Some limitations in using <Superscript>222</Superscript>Rn to assess river–groundwater interactions: the case of Castel di Sangro alluvial plain (central Italy)

²²²Rn was used to assess river–groundwater interactions within Castel di Sangro alluvial aquifer (Italy). The effectiveness of results obtained through this indicator was verified by also analyzing δ¹⁸O, major ions and temperature in both surface and groundwater, and carrying out piezometric head monitoring and discharge measurements. Hydrogeological investigations suggested that the river infiltrates into the aquifer in the south-eastern aquifer portion, while groundwater discharges into the river in the north-eastern portion. The latter phenomenon is supported by ²²²Rn data. Nevertheless, flow-through conditions cause the modelled discharge along this river reach, estimated by ²²²Rn data in a degassing-corrected two-component mixing model, to be greater than the measured discharge. Concerning river infiltration into the aquifer, δ¹⁸O, major ions and temperature data show that the river contribution is negligible in terms of aquifer recharge. Thus, the observed increase in ²²²Rn concentration in that portion of the aquifer is due to the enrichment process caused by infiltration of rainwater (²²²Rn free) which flows from the local divide area. Hence, in the study site, the use of only ²²²Rn to predict river–groundwater interactions causes some estimation inaccuracies and it must be coupled with other hydrochemical and hydrogeological parameters to gain a thorough understanding of such interactions.     

Towards incorporating a turbulent magnetic field in an accreting black hole model

A model proposed by Melia & Ruffert to evaluate the spectrum and radiation flux for accretion on to a black hole makes use of the 'equipartition assumption' in which the magnetic, turbulent and gravitational energy densities are assumed to be in approximate equilibrium for distances below the accretion radius, where Bondi–Hoyle infall begins. As a consequence, the mechanism for the dissipation of the magnetic field and the resulting effect on the flow of the accreting gas have not been treated quantitatively. Here we examine alternative approaches for modelling the dissipation of magnetic fields and turbulent flow to see how these may be incorporated into the model. The results of our study should be immediately applicable to the ever-improving measurements of the spectrum and size of the massive black hole at our Galactic Centre, in particular producing a more accurate estimate of its mass. Combined with greatly refined kinematic studies of this region, our work may constrain the dark matter concentration in the nucleus of our Galaxy.     

Heuristic considerations pertaining to hailstone size distributions in the plain of Friuli-Venezia Giulia

In this work, the hailstone size distributions at the ground in the plain of Friuli-Venezia Giulia are presented, as revealed through a network of polystyrene pads (hailpads), managed by volunteers, which has been active since 1988. The aim of this work is to highlight possible differences in the diurnal and seasonal behavior of hail at the ground, both from Friuli-Venezia Giulia and other countries, in order to improve the knowledge of this meteorological phenomenon.In the comparison between different countries, differences are found between the yearly size distributions of Friuli-Venezia Giulia and those of North-East Colorado, measured during the National Hail Research Experiment (NHRE). The size distributions obtained in South West France and in Friuli-Venezia Giulia are quite similar and they are slightly different from those of the Grossversuch experiment.In the comparison between different periods of the year, relevant differences are found between April and May and the other months. In particular, thunderstorms are less efficient in producing big hailstones during the former months. The most prolific month in producing hailstones is June, followed by September. This feature is interpreted as due to a form of synergy between the frequency of the synoptic forcing of storms and the amount of available energy at the ground.Analyzing the size distributions at different times of the day, the greatest differences are found in the intervals [00–06] and [06–12] in local time (respectively, [22–04] and [04–10] in UTC). These differences cannot be ascribed to the melting of the hailstones during their fall.     

Pretunnel technology: applications and design methods

The Pretunnel technology allows the final or preliminary lining to be built ahead of a tunnel face. The paper shows how this technology has been used for mechanizing the full-face excavation of large tunnels in difficult ground conditions with minimum settlements. Analytical methods are presented for the analysis of the lining both in deep and shallow applications. Fields of applicability are established using results of parametric studies based on the methods proposed.     

Coupling of BEM with a large displacement and rotation algorithm

In stability analysis of rock blocks, the deformability of the blocks can conveniently be simulated using the boundary element method (BEM). However, all boundary conditions are given as stresses. Thus, the displacement solution is not unique. In this paper, an algorithm is proposed to remove rigid body motions in the solution of the boundary form of Somigliana identity discretized by the direct BEM formulation. The algorithm is applied to the calculation of the normal stiffness of rock blocks and coupled with BS3D, large displacement and rotation algorithm for the general stability of rock blocks. Copyright © 2010 John Wiley & Sons, Ltd.     

Groundwater-surface water interactions: New methods and models to improve understanding of processes and dynamics

Interest in groundwater (GW)-surface water (SW) interactions has grown steadily over the last two decades. New regulations such as the EU Water Framework Directive (WFD) now call for a sustainable management of coupled ground- and surface water resources and linked ecosystems. Embracing this mandate requires new interdisciplinary research on GW-SW systems that addresses the linkages between hydrology, biogeochemistry and ecology at nested scales and specifically accounts for small-scale spatial and temporal patterns of GW-SW exchange. Methods to assess these patterns such as the use of natural tracers (e.g. heat) and integrated surface-subsurface numerical models have been refined and enhanced significantly in recent years and have improved our understanding of processes and dynamics. Numerical models are increasingly used to explore hypotheses and to develop new conceptual models of GW-SW interactions. New technologies like distributed temperature sensing (DTS) allow an assessment of process dynamics at unprecedented spatial and temporal resolution. These developments are reflected in the contributions to this Special Issue on GW-SW interactions. However, challenges remain in transferring process understanding across scales.     

Bedrock controls on the mineralogy and chemistry of PM<Subscript>10</Subscript> extracted from Australian desert sediments

Given the relevance of desert aerosols to environmental issues such as dust storms, climate change and human health effects, we provide a demonstration of how the bedrock geology of an arid area influences the mineralogy and geochemistry of even the finest particulate matter (i.e., the inhalable fraction <10 μm in size: PM₁₀). PM₁₀ samples extracted from desert sediments at geologically contrasting off-road sites in central and southeastern Australia (granitic, high grade metamorphic, quartzitic sandstone) were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The “granitic” PM₁₀ are highly alkali feldspathic and illitic, with a wide range of accessory minerals including rutile (TiO₂), monazite [(Ce, La, Nd, Th, Y) PO₄], xenotime (YPO₄), apatite [Ca₅(PO₄)₃ (F, OH, Cl)], hematite (Fe₃O₄), zircon (ZrSiO₄) and thorite (ThSiO₄). This mineralogy is reflected in the geochemistry which shows notable enrichments in rare earth elements (REE) and most high field strength elements (both held in the accessory minerals), and higher than normal levels of low (<2.0) ionic potential elements (Na, K, Li, Cs, Rb: held in alkali feldspar and illite). The “metamorphic” resuspended PM₁₀ define a mineralogy clearly influenced by local exposures of pelitic and calc-silicate schists (sillimanite, muscovite, calcite, Ca-amphibole), a dominance of monazite over other REE-bearing phases, and a geochemistry distinguished by enrichments in alkaline earth metals (Ca, Mg, Ba, Sr) and depletion in heavy REE. The “quartzite” PM₁₀, derived from rocks already recycled by Precambrian erosion and sedimentary transport, show a sedimentologically mature mineralogy of mostly quartz and kaolinite, detrital accessory ilmenite, rutile, monazite and hematite, and the strongest geochemical depletion (especially K, Rb, Cs, Na, Ca, Mg, Ba).     

Chemical and mineralogical characterisation of weathered historical bricks from the Venice lagoonal environment

Surficial and bulk samples of historical bricks of different age (from XII to XVIII centuries) recovered from a campaign of archaeological excavations recently carried out at the site of a medieval monastery in the S. Giacomo in Paludo Island in theVenice Lagoon have been characterised by FT-IR, TGA-DTG and DTA, XRD, SEM + EDS. The samples belong to a particular brick type commonly used in the Venice region: the "altinella brick". The bulk relative abundance of primary (i.e. calcite and dolomite) and secondary firing minerals (i.e. diopside and wollastonite) in the bricks coupled with their relative geometrical dimensions allows placing the samples in a chronological sequence according to known historical changes in brickmaking firing temperatures and practices. Most of the bricks were used as paving material and have been exposed to the action of seawater salts (chlorides and sulphates) due to periodical submersion following high tide episodes. Salt-laden (gypsum, halite, mirabilite) surficial patinas are indeed present but salt weathering does not appear to have affected the overall structural soundness of the bricks in this now abandoned island as it is the case with brickwork located in other more populated (and polluted) areas in Venice and its lagoon.