| 1. |
- Aldahan, Ala, et al.
(författare)
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Iodine-129 enrichment in sediment of the Baltic Sea
- 2007
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 22:3, s. 637-647
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Tidskriftsartikel (refereegranskat)abstract
- Sediments are an excellent archive for evaluation of time-series environmental contamination of water systems. Measurements of ultra-trace radioactive species, such as 129I, provide information for both chronologic calibration and anthropogenic emissions during the nuclear era. Here data are presented on 129I and other chemical parameters from two sediment cores collected in the Baltic Sea during 1997. The sediment sections have a relatively uniform grain size (clay–mud) and cover a period of about 50 a. Distribution of 129I in the sediment strongly relates to the liquid release records from the nuclear reprocessing facilities at Sellafield and La Hague. However, syn- and post-depositional alteration of organic matter at the sediment–water interface and within the sediment column may have contributed to slightly obliterating the anthropogenic 129I signals. Indication of Chernobyl-derived 129I occurs in the sediment profile, but is apparently overridden by the overwhelming flux from the nuclear reprocessing facilities. Although the record did not cover the pre-nuclear era (before 1945) sections, the ultra sensitive 129I profile provides a potential tool for relative dating and monitoring sources of water and sediment to the region.
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| 5. |
- Englund, Edvard, et al.
(författare)
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A routine preparation method for AMS measurement of 129I in solid material
- 2007
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 259:1, s. 365-369
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Tidskriftsartikel (refereegranskat)abstract
- Here we present results of an 129I extraction procedure applied to solid matrices (soils and organic matters), which is based on combustion of samples in an oxygen atmosphere. Stepwise heating and continuous warming of the whole system were critical points in order to achieve relatively satisfactory yields of iodine from samples ranging up to 1.5 g. Repeated combustions of blanks show both stable background levels and no significant memory effects. We have processed a series of different types of sample materials including standard soil, maple leaves and surface soil from Uppsala in Central Sweden. The results show analytical reproducibility and agreement with reported values.
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| 7. |
- Englund, Edvard, 1971-
(författare)
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Anthropogenic 129I Traced in Environmental Archives by Accelerator Mass Spectrometry
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Since the beginning of the nuclear era, starting during the 1940s, large amount of radioactivity has been released into the environment. This thesis deals with the temporal and spatial distribution of the anthropogenic radioisotope 129I (T1/2= 15.7 Myr) in northern Europe. A routine sample preparation procedure for extraction of iodine from milligram amounts of solid materials has been developed and aimed for measuring the 129I concentration by the ultra-sensitive accelerator mass spectrometry method. The technique was further used for the analysis of 129I in sediments collected from two lakes in Sweden and one lake in Finland as well as sediments from two sites in the Baltic Sea. In addition, 129I concentrations in aerosol samples from northern and southern Sweden covering the period 1983 to 2000 have been measured. The results reveal a gradual increase in the anthropogenic 129I fluxes since the 1950s that are linked to emissions from the nuclear fuel reprocessing facilities in Sellafield (UK) and La Hague (France). A sharp increase coinciding with the Chernobyl accident is identified from the Swedish lakes located in areas characterised by relatively high Chernobyl fallout. Numerical modeling of the 129I deposition predicts that >50% of the flux to the lake sediments is related to the liquid emissions from the reprocessing facilities. The modeling also reasonably simulates the contribution of the Chernobyl event to the total 129I flux. The novel time series from northern Europe on 129I in aerosols show about one order of magnitude higher concentration in northern compared to southern Sweden. Estimate of 129I dry fallout based on the aerosol data suggests <25% contribution to the total fallout. The distribution of 129I in the sediment archives demonstrates the potential of the isotope as a new time marker for chronological and environmental investigations.
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| 8. |
- Englund, Edvard, et al.
(författare)
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Modeling fallout of anthropogenic I-129
- 2008
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 42:24, s. 9225-9230
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Tidskriftsartikel (refereegranskat)abstract
- Despite the relatively well-recognized emission rates of the anthropogenic 128I, there is little knowledge about the temporal fallout patterns and magnitude of fluxes since the start of the atomic era at the early 1940s.We here present measurements of annual 129I concentrations in sediment archives from Sweden and Finland covering the period 1942-2006. The results revealed impression of 129I emissions from the nuclear reprocessing facility at Sellafield and La Hague and a clear Chernobyl fallout enhancement during 1986. In order to estimate relative contributions from the different sources, a numerical model approach was used taking into accountthe emission rates/ estimated fallout, transport pathways, and the sediment system. The model outcomes suggest a relatively dominating marine source of 129I to north Europe compared to direct gaseous releases. A transfer rate of 129I from sea to atmosphere is derived for pertinent sea areas (English Channel, Irish Sea, and North Sea), which is estimated at 0.04 to 0.21 y-1.
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| 9. |
- Englund, Edvard, et al.
(författare)
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Tracing anthropogenic nuclear activity with I-129 in lake sediment
- 2008
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Ingår i: Journal of Environmental Radioactivity. - : Elsevier BV. - 0265-931X .- 1879-1700. ; 99:2, s. 219-229
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Tidskriftsartikel (refereegranskat)abstract
- This study reports the first data of I-129 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 I-129, a combination of several radionuclides (Pb-210, Cs-137 and C-14) was used to establish an accurate chronology of the sediment profile. The concentration of I-129 exhibits an increasing trend (similar to 10(7) to similar to 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.
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| 10. |
- Englund, Göran, et al.
(författare)
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Long-term variation of link strength in a simple benthic food web
- 2008
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Ingår i: Journal of Animal Ecology. - : British Ecological Society. - 0021-8790 .- 1365-2656. ; 77:5, s. 883-890
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Tidskriftsartikel (refereegranskat)abstract
- 1. The predatory isopod Saduria entomon (L.) and its amphipod prey Monoporeia affinis (Lindström) are key components of the food web in the northern Baltic Sea, together representing 80-90% of the macrobenthic biomass. We use 20 years of stomach content data for Saduria to investigate how diet dynamics affect the stability of the interaction between Saduria and Monoporeia.2. Consumption of the main prey, Monoporeia, fitted a type III functional response. Consumption rates of the most important alternative prey, mysids, were found to be unrelated to mysid densities but negatively related to the density of Monoporeia. The fit of consumption data to a model that assumes passive prey selection was poor. Thus we conclude that some form of active choice is involved.3. The effect of consumption of mysids, the alternative prey, on the stability of this system was investigated using a ‘one predator-two prey' model with stochastic environmental variation. Analysis of the model suggests that feeding on mysids leads to a decreased extinction risk for the predator, Saduria, and reduced density oscillations for both Saduria and its main prey, Monoporeia
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