conditions, with the Xt interface system. Processing blanks 129 I/ 127 I value was 1.5 ( 0.5 × 10 -13 , which is more than 2 orders of magnitude lower than the value in the samples · . Total analytical uncertainty for 129 I/ 127 I value is normally less than 10% and the detection limit for 127 I, calculated as 3SD of blanks, was 0.27 nM. Results The data sets of 127 I and 129 I together with temperature, oxygen concentration and salinity for the two sampling campaigns 904 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 45, NO. 3, 2011 of August 2006 and April 2007 are presented in Supporting Information Tables S-1 and S-2 and Figures S-2 and S-3. Surface and deep water (above and below halocline, respectively) distributions of the isotopes and their ratio indicate several differences as shown by Figures 2 and 3. In both August 2006 and April 2007, surface water 129 I concentration (Figures 2a and 3a) have their highest values in the Skagerrak basin with a maximum reaching up to 1683 × 10 8 atoms/L (or 106× 10 -8 for 129 I/ 127 I atomic ratio). The trend of concentration decreases toward the Öresund (location 12), and remains rather constant, around 25-36 × 10 8 atoms/ L, in the Baltic Proper. Relatively more variable distribution of 129 I between the two sampling times is revealed by the concentration in the deep water (Figures 2b and 3b). The plume of maxima shown in the Skagerrak during August 2006 is partly retained along the Swedish coasts during April 2007. Relatively high concentrations are also retained throughout the Arkona basin during April, but the more homogeneous distribution in the southern and central parts of the Baltic Proper during April is disturbed by an increase along the Bornholm deep. To summarize the 129 I depth distribution, we observe a 2-19 times decrease in concentration from the surface down to bottom layer in the transition zone between the Kattegat and Skagerrak (locations 17-19, Figure 4). While in the Kattegat (locations 12-16), 129 I concentration gradually increases with depth above halocline, around 35 m, whereas the opposite trend is observed below 35 m. In the Arkona basin (locations 1 and 2, Figures 2a, b and 3a,b), a rather sensitive region for different seasons, high 129 I concentrations are observed in August 2006 in the surface layer, extending to around 30 m, and then the concentration decreases with increasing depth. But an opposite trend was found in April 2007 where 129 I concentration increased from the surface water (33 × 10 8 ( 3 atoms/L) to the bottom water (163 × 10 8 ( 27 atoms/L). In the central Baltic Proper (locations 5-10), there is an obvious 129 I stratified layer where the concentration increases with depth and attains a maximal value 150 × 10 8 atoms/L in the bottom water in August 2006.
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Chemical Speciation Analysis and En
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Thesis for the Degree of Doctor of
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Abstract This thesis deals with che
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environment since they reflect the
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organiske jodformer. Adsorption af
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None of this would have been possib
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Abbreviations and acronyms b+ - pos
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3.1 Analytical Development………
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Table 1 Some properties of iodine P
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In soils/sediments iodine occurs as
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Table 2 Nuclear properties of iodin
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Liquid scintillation counting (LSC)
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The bioavailability of radioactive
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data (Englund et al., 2010; Hou et
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2. Analytical procedures used in th
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2.3 Quantification of total iodine
Page 33 and 34: Fig. 5 Quantification of total iodi
Page 35 and 36: iodate were measured by counting 12
Page 37 and 38: Fig. 6 Sequential extraction proced
Page 39 and 40: a Fig. 8 Calibration curve for (a)
Page 41 and 42: experiment was subjected to combust
Page 43 and 44: Table 7 Adsorption of iodine specie
Page 45 and 46: numbers 11-14), which is about the
Page 47 and 48: marine environment from nuclear fue
Page 49 and 50: 127 I - (ppb) 127 IO3 - (ppb) a b 1
Page 51 and 52: Although the oxygen concentration d
Page 53 and 54: 129 I TBq 2,00E+00 1,80E+00 1,60E+0
Page 55 and 56: • Adsorption of iodine species on
Page 57 and 58: Reference Aldahan A, Kekli A, Possn
Page 59 and 60: Fuge R& Johnson C. 1986. The geoche
Page 61 and 62: Lo´pez-Gutie´rrez JM, Garcı ´a-
Page 63 and 64: Shinohara K. 2004. Measurement and
Page 65 and 66: http://www.irsn.fr/EN/news/Document
Page 67 and 68: Review Analytica Chimica Acta 632 (
Page 69 and 70: Table 1 Nuclear properties and prod
Page 71 and 72: Fig. 2. Liquid discharges of 129 I
Page 73 and 74: Fig. 5. Schematic diagram and pictu
Page 75 and 76: 129 I in iodide and iodate is then
Page 77 and 78: Fig. 8. Diagram of air sampler for
Page 79 and 80: Fig. 10. Iodine L3-edge (a) and K-e
Page 81 and 82: analysis of 129 I in water sample a
Page 83: Yi P, Aldahan A, Hansen V, Possnert
Page 87 and 88: FIGURE 3. Horizontal distribution o
Page 89 and 90: FIGURE 5. Time series data of 129 I
Page 91 and 92: Environmental Science & Technology
Page 93 and 94: prepared using KI and KIO3. No diff
Page 95 and 96: of their contribution to the Baltic
Page 97 and 98: Fig. S-1 Sampling sites (the red so
Page 99 and 100: Fig. S-3 Vertical distribution of I
Page 101 and 102: Fig. S-5 Marine discharges function
Page 103 and 104: Fig.S-7 Relationship between I-129
Page 105 and 106: Table S-1 Results of I-129 and I-12
Page 107 and 108: S17
Page 109 and 110: Paper III Hansen,V., Yi, P., Hou, X
Page 111 and 112: conversion process between iodide a
Page 113 and 114: Table 1 Analytical results of 129 I
Page 115 and 116: August April I-129 iodide ( 10 8 at
Page 117 and 118: References Aldahan A, Kekli A, Poss
Page 119 and 120: Partition of iodine ( 129 I and 127
Page 121 and 122: Norway (Table 1). CTD-casts with ox
Page 123 and 124: 5. Discussion 5.1. Separation of hu
Page 125 and 126: In the present study 40e60% of 129
Page 127 and 128: Hutta, M., Gora, R., 2003. Novel st
Page 129 and 130: Analysis of 129 I and 127 I in arch
Page 131 and 132: et al., 2002). Due to the fact that
Page 133 and 134: espectively. The iodine was leached
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salinities in the same area. Apart
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North Sea. 129 I/ 127 I ratios in w
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Table 2 Analytical results of 129-I
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129 I/ 127 I 1,40E-07 1,20E-07 1,00
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References Aldahan A, Englund E, Po
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O’Dowd, C.; Jimenez, J. L.; Bahre
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Iodine ( 129 I and 127 I) speciatio
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water in winter by molecular oxygen
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0.2 M KNO3. The effluent and the wa
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maximum values is at 0.03-0.06×10
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into the English Channel from the L
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References Aldahan A, Kekli A, Poss
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Risø-PhD-81(EN)
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Thesis for the Degree of Doctor of Philosophy - DTU Orbit

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