Choosing a rockfall barrier with the Precautionary Principle: a quantitative approach

The paper illustrates an approach for implementing the Precautionary Principle in risk management, exemplified by a procedure aimed at choosing the height of a rockfall barrier protecting a railway stretch. Risk is expressed by the frequency f of blocks hitting the railway—i.e. by the ratio between the number of blocks reaching the railway and the number of blocks falling from the slope—assessed through software simulation of the falling of the blocks. The height from which a block may fall is considered to be the main uncertainty factor in risk estimation, which translates into uncertainty as to the level of risk, as every simulation shows that more than one impact frequency is possible. Such uncertainty justifies the precautionary approach to the design of the barrier, and is represented mathematically by means of possibility and probability distribution functions. The distributions make it possible to express the degree of precaution related to a barrier as the level of confidence, in terms of necessity or probability measures—that can be placed on the fact that, because of the barrier, the impact frequency, although uncertain, will not exceed what is acceptable. It will be shown that the degree of precaution takes quite different values if possibility theory is used instead of probability theory. Finally some simple cost/benefit analyses, that explicitly and quantitatively consider the degree of precaution, are exemplified.     

Chemical composition of wet and dry atmospheric depositions in an urban environment: local,regional and long-range influences

The results of a 8 year survey of wet and dry depositions collected in Bologna (Northern Italy) are presented and discussed: monthly fluxes of the main ions (hydrogen, sodium, potassium, calcium, magnesium, ammoniacal and nitrate nitrogen, sulphate and chloride) have been registered and statistically discussed. The trend of hydrogen ion, whose largest correlation in the global deposition was found with sulphate, is clearly downwards, with peaks mainly in winter months. By means of a data factor analysis, three main sources to explain the variability of the deposition chemistry were recognized: an anthropogenic contribution (particularly represented by NO₃ ⁻, SO₄ ²⁻, H⁺), the sea spray (Na⁺, Cl⁻ and, to a lesser extent, K⁺ and Mg²⁺) and a terrigenous fraction, particularly characterized by higher Ca²⁺ concentration; however, some concentration peaks of this ion have been found in association with some episodes of Saharan dust transportation.     

Trace elements and ions in Italian bottled mineral waters: Identification of anomalous values and human health related effects

Microbiological studies have always had an important role in the evaluation of drinking water quality. However, since geological processes are the most important factors controlling the source and distribution of chemical elements in natural waters, the importance of geochemical data must not be underestimated. This study presents data on pH, conductivity and concentrations of 69 elements and ions (Ag, Al, As, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, K, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Se, Sm, Sn, Sr, Ta, Tb, Te, Th, Ti, Tl, Tm, U, V, W, Y, Yb, Zn, Zr, Br⁻, HCO₃⁻, Cl⁻, F⁻, NH₄⁺, NO₂⁻, NO₃⁻, PO₄³⁻, SO₄²⁻, SiO₂) from 186 bottled mineral waters of 158 different Italian name brands. Analyses show a large range in concentrations for most of these elements, with variations up to four orders of magnitude. Our data demonstrate that some elements (such as Be), generally considered unlikely to occur, can instead reach surprisingly high levels in drinking water, and also how packaging can release some trace elements to the bottled water. Data analysis shows that the implementation of an international database of bottled water geochemistry and of potential toxicological effects is of paramount importance to provide a robust data set which would be useful to set international action levels and guidelines to secure bottled water quality, whose consumption has steadily increased in the recent years. A new formula to calculate nitrate and nitrite tolerable concentration levels in waters intended for human consumption is proposed, to take into account that about 5% of dietary nitrate in humans is converted to nitrite.     

Chandra unveils a binary active galactic nucleus in Mrk 463

We analyse Chandra , XMM–Newton and Hubble Space Telescope ( HST ) data of the double-nucleus Ultraluminous Infrared Galaxy (ULIRG), Mrk 463. The Chandra detection of two luminous  ( L _2–10 keV= 1.5 × 10⁴³  and  3.8 × 10⁴² erg cm⁻² s⁻¹)  , unresolved nuclei in Mrk 463 indicates that this galaxy hosts a binary active galactic nucleus (AGN), with a projected separation of ≃3.8 kpc (  3.83 ± 0.01  arcsec). While the East nucleus was already known to be a type 2 Seyfert (and this is further confirmed by our Chandra detection of a neutral iron line), this is the first unambiguous evidence in favour of the AGN nature of the West nucleus. Mrk 463 is therefore the clearest case so far for a binary AGN, after NGC 6240.     

Interplay between stress permutations and overpressure to cause strike‐slip faulting during tectonic inversion

Field data from an orogenic foreland and an orogenic belt (the Mesozoic rocks of southern England and the Umbria‐Marche Apennines of Italy respectively) indicate the following. Firstly, stress evolution during the tectonic cycle, between maximum compressive stress (σ₁) being vertical during extension and least compressive stress (σ₃) being vertical during contraction, can involve phases when the intermediate compressive stress (σ₂) is vertical, promoting strike‐slip deformation. Secondly, variations in the relative magnitudes of the stress axes are caused by variations in overburden and tectonic forces. Thirdly, overpressure can develop because of compaction during burial, and, as overburden is reduced during uplift and erosion, the vertical stress (σ_V) reduces but fluid pressure (P_f) remains approximately constant. Brittle deformation, including transient strike‐slip faults, reverse‐reactivated normal faults and normal‐reactivated thrusts, is preferentially developed in overpressured areas because high P_f promotes faulting.     

Intrinsic vulnerability assessment of Saturnia thermal aquifer by means of three parametric methods: SINTACS,GODS and COP

Three different parametric methods for the evaluation of intrinsic vulnerability to pollution have been applied in a hydrothermal carbonate aquifer located in central-northern Italy and the results obtained were compared with each other. The study area, large, approximately 152 km², lies in an area of the northern Apennines. The investigated aquifer feeds the hot thermal springs of Saturnia. The vulnerability assessment methods used are: SINTACS, GODS and COP. The vulnerability maps obtained were first individually examined, and then they were compared with each other by means of spatial analysis. These maps show similar results for the estimation of the vulnerability just in some areas. SINTACS yields areas potentially vulnerable to pollution along the Albegna River and its major tributaries in the northern part of the study area. The GODS index map reflects the great importance that this method gives to the lithological characteristics of the unsaturated zone in the subdivision of areas with different vulnerability. GODS and COP methods agree in classifying low vulnerability in the most part of central-southern study area, where the aquifer is confined by the Pliocene clay deposits. Based on the conceptual model of groundwater flow developed for the aquifer under investigation, COP seems the most appropriate method among those applied in this work, in particular with regard to the assessment of the vulnerability of the recharge area of thermal groundwater. Located in the northern part of the study area, where karst carbonate formations of the Tuscan Nappe outcrop, this recharge area is classified by the COP method as highly vulnerable to pollution.     

On the reliability of the equivalent frame models: the case study of the permanently monitored Pizzoli’s town hall

Bulletin of Earthquake Engineering - This paper presents the comparison of the results of modal and nonlinear analyses carried out on a 2-story masonry building with rigid diaphragms, inspired by...     

Time-dependent reliability analysis of unsaturated slopes under rapid drawdown with intelligent surrogate models

Acta Geotechnica - Slope stability in reservoirs depends on time-dependent triggering factors such as fluctuations of the groundwater level and precipitation. This paper assesses the stability of...     

An Advanced Systematic Literature Review on Spatiotemporal Analyses of Twitter Data

The objective of this article is to conduct a systematic literature review that provides an overview of the current state of research concerning methods and application for spatiotemporal analyses of the social network Twitter. Reviewed papers and their application domains have shown that the study of geographical processes by using spatiotemporal information from location‐based social networks represent a promising and still underexplored field for GIScience researchers.