Soil and radioactive slurries were analyzed for the presence of beta emitting (241)Pu and (90)Sr. The comparison study between two different LSC apparatus, TriCarb 2200/2550 and Hidex 300 SL, shows ...good agreement for the quench corrected (241)Pu activity concentrations. The (90)Sr activity concentrations of most soil samples were in agreement, and were confirmed by the recommended IAEA-375 value. The Hidex 300 SL is an excellent apparatus to measure pure β-emitters of routine samples.
This study is part of our investigations about the release of persistent organic pollutants from melting Alpine glaciers and the relevance of the glaciers as secondary sources of legacy pollutants. ...Here, we studied the melt-related release of polychlorinated biphenyls (PCBs) in proglacial lakes and glacier streams of the catchment of the Silvretta glacier, located in the Swiss Alps. To explore a spatial and temporal distribution of chemicals in glacier melt, we combined two approaches: (1) analysing a sediment record as an archive of past remobilization and (2) passive water sampling to capture the current release of PCBs during melt period. In addition, we determined PCBs in a non-glacier-fed stream as a reference for the background pollutant level in the area. The PCBs in the sediment core from the Silvretta lake generally complied with trends of PCB emissions into the environment. Elevated concentrations during the most recent ten years, comparable in level with times of the highest atmospheric input, were attributed to accelerated melting of the glacier. This interpretation is supported by the detected PCB fractionation pattern towards heavier, less volatile congeners, and by increased activity concentrations of the radioactive tracer
137
Cs in this part of the sediment core. In contrast, PCB concentrations were not elevated in the stream water, since no significant difference between pollutant concentrations in the glacier-fed and the non-glacier-fed streams was detected. In stream water, no current decrease of the PCBs with distance from the glacier was observed. Thus, according to our data, an influence of PCBs release due to accelerated glacier melt was only detected in the proglacial lake, but not in the other compartments of the Silvretta catchment.
Although ranging among the most expensive gourmet foods, it remains unclear whether Burgundy truffles (Tuber aestivum) accumulate radioactivity at a harmful level comparable to other fungal species. ...Here, we measure the 137Cs in 82 T. aestivum fruit bodies from Switzerland, Germany, France, Italy, and Hungary. All tested specimens reveal insignificant radiocaesium concentrations, thus providing an all-clear for many truffle hunters and cultivators in large parts of Europe as well as the subsequent chain of dealers and customers from around the world. Our results are particularly relevant in the light of ongoing efforts to cultivate Burgundy truffles, as well as the fact that several forest ecosystems are still highly contaminated with 137Cs, for which mushrooms are one of the main pathways to human diets.
Beta-toxin (CPB) is known to be the major virulence factor of
Clostridium perfringens type C strains, which cause necrotizing enteritis in pigs, sheep, goats, calves, and humans. The exact mode of ...action, in particular the cellular targets of CPB in the intestine of naturally affected species, is however still not resolved. To investigate localization of CPB in naturally occurring necrotizing enteritis, we evaluated 52 piglets with spontaneously acquired
C. perfringens type C enteritis and 14 control animals by immunohistochemistry. Our results consistently revealed binding of CPB to vascular endothelial cells in peracute to acute lesions of necrotizing enteritis. Subacute cases, in contrast, demonstrated reduced or no CPB staining at the endothelium, mainly due to widespread vascular necrosis. From these results we conclude, that the pathogenesis of
C. perfringens type C induced necrotizing enteritis involves binding of CPB to endothelial cells in the small intestine during the early phase of the disease. Thus, by targeting endothelial cells, CPB might specifically induce vascular necrosis, hemorrhage and subsequent hypoxic tissue necrosis.
The importance that nitrogen (N) deposition has in driving the carbon (C) sequestration of forests has recently been investigated using both experimental and modeling approaches. Whether increased N ...deposition has positive or negative effects on such ecosystems depends on the status of the N and the duration of the deposition. By combining
δ
13C,
δ
18O,
δ
15N and dendrochronological approaches, we analyzed the impact of two different sources of NO
x
emissions on two tree species, namely: a broadleaved species (
Quercus cerris) that was located close to an oil refinery in Southern Italy, and a coniferous species (
Picea abies) located close to a freeway in Switzerland. Variations in the
c
i/
c
a ratio and the distinction between stomatal and photosynthetic responses to NO
x
emissions in trees were assessed using a conceptual model, which combines
δ
13C and
δ
18O.
δ
15N in leaves, needles and tree rings was found to be a bioindicator of N input from anthropogenic emissions, especially at the oil refinery site. We observed that N fertilization had a stimulatory effect on tree growth near the oil refinery, while the opposite effect was found for trees at the freeway site. Changes in the
c
i/
c
a ratio were mostly related to variations in
δ
13C at the freeway site and, thus, were driven by photosynthesis. At the oil refinery site they were mainly related to stomatal conductance, as assessed using
δ
18O. This study demonstrates that a single method approach does not always provide a complete picture of which physiological traits are more affected by N emissions. The triple isotope approach combined with dendrochronological analyses proved to be a very promising tool for monitoring the ecophysiological responses of trees to long-term N deposition.
We investigated the relationship between the δ13C signal in current-year and 1-year-old needle bulk material, starch extracts, and early- or late-wood in mature spruce trees (Picea abies) to identify ...the modifying influence of climatic conditions on the different δ13C signals. Seasonal patterns of δ13C were determined in total bulk needle material from 1998 to 2000, and in acid soluble starch extracts in 1999 and 2000, and δ13C values of early- and late-wood were measured for the years 1991-2000. δ13C of bulk needle material was most enriched in spring with a trend towards depletion in the course of the season. Current-year needles showed a more distinct seasonal pattern in δ13C compared to 1-year-old needles. Seasonal trends in bulk material and starch were similar, but the highly enriched signal in spring could not be fully explained by the influence of the δ13C values of starch (weighted with the corresponding starch amounts). δ13C of starch in 1-year-old needles, and to a lesser extent of current-year needles, correlated with δ13C of early-wood, indicating a transfer of the isotopic signal. In addition, early-wood δ13C corresponded weakly to winter precipitation. In the summer, δ13C of total bulk needle material and starch showed no relation to the late-wood δ13C signature. Late-wood δ13C, however, related to global radiation, relative humidity and temperature, with more enriched values corresponding to warmer and drier conditions. We conclude that the signature of early-wood is determined more by biochemical fractionation, e.g. during starch formation, than by climatic conditions, which exert only a minor influence and are reflected in the isotopic signal of late-wood.
In multi-species grassland communities, ozone exposure of individual species may differ due to their location inside the canopy. In this study, it was tested how the ozone profile inside a grassland ...canopy is influenced by the vertical distribution of leaf area (LAI) and by meteorological parameters, specifically by the turbulence intensity quantified by the friction velocity (
u
*). Multi-level ozone profiles were measured continuously during the first growth period of intensively managed grassland, and stomatal conductance (
g
s) was measured in the two dominant species, i.e. white clover (
Trifolium repens) at 0.25
m and meadow foxtail (
Alopecurus pratensis) at 0.50
m. In the two-layer structure of the canopy, with <20% of LAI located in the upper half, radiation (PAR) was only moderately reduced throughout the canopy thus favouring high
g
s also in the lower part. Daytime ozone concentration at 0.25
m, where white clover was dominant, was reduced on average by 36% of the value at the reference height of 0.90
m. When scaled with canopy height, this reduction was considerably larger than most comparable published data for other vegetation types. The shape of the ozone profile in the canopy was not affected by increasing LAI from 4.7 to 6.8
m
2
m
−2 or by the changing vertical distribution of LAI during the observation period. The main environmental influence on the shape of the profile could be attributed to
u
*. Generally, relative in-canopy concentrations of ozone increased with
u
*. This could explain the stronger and more variable ozone depletion during nighttimes. The different levels of ozone exposure of species predominantly located in the upper and lower parts of the canopy supports a multi-layer approach to modelling uptake of ozone, which is important for the assessment of ozone risks for individual plants growing in grasslands.
The separation methods for soil samples applied at PSI are based on extraction chromatography and ion exchange. After sample leaching, the actinides are pre-concentrated via precipitation using ...oxalic acid. Besides the classical separation methods applying the extraction chromatographic resins U/TEVA™ (for U, Th), TRU™ (Pu, Am), new methods were recently implemented to increase the radiochemical recovery of particularly trivalent Am and Cm. These methods do not require initial reduction of Pu(IV) to Pu(III) but stabilize Pu on the tetravalent oxidation state using a mixture of NaNO
2/H
2O
2 in strong acidic medium. The Pu-fraction is then fixed along with Th onto Dowex AG 1-X2 anion exchanger resin. Th is eluted via complexation with 10
M HCl, Pu via reduction with HI. The fractions of Am+Cm and U are loaded onto DGA™ resin. This resin shows extraordinary high distribution coefficients (
k′-values) exceeding 10
4 (for Am) in strong nitric acid medium. The separation between U and Am is obtained quantitatively by decreasing the HNO
3 concentration from 3 to 0.25
M (stripping of the U-fraction) while Am can be easily eluted thereafter using 0.25
M HCl as complexation compound.
241Pu was determined in slurry samples from a nuclear reactor decommissioning project at the Paul Scherrer Institute (Switzerland). To validate the results, the
241Pu activities of five samples were ...determined by LSC (TriCarb and Quantulus) and ICP-MS, with each instrument at a different laboratory. In lack of certified reference materials for
241Pu, the methods were further validated using the
241Pu information values of two reference sediments (IAEA-300 and IAEA-384). Excellent agreement with the results was found between LSC and ICP-MS in the nuclear waste slurries and the reference sediments.
► Good agreement between the
241Pu activity of 5 slurry samples, using 3 measurement techniques. ►
241Pu information values of two IAEA samples agreed well for the 3 measurement techniques. ► Low detection limits were achieved; 1.8
Bq/kg (Quantulus), 2
Bq/kg (ICP-MS) and 3.5
Bq/kg (TriCarb).
Radioactive waste (slurry) from a detention pond deriving from two research reactors and several inactive and active drain outlets at the Paul Scherrer Institute are the basis for the current
90Sr ...investigation. For decomposition, a microwave method was applied, where 1
g of dry-ashed slurry was partially dissolved (HNO
3 (65%)/H
2O
2 (30%); v:v=8:2). In this slurry we obtained an
90Sr activity of 5.3±0.2
Bq/g in solution. In a second run, we applied a borate-fusion (Li metaborate/Li tetraborate (80:20
w/w%) dissolving 1
g of dry-ashed “Si-free” slurry at 1100
°C in a muffle furnace. We achieved an
90Sr activity of (7.8±0.3)
Bq/g, yet observing BaSO
4 precipitation during the chromatographical separation of Sr. An alkali fusion using Na
2CO
3 was done using the Bunsen burner and the muffle furnace for 20
min at 1000
°C, in combination. During formation of the hot glass, the surplus of Na
2CO
3, produced Na
2SO
4 and BaCO
3 in solid form. The hot glass was dissolved in deionised water, removing thus the SO
4
2− ions. Dissolving the residue directly in HNO
3, solves Ba as Ba(NO
3)
2 and thus we achieved over 80% of the
133Ba activity in the solution, as measured by γ-spectrometry.
85Sr tracer of 88.0%±3.3% was recovered, yielding on average in (7.4±0.3)
Bq/g of
90Sr activity. The increase of 2.1–2.5
Bq/g of
90Sr activity achieved with the alkali fusion, and the Li metaborate/Li tetraborate 80:20
w/w% fusion, respectively, clearly shows that some Sr must have been present as SrSO
4 in the slurry.
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