Description: The aim of the present work was to unravel which environmental drivers govern the dynamics of toxic dinoflagellate abundance as well as their associated paralytic shellfish toxins (PSTs), diarrhetic shellfish toxins (DSTs) and pectenotoxin-2 (PTX2) in Ambon Bay, Eastern Indonesia. Weather, biological and physicochemical parameters were investigated weekly over a 7-month period. Both PSTs and PTX2 were detected at low levels, yet they persisted throughout the research. Meanwhile, DSTs were absent. A strong correlation was found between total particulate PST and Gymnodinium catenatum cell abundance, implying that this species was the main producer of this toxin. PTX2 was positively correlated with Dinophysis miles cell abundance. Vertical mixing, tidal elevation and irradiance attenuation were the main environmental factors that regulated both toxins and cell abundances, while nutrients showed only weak correlations. The present study indicates that dinoflagellate toxins form a potential environmental, economic and health risk in this Eastern Indonesian bay.

Description: Against the background of a drastically increased demand of marine proteins, off-bottom, bivalve aquaculture, provides significant potential for production growth when moved into more energetic marine waters. Hence, research, industry and politics are currently proposing the development of new offshore sites. The highly energetic conditions at these sites present a challenging environment for bivalve aquaculture. In this work, physical experiments of suspended bivalves provide new knowledge on the commonly used design parameters: the drag and inertia coefficients. Live bivalves and manufactured surrogate models at a 1:1 scale were tested in a towing tank as well as under waves. The drag coefficient of live blue mussels was determined to be Cd = 1.6 for Reynolds numbers between 2.3 × 104 and 1.4 × 105. The inertia coefficient obtained from the wave tests was Cm = 2.1 for Keulegan Carpenter numbers KC 〈 10. In a pursuit to better understand the differences between live mussels and surrogates in laboratory conditions, the analysis revealed that appropriate surrogates can be identified. A method to determine the characteristic diameter of mussel dropper lines is suggested. The results facilitate the future design of aquaculture systems in high-energy environments and allow for an integration into numerical models.

Description: Lake eutrophication is a pervasive problem globally, particularly serious in agricultural and densely pop- ulated areas. Whenever nutrients nitrogen and phosphorus do not limit phytoplankton growth directly, high growth rates will rapidly lead to biomass increases causing self-shading and light-limitation, and eventually CO2 depletion. The paradigm of phytoplankton limitation by nutrients and light is so perva- sively established, that the lack of nutrient limitation is ordinarily interpreted as sufficient evidence for the condition of light limitation, without considering the possibility of limitation by inorganic carbon. Here, we firstly evaluated how frequently CO2 undersaturation occurs in a set of eutrophic lakes in the Pampa plains. Our results confirm that conditions of CO2 undersaturation develop much more frequently (yearly 34%, summer 44%) in these agriculturally impacted lakes than in deep, temperate lakes in forested watersheds. Secondly, we used Generalized Additive Models to fit trends in CO2 concentration considering three drivers: total incident irradiance, chlorophyll a concentration, and lake depth; in eight multi-year datasets from eutrophic lakes from Europe, North and South America, Asia and New Zealand. CO2 deple- tion was more often observed at high irradiance levels, and shallow water. CO2 depletion also occurred at high chlorophyll concentration. Finally, we identified occurrences of light- and carbon-limitation at the whole-lake scale. The different responses of chlorophyll a and CO2 allowed us to develop criteria for detecting conditions of CO2 limitation. For the first time, we pro- vided whole-lake evidence of carbon limitation of phytoplankton biomass. CO2 increases and eutrophi- cation represent two major and converging environmental problems that have additive and contrasting effects, promoting phytoplankton, and also leading to carbon depletion. Their interactions deserve further exploration and imaginative approaches to deal with their effects.

Description: In the field of risk evaluation and seismic hazard assessment, it is necessary to codify a great quantity of aspects of the so called knowledge and to supply an intelligent support for the not-well-defined problems (data uncertainty, lack of rigorous solution algorithms). The main feature of an expert system is to emulate effectively the behaviour of a human expert in a particular and defined field, enabling the final user to improve its decisional process and giving access to him to a knowledge base otherwise not clearly codified. From these general considerations the intention came to develop the prototype CZAR (Classificatore Zone A Rischio) that is an expert system reproducing the Italian seismic classification based on the definition of Seismic Hazard given by Progetto Finalizzato Geodinamica (PFG) of the Consiglio Nazionale delle Ricerche (CNR). The expert system built up on the commercial shell Nexpert Object is working on a personal computer through a graphic interface developed with the Graphical User Interface (GUI) of Window 3.0. This user friendly interface makes possible the choice of different procedures to estimate the hazard parameters and also allows the activation of the classification inferential process. The influence of different assumptions and strategies has been evaluated by a mathematical algorithm suggested by the general structure of the Bayes’ theorem. In this paper the prototype of the expert system has been applied to the data relating to Toscana region (central Italy) and the interactive evaluation of the maps furnishes a relative measure for discrepancies on seismic classification in the 2nd seismic category.

Description: Published

Description: 153-173

Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica

Description: The Southern Ocean near the Western Antarctic Peninsula (WAP) is strongly affected by climate change resulting in warmer air temperature, accompanied with reduced sea ice coverage, increased sea water temperature and potential changes in the abundances of two key grazer species Salpa thompsoni (salp) and Euphausia superba (Antarctic krill). While salp abundance is hypothesized to increase, krill abundance is hypothesized to decline with dramatic consequences for the entire food web of the Southern Ocean. A better understanding of the biotic interaction between krill and salps and their population dynamics is thus crucial. However, the life cycle of salps is complicated and barely understood. Therefore, we have developed an individual-based model describing the whole life cycle to better understand the population dynamics of salps and the conditions for blooms. The model has been used to explore if and under what conditions the empirical pattern of large variability in observed salp abundances at the WAP, generated by the long-term data of the US Antarctic Marine Living Resources Program (AMLR) can emerge from a small seeding population. The model reproduced this empirical pattern if daily growth rates of oozoids were higher than previously reported for the WAP (mean growth rate for oozoids ~ 1 mm d−1) and if growth rates of blastozooids were lower (mean growth rate ~ 0.2 mm d−1). The model suggests that a prerequisite for local salp blooms requires a small founding population in early spring. With climate change it has been suggested that more frequent and earlier transport of salps into the WAP or winter survival will occur. Hence, the risk of salp blooms in the WAP is likely to substantially increase. These findings highlight the importance for an improved quantitative understanding of how primary production and the southward advection of salps will be impacted by climate change.

Description: The analysis of damage on buildings affected by an earthquake allow to trace back to the defects of the structural system and the imperfections of the constructive elements with reference to the best or worst behaviour in case of seismic action. As a matter of fact the tendency of buildings to be damaged, also defined as seismic vulnerability, is strictly connected with their geometric-constructive characteristics. The damage appears as "effect" of the phenomenon that has its "cause" in the seismic action. Once the characteristics of the system are defined, it is possible to reconstruct the 'cause-effect' relation between seismic action and damage. These relations can be obtained through survey of damage caused by recent earthquake. However this methodology reveals a series of problems. The various quantities applied must be expressed with indices that allow to synthesize complex and articulated scenarios exhaustively; although the damage is a quantity that can be directly assessed by description, it is difficult to measure, as its quantification should be representative for all aspects connected with it (physical, economic, functional, social, etc.). The level of the seismic action must be expressed by a parameter that is an index of the event's destructive capacity and in direct correlation with mechanical quantities (acceleration, velocity, energy, etc.). The vulnerability is an entity able to characterize the more or less accentuated predisposition of the structures to suffer damages independently from the intensity and direction of the seismic action. In this work, subjects concerning seismic action and vulnerability shall not be dealt with, as they have already been investigated in previous works [see Grimaz S., 1992 - Cella F. 1994 and 1995]; in the following the problem of damage quantification shall therefore be explored.

Description: Published

Description: 83-103

Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica

Description: The studies urban areas directed at the definition of seismic risk, raise the problem of the seismic vulnerability assessment of construction properties that require the estimation of the tendency to damage of a plurality of buildings. Very often one comes upon buildings that have been constructed in former epochs without the use of seismic codes and generally built in masonry. The leads to the search for procedures for vulnerability assessment, based on the rapid acquisition of information on existing buildings, which must furnish a sufficiently reliable assessment of the seismic damageability, generally without the possibility to refer to very sophisticated models. In previous works, assessments of seismic vulnerability have been effected using surveys transferred on National Project for Seismic Prevention (GNDT) sheets (Zonno and Ducarme, eds, 1992). These works have been realized using capes systems in order to treat with the uncertainty of the data. However, the analyses that only refer to GNDT sheets, are limited to single buildings, ideationally understood as isolated. An alternative and maybe complementary attempt is to assess the vulnerability of buildings in a global structural context using Geographic Information Systems to mapping the urban system, integrated with the surveys transferred on COOT sheets. The main characteristics of the building and the structural context, indices of a major or minor damageability, have been individuated, but it is difficult to define a rapid procedure for the assessment of seismic vulnerability. The idea was to use an expert system to codify a basis of the presently acquired knowledge and to apply it automatically on the basis of the results obtained by processes of space analyses calculated by GIS. On the basis of the data obtained with GNDT sheets, the vulnerability of the building can be assessed independently from the structural context (intrinsic vulnerability). The availability of data on the space distribution of the adjoining buildings permits an assessment on the effective vulnerability that takes into account the influence of the structural context. With relation to other works effected on the argument, the proposed system automatically assesses a large quantity of geocoded data either in geometry and in the structure of the components. In particular, in this work the seismic vulnerability assessment of the buildings is effected through the Geographic Information Systems PC Arc-Info connected with the Expert System Shell Nexpert Object, starting from the methods used by the GNDT of the National Council for Research (CNR) (Benedetti and Petrini, 1984; Baldi and Corsanego, 1987) and integrating the effects of anisotropics of the structural behaviour and context (Grimaz, 1992-93).

Description: Published

Description: 105-128

Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica

Description: During the 1-year MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition, the German icebreaker Polarstern drifted through Arctic Ocean ice from October 2019 to May 2020, mainly at latitudes between 85 and 88.5∘ N. A multiwavelength polarization Raman lidar was operated on board the research vessel and continuously monitored aerosol and cloud layers up to a height of 30 km. During our mission, we expected to observe a thin residual volcanic aerosol layer in the stratosphere, originating from the Raikoke volcanic eruption in June 2019, with an aerosol optical thickness (AOT) of 0.005–0.01 at 500 nm over the North Pole area during the winter season. However, the highlight of our measurements was the detection of a persistent, 10 km deep aerosol layer in the upper troposphere and lower stratosphere (UTLS), from about 7–8 to 17–18 km height, with clear and unambiguous wildfire smoke signatures up to 12 km and an order of magnitude higher AOT of around 0.1 in the autumn of 2019. Case studies are presented to explain the specific optical fingerprints of aged wildfire smoke in detail. The pronounced aerosol layer was present throughout the winter half-year until the strong polar vortex began to collapse in late April 2020. We hypothesize that the detected smoke originated from extraordinarily intense and long-lasting wildfires in central and eastern Siberia in July and August 2019 and may have reached the tropopause layer by the self-lifting process. In this article, we summarize the main findings of our 7-month smoke observations and characterize the aerosol in terms of geometrical, optical, and microphysical properties. The UTLS AOT at 532 nm ranged from 0.05–0.12 in October–November 2019 and 0.03–0.06 during the main winter season. The Raikoke aerosol fraction was estimated to always be lower than 15 %. We assume that the volcanic aerosol was above the smoke layer (above 13 km height). As an unambiguous sign of the dominance of smoke in the main aerosol layer from 7–13 km height, the particle extinction-to-backscatter ratio (lidar ratio) at 355 nm was found to be much lower than at 532 nm, with mean values of 55 and 85 sr, respectively. The 355–532 nm Ångström exponent of around 0.65 also clearly indicated the presence of smoke aerosol. For the first time, we show a distinct view of the aerosol layering features in the High Arctic from the surface up to 30 km height during the winter half-year. Finally, we provide a vertically resolved view on the late winter and early spring conditions regarding ozone depletion, smoke occurrence, and polar stratospheric cloud formation. The latter will largely stimulate research on a potential impact of the unexpected stratospheric aerosol perturbation on the record-breaking ozone depletion in the Arctic in spring 2020.

Description: Low-level mixed-phase clouds (MPCs) are common in the Arctic. Both local and large-scale phenomena influence the properties and lifetime of MPCs. Arctic fjords are characterized by complex terrain and large variations in surface properties. Yet, not many studies have investigated the impact of local boundary layer dynamics and their relative importance on MPCs in the fjord environment. In this work, we used a combination of ground-based remote sensing instruments, surface meteorological observations, radiosoundings, and reanalysis data to study persistent low-level MPCs at Ny-Ålesund, Svalbard, for a 2.5-year period. Methods to identify the cloud regime, surface coupling, and regional and local wind patterns were developed. We found that persistent low-level MPCs were most common with westerly winds, and the westerly clouds had a higher mean liquid (42 g m−2) and ice water path (16 g m−2) compared to those with easterly winds. The increased height and rarity of persistent MPCs with easterly free-tropospheric winds suggest the island and its orography have an influence on the studied clouds. Seasonal variation in the liquid water path was found to be minimal, although the occurrence of persistent MPCs, their height, and their ice water path all showed notable seasonal dependency. Most of the studied MPCs were decoupled from the surface (63 %–82 % of the time). The coupled clouds had 41 % higher liquid water path than the fully decoupled ones. Local winds in the fjord were related to the frequency of surface coupling, and we propose that katabatic winds from the glaciers in the vicinity of the station may cause clouds to decouple. We concluded that while the regional to large-scale wind direction was important for the persistent MPC occurrence and properties, the local-scale phenomena (local wind patterns in the fjord and surface coupling) also had an influence. Moreover, this suggests that local boundary layer processes should be described in models in order to present low-level MPC properties accurately.