ENEA Saluggia Research Centre

The study on the migrations of the confluence between the rivers Po and Dora Baltea was based on a detailed observation of aerial photographs, field surveys and sediment stratigraphy. The age of the sediments and morphological features was based on radiocarbon datings, on the presence of archaeological settlements and ancient artefacts and on historical data. The aerial photographs of the GAI 1954 flight of the Italian Air Force were used because in the year 1954, some low terraces were still clearly visible, while today are almost completely obliterated because of the works for the improvement of the rice fields. A succession of nine fluvioglacial and fluvial terraces and many abandoned riverbeds have been identified: the interpretation of the morphological features made it possible to identify the Po and Dora Baltea evolution during the late Holocene. The study established that during the last 3000 years, the confluence of the Dora Baltea into the Po has constantly migrated to the west and that this migration occurred during alluvial phases dating back to the Iron Age, 2nd century BC–1st century AD, 5th century AD, 6th–8th century AD and 15th–19th century AD. The alluvial phases occurred during periods of increased floods in northern Italy and advances of the Alpine glaciers in northwestern Italy and Switzerland. Neither tectonic deformations nor anthropic actions seem to have influenced fluvial evolution in the last 3000 years. The westward migration of the confluence between the rivers was therefore triggered by climatic changes, but caused by the different responses of the catchments of the Dora Baltea and the Po rivers to climatic changes, and by the greater slope of the Dora Baltea flood plain.

The assessment of compositional differences between bryophyte communities from different fluvial regions should ideally be achieved using biologic and environmental field data from standardized pan-European surveys. Since aquatic bryophyte communities result from interactive effects of local environmental filters, larger climatic filters and anthropogenic stressors, we aimed to explore the compositional segregation of bryophyte communities across three Mediterranean regions (Environmental Stratification of Europe; Metzger et al. GEB 14: 549-563). We used floristic data collected for intercalibration purposes under the EU Water Framework Directive and data from River Habitat Survey of 474 Mediterranean sites (99 South, 246 North; 129 Mountains). Applying TWINSPAN, SIMPER and ANOSIM analysis, we compared assemblages between Mediterranean climatic regions and identifyed indicator taxa. TWINSPAN revealed four distinct groups after two divisions which do not strictly separate sites according to climatic regions, indicating other underlying ecological compostional determinants. Bryophytic composition reveals that sites of different climatic zones share hydrologic and geomorphologic features, creating niche for shared core taxa and other region-specific taxa responsible for each region singularity. This results reinforce the importance of fluvial landscape heterogeneity conservation for the sustainability of European aquatic bryophyte richness and diversity.

ABSTRACT A preliminary evaluation of gaseous radiocarbon ( 14 C) behavior under geological repository conditions for Italian radioactive high level waste-long-lived and intermediate level waste disposal has been performed. Although in Italy there is still no defined project for a geological disposal facility, current work may support future safety assessment studies for a hypothetical future repository in deep salt rock. In the Italian context of radioactive waste, the percentage of 14 C bearing waste to be disposed in a possible geological repository is low; irradiated graphite is the most important radiological source. Data about the radiological inventory has been collected to simulate production and migration of gaseous 14 C in a hypothetical geological repository. Three different conceptual models have been developed and simulated. The first model has considered a preliminary evaluation of the radiological impact referred to the whole inventory; the second and third model have evaluated the impact only due to the irradiated graphite. A preliminary sensitivity analysis has been carried out, highlighting the importance of geometry and of distribution coefficients (K d ) in materials used to seal the disposal underground facility. Results show the possibility to correlate the K d values, the volume and the location of the sealing materials to the amount of 14 C migrating toward the surface.