Os radionuclídeos artificiais e naturais podem ser comumente encontrados em diversos compartimentos da crosta terrestre. Algumas espécies de cogumelos têm uma alta capacidade em absorver radionuclídeos e elementos tóxicos vindos do solo. A dieta alimentar destaca-se como uma das principais vias de contaminação radioativa. Portanto, a medida da radioatividade no ambiente e em alimentos é extremamente importante para monitorar os níveis de radiação aos quais o homem possa estar exposto de forma direta ou indireta. A biomonitoração ambiental tem demonstrado que diversos organismos como os crustáceos, peixes e cogumelos são usados para avaliar a contaminação e a qualidade dos ecosssistemas. Existem vários radionuclídeos que podem ser acumulados por cogumelos, incluindo 40 K, 137Cs, 232Th e 238U. No entanto há poucos estudos em países do hemisfério Sul, sobre os níveis de radioatividade natural e artificial em cogumelos. Este trabalho consistiu na determinação das atividades específicas de elementos radioativos naturais e 137Cs em cogumelos comestíveis comercializados em São Paulo-Brasil. As amostras de cogumelos comestíveis foram adquiridas em diferentes pontos comerciais da cidade de São Paulo, especialmente em mercados municipais, porém algumas foram adquiridas diretamente de produtores de algumas regiões como Mogi das Cruzes, Mirandópolis, Suzano e Juquitiba. Cerca de 400 g de cada espécie de cogumelos comestíveis foram coletadas, incluindo Agaricus sp, Lentinula sp e Pleurotus sp. Todas as amostras foram preparadas e acondicionadas em recipientes de polietileno, seladas e armazenadas por aproximadamente 35 dias, para que fosse estabelecido o equilíbrio radioativo secular, antes que se iniciassem as contagens. As atividades gama do 40K, 137Cs, 232Th e 238U foram medidas por espectrometria gama. O equipamento utilizado consistiu de um detector de Germânio Hiperpuro conectado a um sistema eletrônico. As medidas foram de aproximadamente 200000 segundos. A eficiência do detector foi medida utilizando os materiais de referência: IAEA-300, IAEA-327 e IAEA-375. Os resultados obtidos para as amostras de cogumelos comestíveis variaram de 461 a 1535 Bq kg 1, 1,4 a 10,6 Bq kg 1, 6,2 a 54,2 Bq kg 1 e 14 a 66 Bq kg 1 em peso seco, para 40K,137Cs, 232Th e 238U, respectivamente. Os níveis de 137Cs estão de acordo com o fallout radioativo do hemisfério Sul, apresentando concentrações abaixo dos níveis máximos estabelecidos pela CNEN. Comparando os resultados obtidos com outros trabalhos da literatura, comprovou-se que os valores das atividades encontradas para os radionuclíddeos naturais estão dentro dos níveis normais de radioatividade para este produto. As espécies de cogumelos analisadas podem ser consumidas sem riscos de contaminação. O método de análise empregado neste estudo demonstrou-se adequado para estimar a atividade 232Th e 238U e determinar as atividades de 40K e 137Cs, em amostras biológicas. Este estudo assinala a primeira vez em que cogumelos comestíveis, no Brasil foram estudados para avaliar o conteúdo radioativo e, como tal, é uma contribuição para investigações futuras nesta área. / Artificial and natural radionuclides are commonly found in several compartments of the earth\'s crust. Some mushroom species have a high capacity to absorb radionuclides and toxic elements from the soil. Diet is considered as one of the main routes of radioactive contamination. Therefore, radioactivity measurements in the environment and in food are extremely important to monitor the radiation levels that human can be exposed to either directly or indirectly. Environmental biomonitoring has demonstrated that diverse organisms such as crustaceans, fish and mushrooms are useful when evaluating both the contamination and the quality of the ecosystems. There are actually several radionuclides that can be accumulated in mushrooms, including 40 K, 137Cs, 232Th and 238U. There are few studies in the Southern hemisphere countries, on the natural and artificial radioactivity levels in mushrooms. The present study evaluated 40K, 137Cs, 232Th and 238U in commercialized edible mushrooms in the state of São Paulo, Brazil. The edible mushroom samples were acquired in different commercial establishments in the São Paulo metropolitan region, specifically in Municipal Markets. Some samples were acquired directly from producers located in the cities of Mogi das Cruzes, Mirandópolis, Suzano and Juquitiba. About 400g were colleted for each edible mushroom species, which included Agaricus sp, Pleurotus sp and Lentinula sp species. All the samples were prepared and stored in polyethylene bottles for approximately 35 days, so that secular equilibrium could be established before counting. The 40K, 137Cs, 232Th and 238U gamma activities were measured by gamma spectrometry. The equipment consisted of a Hiperpure Germanium detector connected to an electronic system. The detector efficiency was obtained from measurements of reference materials: IAEA-300, IAEA-327 and IAEA-375. The results for the specific activities in edible mushrooms samples ranged from 461 to 1535 Bq kg1, 1.4 to 10.6 Bq kg1, 6.2 to 54.2 Bq kg1 and 14 to 66 Bq kg1 d.w., for 40K,137Cs, 232Th e 238U, respectively. The 137Cs levels are in accordance with the Southern hemisphere radioactive fallout, the concentrations are below the maximum levels established by CNEN. Comparing the result values with these found in published literature, the values of the activities found for natural radionuclides are within the normal radioactivity levels for this kind of food. Hence, the studied mushroom species can be consumed without risk of contamination. The employed methodology in this study showed adequate to estimate 232Th and 238U specific activities and to determine 40K and 137Cs activities in biological samples. This study marks the first time that edible mushrooms in Brazil have been studied to evaluate their radioactivity contents and as such is a contribution for future research in this area.

Os radionuclídeos artificiais e naturais podem ser comumente encontrados em diversos compartimentos da crosta terrestre. Algumas espécies de cogumelos têm uma alta capacidade em absorver radionuclídeos e elementos tóxicos vindos do solo. A dieta alimentar destaca-se como uma das principais vias de contaminação radioativa. Portanto, a medida da radioatividade no ambiente e em alimentos é extremamente importante para monitorar os níveis de radiação aos quais o homem possa estar exposto de forma direta ou indireta. A biomonitoração ambiental tem demonstrado que diversos organismos como os crustáceos, peixes e cogumelos são usados para avaliar a contaminação e a qualidade dos ecosssistemas. Existem vários radionuclídeos que podem ser acumulados por cogumelos, incluindo 40 K, 137Cs, 232Th e 238U. No entanto há poucos estudos em países do hemisfério Sul, sobre os níveis de radioatividade natural e artificial em cogumelos. Este trabalho consistiu na determinação das atividades específicas de elementos radioativos naturais e 137Cs em cogumelos comestíveis comercializados em São Paulo-Brasil. As amostras de cogumelos comestíveis foram adquiridas em diferentes pontos comerciais da cidade de São Paulo, especialmente em mercados municipais, porém algumas foram adquiridas diretamente de produtores de algumas regiões como Mogi das Cruzes, Mirandópolis, Suzano e Juquitiba. Cerca de 400 g de cada espécie de cogumelos comestíveis foram coletadas, incluindo Agaricus sp, Lentinula sp e Pleurotus sp. Todas as amostras foram preparadas e acondicionadas em recipientes de polietileno, seladas e armazenadas por aproximadamente 35 dias, para que fosse estabelecido o equilíbrio radioativo secular, antes que se iniciassem as contagens. As atividades gama do 40K, 137Cs, 232Th e 238U foram medidas por espectrometria gama. O equipamento utilizado consistiu de um detector de Germânio Hiperpuro conectado a um sistema eletrônico. As medidas foram de aproximadamente 200000 segundos. A eficiência do detector foi medida utilizando os materiais de referência: IAEA-300, IAEA-327 e IAEA-375. Os resultados obtidos para as amostras de cogumelos comestíveis variaram de 461 a 1535 Bq kg 1, 1,4 a 10,6 Bq kg 1, 6,2 a 54,2 Bq kg 1 e 14 a 66 Bq kg 1 em peso seco, para 40K,137Cs, 232Th e 238U, respectivamente. Os níveis de 137Cs estão de acordo com o fallout radioativo do hemisfério Sul, apresentando concentrações abaixo dos níveis máximos estabelecidos pela CNEN. Comparando os resultados obtidos com outros trabalhos da literatura, comprovou-se que os valores das atividades encontradas para os radionuclíddeos naturais estão dentro dos níveis normais de radioatividade para este produto. As espécies de cogumelos analisadas podem ser consumidas sem riscos de contaminação. O método de análise empregado neste estudo demonstrou-se adequado para estimar a atividade 232Th e 238U e determinar as atividades de 40K e 137Cs, em amostras biológicas. Este estudo assinala a primeira vez em que cogumelos comestíveis, no Brasil foram estudados para avaliar o conteúdo radioativo e, como tal, é uma contribuição para investigações futuras nesta área. / Artificial and natural radionuclides are commonly found in several compartments of the earth\'s crust. Some mushroom species have a high capacity to absorb radionuclides and toxic elements from the soil. Diet is considered as one of the main routes of radioactive contamination. Therefore, radioactivity measurements in the environment and in food are extremely important to monitor the radiation levels that human can be exposed to either directly or indirectly. Environmental biomonitoring has demonstrated that diverse organisms such as crustaceans, fish and mushrooms are useful when evaluating both the contamination and the quality of the ecosystems. There are actually several radionuclides that can be accumulated in mushrooms, including 40 K, 137Cs, 232Th and 238U. There are few studies in the Southern hemisphere countries, on the natural and artificial radioactivity levels in mushrooms. The present study evaluated 40K, 137Cs, 232Th and 238U in commercialized edible mushrooms in the state of São Paulo, Brazil. The edible mushroom samples were acquired in different commercial establishments in the São Paulo metropolitan region, specifically in Municipal Markets. Some samples were acquired directly from producers located in the cities of Mogi das Cruzes, Mirandópolis, Suzano and Juquitiba. About 400g were colleted for each edible mushroom species, which included Agaricus sp, Pleurotus sp and Lentinula sp species. All the samples were prepared and stored in polyethylene bottles for approximately 35 days, so that secular equilibrium could be established before counting. The 40K, 137Cs, 232Th and 238U gamma activities were measured by gamma spectrometry. The equipment consisted of a Hiperpure Germanium detector connected to an electronic system. The detector efficiency was obtained from measurements of reference materials: IAEA-300, IAEA-327 and IAEA-375. The results for the specific activities in edible mushrooms samples ranged from 461 to 1535 Bq kg1, 1.4 to 10.6 Bq kg1, 6.2 to 54.2 Bq kg1 and 14 to 66 Bq kg1 d.w., for 40K,137Cs, 232Th e 238U, respectively. The 137Cs levels are in accordance with the Southern hemisphere radioactive fallout, the concentrations are below the maximum levels established by CNEN. Comparing the result values with these found in published literature, the values of the activities found for natural radionuclides are within the normal radioactivity levels for this kind of food. Hence, the studied mushroom species can be consumed without risk of contamination. The employed methodology in this study showed adequate to estimate 232Th and 238U specific activities and to determine 40K and 137Cs activities in biological samples. This study marks the first time that edible mushrooms in Brazil have been studied to evaluate their radioactivity contents and as such is a contribution for future research in this area.

In case of a release of radioactive nuclides into the environment it is necessary to  have reliable methods to estimate the potential effect on people and the ecosystem. In this context the total activity deposited, the elemental composition and the depth distribution are of importance. An efficient in situ method to estimate the average contamination over larger areas using high purity germanium (HPGe) detectors has been developed. The method combines simulation of photon transport with measured detector properties. The total activity of 137Cs determined from gamma-ray spectra recorded in situ are compared to results from soil sampling. Another in situ method has been developed to determine the depth distribution of a radionuclide contamination, using an array of small detectors inserted into the ground, as an alternative to the standard procedure of soil sampling. The possibility to use cadmium telluride (CdTe) detectors as well as lanthanum bromide (LaBr3) detectors has been investigated. As a demonstration of the developed method the small-scale variation of the activity distributions in an area covering 350 m2 have been measured and is compared to results obtained by other methods. / At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted.

Das künstliche Radionuklid 137Cs wurde seit über einem halben Jahrhundert in die Natur eingebracht. Sein erstes Erscheinen in Sedimenten der zentraleuropäischen Seen korrespondiert mit den Nuklearwaffentests in den 60er-Jahren des 20. Jahrhunderts. Die stärkste Kontaminierung der europäischen Seen und Flüsse entstand als Folge des radioaktiven Niederschlags nach dem Unfall in Tschernobyl im Frühjahr 1986. In dieser Arbeit wurde das Migrationsverhalten des künstlichen 137Cs im Lago Maggiore und anderen Seen im Alpenvorland als Folge dieses Niederschlags untersucht. Der Lago Maggiore zählt zu den größten Trinkwasserreservoiren südlich der Alpen. Nach dem Unfall in Tschernobyl gingen ungefähr 20 kBq•m-2 des 137Cs auf die Oberfläche des Sees nieder. Im Zeitraum von 2003 bis 2005 wurden Sedimentkerne und Wasserproben an sieben unterschiedlichen Stellen des Lago Maggiore entnommen. Diese Arbeit beschäftigt sich mit Daten über die Verteilung des 137Cs in den Zuflüssen, dem Wasser des Sees, in Schwebstoffen und Bodensedimenten und mit der Assoziierung von 137Cs mit verschiedenen geochemischen Fraktionen. Um den Abfluss des 137Cs aus dem Wassereinzugsgebiet in den Fluss zu modellieren, wurde ein Compartmentmodell verwendet. Zur Modellierung der Aufnahmemenge von 137Cs im Sediment und der vertikalen Verteilung innerhalb dessen wurde ein Diffusions-Konvektions-Modell entwickelt. Dieses Modell berücksichtigt die Aufnahme von Aktivität durch Sedimentation, Fixierung und Rücklösung, retardierte Diffusion, die Verdichtung des Sediments sowie den Einfluss konkurrierender Ionen auf die retardierte Diffusion innerhalb des Sediments. Die Ergebnisse der Parameteroptimierung – im Wesentlichen die Sedimentationsrate und der 137Cs-Verteilungskoeffizient Kd, welcher die Aufnahme der Aktivität in das Sediment determiniert – werden erörtert und mit denen anderer europäischer Seen, die eine ähnliche 137Cs-Deposition, aber unterschiedliche limnologische Eigenschaften aufweisen, verglichen. Zur Beurteilung der Bioverfügbarkeit von 137Cs wurde die 137Cs-Aktivitätskonzentrationen von Fischproben aus dem Lago Maggiore gemessen. Aus bereits existierenden Daten und unseren Messergebnissen wurden 137Cs Fisch-Wasser Konzentrations-Verhältnisse errechnet und mit denen für andere Seen, die von ähnlichen 137Cs-Kontaminationen betroffen sind, verglichen. / Artificial Cs-137 has been introduced into the environment for more than half a century. Its first appearance in central European lake sediments corresponds to the nuclear weapons testing in the 1960s. The largest contamination of European lakes and rivers occurred as a consequence of the fallout after the Chernobyl accident in spring 1986. In this work the migration behaviour of artificial Cs-137 in Lago Maggiore and other pre-alpine lakes as a consequence of these fallouts was studied. Lago Maggiore is one of the largest drinking water reservoirs in the south of the Alps. After the Chernobyl accident roughly 20 kBq•m-2 of 137Cs were deposited onto the lake surface. From 2003 to 2005 bottom sediment cores and water samples were collected at 7 different locations of Lago Maggiore. Data on the 137Cs distribution in tributaries, lake water, suspended matter, bottom sediments, and the 137Cs association to different geochemical fractions are presented in this work. To model the run-off of 137Cs from the watershed into the lake a compartment model was used. For modeling the input of 137Cs into and the vertical distribution within the sediment a diffusion–convection type model was developed. This model takes into account the uptake of activity by sedimentation, fixation and redissolution, retarded diffusion, the influence of competing ions on the retarded diffusion within the sediments, and compaction of sediments. The results of the parameter optimization – mainly the sedimentation rate and the 137Cs distribution coefficient Kd, which determines the uptake of activity into the sediment – are discussed and compared with those of other European lakes characterized by similar 137Cs deposition levels but different limnological properties. To estimate the bioavailability of 137Cs, its activity concentrations in fish samples from Lago Maggiore were measured. Combining the existing data with our measurements, 137Cs fish–water concentration ratios were calculated and compared with those for other lakes which were affected by similar 137Cs contamination.

Das künstliche Radionuklid 137Cs wurde seit über einem halben Jahrhundert in die Natur eingebracht. Sein erstes Erscheinen in Sedimenten der zentraleuropäischen Seen korrespondiert mit den Nuklearwaffentests in den 60er-Jahren des 20. Jahrhunderts. Die stärkste Kontaminierung der europäischen Seen und Flüsse entstand als Folge des radioaktiven Niederschlags nach dem Unfall in Tschernobyl im Frühjahr 1986. In dieser Arbeit wurde das Migrationsverhalten des künstlichen 137Cs im Lago Maggiore und anderen Seen im Alpenvorland als Folge dieses Niederschlags untersucht. Der Lago Maggiore zählt zu den größten Trinkwasserreservoiren südlich der Alpen. Nach dem Unfall in Tschernobyl gingen ungefähr 20 kBq•m-2 des 137Cs auf die Oberfläche des Sees nieder. Im Zeitraum von 2003 bis 2005 wurden Sedimentkerne und Wasserproben an sieben unterschiedlichen Stellen des Lago Maggiore entnommen. Diese Arbeit beschäftigt sich mit Daten über die Verteilung des 137Cs in den Zuflüssen, dem Wasser des Sees, in Schwebstoffen und Bodensedimenten und mit der Assoziierung von 137Cs mit verschiedenen geochemischen Fraktionen. Um den Abfluss des 137Cs aus dem Wassereinzugsgebiet in den Fluss zu modellieren, wurde ein Compartmentmodell verwendet. Zur Modellierung der Aufnahmemenge von 137Cs im Sediment und der vertikalen Verteilung innerhalb dessen wurde ein Diffusions-Konvektions-Modell entwickelt. Dieses Modell berücksichtigt die Aufnahme von Aktivität durch Sedimentation, Fixierung und Rücklösung, retardierte Diffusion, die Verdichtung des Sediments sowie den Einfluss konkurrierender Ionen auf die retardierte Diffusion innerhalb des Sediments. Die Ergebnisse der Parameteroptimierung – im Wesentlichen die Sedimentationsrate und der 137Cs-Verteilungskoeffizient Kd, welcher die Aufnahme der Aktivität in das Sediment determiniert – werden erörtert und mit denen anderer europäischer Seen, die eine ähnliche 137Cs-Deposition, aber unterschiedliche limnologische Eigenschaften aufweisen, verglichen. Zur Beurteilung der Bioverfügbarkeit von 137Cs wurde die 137Cs-Aktivitätskonzentrationen von Fischproben aus dem Lago Maggiore gemessen. Aus bereits existierenden Daten und unseren Messergebnissen wurden 137Cs Fisch-Wasser Konzentrations-Verhältnisse errechnet und mit denen für andere Seen, die von ähnlichen 137Cs-Kontaminationen betroffen sind, verglichen. / Artificial Cs-137 has been introduced into the environment for more than half a century. Its first appearance in central European lake sediments corresponds to the nuclear weapons testing in the 1960s. The largest contamination of European lakes and rivers occurred as a consequence of the fallout after the Chernobyl accident in spring 1986. In this work the migration behaviour of artificial Cs-137 in Lago Maggiore and other pre-alpine lakes as a consequence of these fallouts was studied. Lago Maggiore is one of the largest drinking water reservoirs in the south of the Alps. After the Chernobyl accident roughly 20 kBq•m-2 of 137Cs were deposited onto the lake surface. From 2003 to 2005 bottom sediment cores and water samples were collected at 7 different locations of Lago Maggiore. Data on the 137Cs distribution in tributaries, lake water, suspended matter, bottom sediments, and the 137Cs association to different geochemical fractions are presented in this work. To model the run-off of 137Cs from the watershed into the lake a compartment model was used. For modeling the input of 137Cs into and the vertical distribution within the sediment a diffusion–convection type model was developed. This model takes into account the uptake of activity by sedimentation, fixation and redissolution, retarded diffusion, the influence of competing ions on the retarded diffusion within the sediments, and compaction of sediments. The results of the parameter optimization – mainly the sedimentation rate and the 137Cs distribution coefficient Kd, which determines the uptake of activity into the sediment – are discussed and compared with those of other European lakes characterized by similar 137Cs deposition levels but different limnological properties. To estimate the bioavailability of 137Cs, its activity concentrations in fish samples from Lago Maggiore were measured. Combining the existing data with our measurements, 137Cs fish–water concentration ratios were calculated and compared with those for other lakes which were affected by similar 137Cs contamination.

<p>Ensåsengruvan is a mine situated within Ljusdals municipality in central Sweden. Themine was in use from 1984 to 1991 and has since been undergoing a remediation program. Mine tailings from sulfide rich ore is a potential environmental hazard due to its tendency to cause acid waters and heavy metal leakage. Lake Ensjön is situated one kilometer from the mine area. Due to the hydrological conditions it was not expected to receive inflowing water from the mining area. A study done in 2005 showed high amounts of heavy metals in the lake.</p><p>In this study water and sediments was analyzed to confirm the results from the 2005 study. Water was sampled two times during summer 2006 from the lake and adjoining streams. Sediment samples were collected with a core sampler at ten different locations within the lake. The water and sediment samples were analyzed for heavy metal content. Sub-samples from different depths in the sediment core were extracted so that conclusions on the contamination history could be drawn. The sediments were dated trough Cs-137 analyses. The depth in the profile with the highest Cs-137 content can be dated to the time of the Chernobyl fallout (1986). After dating, relevant samples were analyzed for metal content.</p><p>The results show that Ensjön is contaminated by a local source. The surface sediments are high in copper, zinc, nickel and cadmium content. The content is high both compared to the samples from deeper in the sediment core and the surface sediments analyzed in the reference study done in 1980. The amounts of heavy metals are also high relative to the standards set by the Swedish Environmental Protection Agency. The water from the stream adjoining the lake from the mining area is high in content of the previously mentioned metals. The methods used, including sediment dating and metal analyses together with water analyses, has proven to be useful in investigating a suspected contamination from a point source.</p><p>It can be concluded that Lake Ensjön is contaminated with water from the mine waste. No other sources in the catchment area can be the source of the enriched amounts of heavy metals. Focus should in further work be put upon finding the exact source of leakage from the mining area.</p> / <p>Från Enåsengruvan i Ljusdals kommun utvanns ur sulfidmalm guld, silver och koppar under åren 1984 till 1991. Avfall från sulfidmalmsgruvor medför miljöproblem genom försurning och läckage av tungmetaller. Vanligtvis täcks avfallet med jordmassor eller vatten för att förhindra påverkan på naturen. De studier som genomfördes under prospekteringen visade på att Ensjön, som är belägen inom en kilometers avstånd från gruvområdet, inte skulle påverkas av gruvan men en provtagning under 2005 visade på höga halter av tungmetaller i sjön.</p><p>I denna studie har Ensjöns vattenkvalitet undersökts genom vatten och sedimentanalyser. Vattenprover i sjön och dess inlopp togs två gånger under sommaren 2006 och sedimentprover togs vid ett tillfälle på tio olika lokaler i sjön. En djupprofil av sedimenten analyserades för att föroreningshistoriken från innan gruvan togs i bruk till nutid skulle kunna kartläggas. För att datera sedimenten analyserades de med avseende på Cs-137. De högsta halterna av Cs-137 kan härledas till nedfallet från Tjernobylolyckan 1986. Efter datering valdes lämpliga prover ut för metallanalys.</p><p>Resultaten visar på förhöjda halter av koppar, zink, nickel och kadmium. Halterna i ytsedimenten är höga både jämfört med de halter som återfinns på större djup i sedimentprofilen, motsvarande avsättning innan gruvdriften och vad som uppmättes i referensstudien från 1980. Halterna är även höga relativt de jämförvärden som Naturvårdsverket satt upp. Vattenanalyserna visar på att vattnet i inflödet från gruvområdet innehåller höga halter av de tidigare nämnda metallerna. Metoden med Cs-137-datering och analys med avseende på metaller av sediment har visat sig fungera väl för kartläggning av en nutida förorening från en punktkälla. Tillsammans med kompletterande vattenprover ger det en bra bild av den rådande situationen.</p><p>Då resultaten visar att Ensjöns vatten är påverkat av en punktkälla och alla andra källor kan uteslutas får det anses klarlagt att sjöns vatten är påverkat av dränagevatten från gruvområdet. Fortsatta studier bör fokusera på att klarlägga den exakta källan till läckaget från gruvområdet.</p>

Sr-90 and Cs-137 are two key fission products that are important in a number of radioactive waste or contamination clean-up scenarios. This thesis investigates the sorptiondesorption behaviour of these two radionuclides with a number of sorbents relevant to one of the legacy waste storage ponds on the Sellafield site. Sorption-desorption studies were undertaken on brucite (Mg(OH)2), UO2 and UO3 powders to represent components of the fine particulate sludge that has accumulated on the bottom of the pond, resulting from corrosion of the Magnox fuel elements. Brucite was found not to have a significant interaction with Sr-90 or Cs-137. However, organic molecules in the form of humic acid and Pseudanabaena catenata cyanobacterial growth supernatant were both found to enhance sorption interactions of Sr-90 with brucite. The effect of humic acid was pH dependent and appeared to control both sorption and desorption behaviour at pH 11.5. Uranium oxides had the most significant effect on controlling Sr-90 and Cs-137 sorption-desorption behaviour. In this work X-Ray Absorption Spectroscopy (XAS) showed that 90Sr sorbed strongly to both uranium oxides as a bidentate inner-sphere complex. Humic acid did not appear to alter the interaction of Sr-90 with UO2. For Cs-137 there was a significant, reversible interaction with both oxides, although the interaction was far stronger with UO3. Successful detection of stable Sr and Cs isotopes on uranium oxides was achieved with Laser Induced Breakdown Spectroscopy (LIBS).

<p>This thesis deals with the atmospheric distribution of the cosmogenic isotopes ⁷Be (half-life 53 days) and ¹⁰Be (half-life 1.51 million years) as well as the anthropogenic isotope ¹³⁷Cs (half-life 30 years) in aerosols and precipitation. Samples covering continuous or selected parts of the period 1972-2005 in Sweden and Europe are evaluated with respect to production, air mass transport and fallout processes. Such information is valuable in assessing the potential of these isotopes as indicators of air mass mixing and solar modulation factors that affect climate change. The results of ⁷Be and ¹⁰Be show seasonal variability and an 11-year cyclic pattern which is anti-correlated with the solar activity. Variations in seasonal trends of ⁷Be and ¹³⁷Cs in aerosols during the post- and pre-Chernobyl period reflect tropospheric influence from ¹³⁷Cs-heavily contaminated regions. A clear latitude dependence is observed in our beryllium isotope data where highest fallout is found in mid-latitudes compared to high and low latitude regions in the Northern hemisphere. This pattern reflects the general air mass circulation in the troposphere. However, stratospheric air mass influence was also identified in mainly single events and through tropopause folding during spring-summer seasons. The ratio of ¹⁰Be/⁷Be is used to estimate effects of air mass transport on production signal. The results show ratios between 1 and 3, much higher than the theoretically predicted value (0.6) in the atmosphere, which suggests contribution from ⁷Be-depleted (old) air masses. The relationship between monthly ⁷Be atmospheric activity and Total Fractional Cloud Cover (TFCC), collected from satellite imagery, over Sweden for the years (1991-2000) indicates a negative seasonal correlation. This observation can be related to depletion of aerosol from the atmosphere due to trapping in clouds. </p>

This thesis deals with the atmospheric distribution of the cosmogenic isotopes 7Be (half-life 53 days) and 10Be (half-life 1.51 million years) as well as the anthropogenic isotope 137Cs (half-life 30 years) in aerosols and precipitation. Samples covering continuous or selected parts of the period 1972-2005 in Sweden and Europe are evaluated with respect to production, air mass transport and fallout processes. Such information is valuable in assessing the potential of these isotopes as indicators of air mass mixing and solar modulation factors that affect climate change. The results of 7Be and 10Be show seasonal variability and an 11-year cyclic pattern which is anti-correlated with the solar activity. Variations in seasonal trends of 7Be and 137Cs in aerosols during the post- and pre-Chernobyl period reflect tropospheric influence from 137Cs-heavily contaminated regions. A clear latitude dependence is observed in our beryllium isotope data where highest fallout is found in mid-latitudes compared to high and low latitude regions in the Northern hemisphere. This pattern reflects the general air mass circulation in the troposphere. However, stratospheric air mass influence was also identified in mainly single events and through tropopause folding during spring-summer seasons. The ratio of 10Be/7Be is used to estimate effects of air mass transport on production signal. The results show ratios between 1 and 3, much higher than the theoretically predicted value (0.6) in the atmosphere, which suggests contribution from 7Be-depleted (old) air masses. The relationship between monthly 7Be atmospheric activity and Total Fractional Cloud Cover (TFCC), collected from satellite imagery, over Sweden for the years (1991-2000) indicates a negative seasonal correlation. This observation can be related to depletion of aerosol from the atmosphere due to trapping in clouds.

No description available.