1,721,060 research outputs found
Radon groundwater monitoring at underground laboratories of Gran Sasso (Italy)
No full textAn automatic multiparametric equipment (groundwater temperature, electrical conductivity, pH. - Rn) has been planned and realized to study thee correlations between the variations of radon with the strain processes of the rock and transport properties related to the groundwater geochemistry. The monitoring activity at underground laboratories of Gran Sasso with a groundwater sampling period of twelve hours has been started from May 1996. From geochemical data recorded during the first year a high dynamic behaviour of shallow aquifer has been emphasized due to high permeability of the cretaceous limestones that form part of the Gran Sasso massif. Also, the residual time series analysis of the geochemical parameters has emphasised pre-co seismic in randon current in groundwater related to local seismicity
Liquid scintillation spectrometry at Gran Sasso National Laboratory: radiocarbon measurements
No full textRadiocarbon measurements using a QuantulusTM ultra low-level liquid scintillation spectrometer were performed
at the Gran Sasso National Laboratory (National Institute for Nuclear Physics) to study the efficiency and background
related to the measurement site (Plastino et al. 2001). Cosmic background and its variation have been removed in the Gran
Sasso laboratory by its 1400-m rock overburden. Stable, high-performance liquid scintillation counting conditions are
obtained when any remaining variable components of the environmental background, such as radon, are eliminated. The ultra
low-level liquid scintillation spectrometer Quantulus has an anti-Compton guard detector, which allows for the monitoring of
gamma radiation in the background. Guard detector efficiency in 14C background reduction is 8% at Gran Sasso, while 80%
is observed on the surface (Plastino and Kaihola 2004). The big difference in the guard detector efficiency between surface
laboratories and Gran Sasso is due to the absence of cosmic and associated lower energy Compton radiation (Plastino and
Kaihola 2006). The cosmic noise reduction observed at the Gran Sasso laboratory makes it possible to perform high-precision
14C measurements and to extend for these ideal samples the present maximum dating limit from 58,000 to 62,000 BP (5 mL,
3 days of counting) (Plastino et al. 2001)
Determination of the global coverage of the IMS xenon-133 component for the detection of nuclear explosions
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Diffusion in porous layers with memory
No full textThe process of diffusion of fluid in porous media and biological membranes has usually been modelled with Darcy's constitutive equation, which states that the flux is proportional to the pressure gradient. However, when the permeability of the matrix changes during the process, solution of the equations governing the diffusion presents severe analytical difficulties because the variation of permeability is not known a priori. A diverse formulation of the constitutive law of diffusion is therefore needed and many authors have studied this problem using various methods and solutions. In this paper Darcy's constitutive equation is modified with the introduction of a memory formalism. We have also modified the second constitutive equation of diffusion which relates the density variations in the fluid to the pressure, introducing rheology in the fluid represented by memory formalisms operating on pressure variations as well as on density variations. The memory formalisms are then specified as derivatives of fractional order, solving the problem in the case of a porous layer when constant pressures are applied to its sides. For technical reasons many studies of diffusion are devoted to the flux rather than to the pressure; in this work we shall devote our attention to studying the pressure and compute the Green's function of the pressure in the layer when a constant pressure is applied to the boundary (Case A) for which we have found closed-form formulae. The described problem has already been considered for a half space (Caputo 2000); however, the results for a half space are mostly qualitative since in most practical problems the diffusion occurs in layers. The solution is also readily extended to the case when a periodic pressure is applied to one of the boundary planes while on the other the pressure is constant (Case B) which mimics the effect of the tides on sea coasts. In this case we have found a skin effect for the flux which limits the flux to a surface layer whose thickness decreases with increasing frequency. Regarding the effect of pressure due to tidal waters on the coast, it has been observed that when the medium is sand and the fluid is water, for a sinusoidal pressure of 2x10(4) Pa and a period of 24 hr at one of the boundaries and zero pressure at the other boundary, the flux is sinusoidal with the same period and amplitude decaying exponentially with distance to become negligible at a distance of a few hundred metres. A brief discussion is given concerning the mode of determination of the parameters of memory formalisms governing the diffusion using the observed pressure at several frequencies. We shall also see that, as in the classic case of pure Darcy's law behaviour, the equation governing the flux resulting in the diffusion through porous media with memory is the same as that governing the pressure
Monitoring of geochemical and geophysical parameters in the Gran Sasso aquifer
No full textSince May 1996, groundwater monitoring (for 222Rn concentration, pH, electrical conductivity, pressure of dissolved
gases and temperature) has been carried out at the Gran Sasso National Laboratory of the National Institute of Nuclear
Physics using multiparametric equipment. This monitoring scheme has been designed with the aim to better define
the geophysical properties of the Gran Sasso aquifer and its radon source(s). The time series analyses show strong
anomalies in pH and radon concentrations, highly correlated with the known 1997–1998 Umbria–Marche seismic
sequence, which occurred in the central Apennines, Italy
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