Diatom response to mid-Holocene climate change in Lago di Massaciuccoli (Tuscany,Italy)

A sedimentary sequence from the Mediterranean coastal basin of Lago di Massaciuccoli (Tuscany, Italy) was analyzed for diatoms, covering two periods over the past ca. 7,000 years. The site was selected because it is situated in a sensitive position at the limit between Mediterranean and Central European climates and biomes. Our focus is on the impact of accelerated human activity during the recent past (water uptake in the catchment, sand extraction, wastewater discharge) and on a phase of evident change between 6,600 and 5,400 cal. BP. The diatom record suggests fresh-water conditions and rather high lake levels until ca. 6,000 years ago. The subsequent shift towards brackish conditions peaked at around 5,500 cal. BP. We relate this shift to a pervasive change towards a drier climate that has been observed elsewhere in the Mediterranean and Northern African regions, and stands in contrast to the shift towards a cooler and more humid climate in the nearby Alps (200–350 km distant) and in central Europe. Pollen and charcoal records from a previous study on the same sedimentary sequence were used to gain additional insights about the causes of the changes in the diatom assemblages and apply numerical methods to search for common trends and correlations.     

Inorganic nitrogen control in wastewater treatment ponds from a fish farm (Orbetello, Italy): denitrification versus Ulva uptake

The aim of this study was to quantify the N removal efficiency of an Ulva-based phytotreatment system receiving wastewaters from a land-based fish farm (Orbetello, Italy), to identify the main biogeochemical pathways involved and to provide basic guidelines for treatment implementation and management. Fluxes of O2 and nutrients in bare and in Ulva colonised sediments were assessed by light/dark core incubations; denitrification by the isotope pairing technique and Ulva growth by in situ incubation of macroalgal disks in cages. O2 and nutrient budgets were estimated as sum of individual processes and further verified by 24-h investigations of overall inlet and outlet loads. Ulva uptake (up to 7.8 mmol Nm(-2) h(-1)) represented a net sink for water column and regenerated NH4+ whilst N removal via denitrification (10-170 micromol Nm(-2) h(-1)) accounted for a small percentage of inorganic nitrogen load (<5%). Laboratory experiments demonstrated a high potential for denitrification (over 800 microM Nm(-2) h(-1)) indicating that N loss could be enhanced. The control of Ulva standing stocks by optimised harvesting of surplus biomass may represent an effective strategy to maximise DIN removal and could result in the assimilation of approximately 50% of produced inorganic nitrogen.     

Effusive Activity at Mount Etna Volcano (Italy) During the 20th Century: A Contribution to Volcanic Hazard Assessment

Mount Etna is an open conduit volcano, characterised by persistent activity, consisting of degassing and explosive phenomena at summit craters, frequent flank eruptions, and more rarely, eccentric eruptions. All eruption typologies can give rise to lava flows, which represent the greatest hazard by the volcano to the inhabited areas. Historical documents and scientific papers related to the 20th century effusive activity have been examined in detail, and volcanological parameters have been compiled in a database. The cumulative curve of emitted lava volume highlights the presence of two main eruptive periods: (a) the 1900–1971 interval, characterised by a moderate slope of the curve, amounting to 436 × 10⁶ m³ of lava with average effusion rate of 0.2 m³/s and (b) the 1971–1999 period, in which a significant increase in eruption frequency is associated with a large issued lava volume (767 × 10⁶ m³) and a higher effusion rate (0.8 m³/s). The collected data have been plotted to highlight different eruptive behaviour as a function of eruptive periods and summit vs. flank eruptions. The latter have been further subdivided into two categories: eruptions characterised by high effusion rates and short duration, and eruptions dominated by low effusion rate, long duration and larger volume of erupted lava. Circular zones around the summit area have been drawn for summit eruptions based on the maximum lava flow length; flank eruptions have been considered by taking into account the eruptive fracture elevation and combining them with lava flow lengths of 4 and 6 km. This work highlights that the greatest lava flow hazard at Etna is on the south and east sectors of the volcano. This should be properly considered in future land-use planning by local authorities.     

Noble gas study of a philippinite with an unusually large bubble

Abstract— A philippinite with a large bubble (volume ?5 cm³) was crushed in a specifically constructed device under vacuum. The total pressure, the major gas components, and the concentration and the isotopic composition of noble gases in the trapped gas were measured. The total gas pressure was found to be low, ～10^?4 atm. Compared to terrestrial atmosphere, the abundances of He and Ne are considerably more enriched than the concentrations of the heavy noble gases. Unusually high ²⁰Ne/²²Ne and ²¹Ne/²²Ne ratios were measured in the bubble gas. These ratios are higher than values expected for any steady state process and are interpreted to reflect very fast nonsteady state diffusion in the early stages of tektite formation.     

New chronological and geochemical constraints on the genesis and geological evolution of Ponza and Palmarola Volcanic Islands (Tyrrhenian Sea, Italy)

A new geochronological and geochemical study of the volcanic rocks of the Ponza and Palmarola Islands, Pontine Archipelago, has been carried out. This archipelago is located along the boundary between the Italian continental shelf and the opening Tyrrhenian basin. It is a key area to study volcanism related to the opening of the Tyrrhenian Sea. Ponza is the oldest felsic magmatic manifestation in the central Tyrrhenian area. Previous studies suggested that Ponza volcanic activity began before 5 Ma. Twenty-five new K–Ar ages constrain the volcanic activity (rhyolitic hyaloclastites and dykes) to the last 4.2 Ma, with two episodes of quiescence between 3.7 and 3.2 Ma and between 2.9 and 1.0 Ma. A new volcanic episode dated at 3.2–2.9 Ma has been identified on the central and southern Ponza, with emplacement of pyroclastic units. At 1.0 Ma, a trachytic episode ended the volcanic activity. The near island of Palmarola exhibits rhyolitic hyaloclastites and domes dated between 1.6 and 1.5 Ma, indicating that the island was entirely built during the Early Pleistocene in a short span of time of ca. 120 ka. Although only 6–8 km apart, the two islands display significantly different geochemical signatures. Ponza rhyolites show major and trace element compositions representative of orogenic magmas of subduction/collision zones: high-K calc-alkaline and metaluminous rhyolites (Agpaitic Index [AI] and Alumina Saturation Index [ASI] <1), high LILE/HFSE (Th/Ta=16–21) and LREE/HFSE ratios (La/Nb>3), and Nb–Ta negative anomalies. In Palmarola, the orogenic character is also present, but much less marked than in Ponza: rhyolites have a peralkaline character (AI>1), lower LILE/HFSE (Th/Ta=11–15), low LREE/HFSE ratios (La/Nb=1–2) close to those of anorogenic lavas, and the Nb–Ta negative anomalies are almost absent. Y/Nb ratios indicate different magmatic sources, one similar to island-arc or active continental margin basalts for Ponza rhyolites, and the others probably involving an OIB type component for Palmarola rhyolites and Ponza trachytes. Palmarola volcanics represent a transitional magmatism: although a preserved collisional geochemical imprint, they show geochemical features approaching those of anorogenic lavas erupted in a within-plate context. The change of magmatism evidenced in this study can be related to the tectonic evolution of the area. Indeed, Hf, Ta and Rb contents suggest that the oldest Pliocene rhyolites of Ponza would emplace in a syn- to late-collisional setting, while the younger Pleistocene rhyolites of Palmarola would be emplaced in a post-collisional setting in which the orogenic character (Th/Ta) decreases and mantle influence (Nb/Ta) increases. Geochemical modeling strongly suggests that the Palmarola rhyolites represent the waning stages of a subduction-related magmatism. The K–Ar datings allow us to estimate precisely the transition of magmatism to last less than 1.3 Ma. The transitional magmas may be the result of the upwelling of asthenospheric mantle inducing melting of a metasomatized lithospheric mantle and the mixing between these two sources. This upwelling could occur during the extension of the Tyrrhenian basin, caused by the slab retreat and steepening, or during a process of slab break-off starting in the Pliocene.     

Historical geospatial database for landslide analysis: the Catalogue of Landslide OCcurrences in the Emilia-Romagna Region (CLOCkER)

A review of the content, structure, accuracy, and completeness of the Catalogue of Landslide OCcurrences in the Emilia-Romagna Region (CLOCkER) is presented. CLOCkER is a historical database, designed and developed for all types of landslides in the hilly-mountain area of the Emilia-Romagna section of the Northern Italian Apennines. Historical data have been gathered through a collection of numerous sources, including technical reports, historical archives, scientific literature, and newspapers. The information obtained, which has been evaluated to assess its temporal precision and spatial accuracy, has been recorded in a catalogue consisting of a Database Management System (DBMS) linked to a geographical information system (GIS) interface. The catalogue presently includes 14,416 records of documented landslide occurrences, dating from Middle Ages up to the present. The catalogue is associated with a landslide inventory, continuously updated by the Geological Survey of the Emilia-Romagna Region, where information on the shape, typology, and state of activity of more than 80,000 landslides is included. Our assessment of catalogue quality reveals a satisfactory spatial accuracy and a level of completeness comparable with the theoretical target proposed in the literature for complete inventories. Outputs indicate that CLOCkER can be a reference example useful for other regional historical landslide catalogues. Such reference datasets are useful for a wide range of landslide assessment purposes and can provide practical assistance for stakeholders involved in both scientific and technical fields, forming the basis for landslide temporal trend reconstruction that is essential for landslide hazard evaluation at different spatial-temporal scales. CLOCkER is open access, freely available online.