Comparison of pumping at constant head and at a constant rate for determining the sustainable yield of a well     

Antonella Baiocchi  Francesca Lotti  Simone M. Piacentini  Vincenzo Piscopo 《Environmental Earth Sciences》2014,72(4):989-996

Determining the yield of a production well remains one of the main problems in hydrogeological studies. Starting from the results of a 3-year-long monitoring of a continuously exploited well functioning at constant head (i.e., at a variable discharge rate), a new pumping style has been examined using numerical models. The objective is to control the impact of pumping on the aquifer in accordance with the principle of sustainability. Different models were developed in a transient state and were calibrated using discharge data of the well during the recession periods. Successively, the trends of the residual outflow from the aquifer system with the well operating at variable discharge and at constant discharge were simulated. The results indicate that the ratio of the volume of water pumped from the well to the volume of residual outflow is a significant indicator of the sustainability of groundwater withdrawals. Modeling confirms that a constant discharge rate can be derived from the information gained through a preliminary production phase of a well at constant head. This approach appears to be particularly useful when the problem is determining the sustainable yield of a single well from aquifers with low hydraulic diffusivity.  相似文献   

Diffusion of Li in olivine. Part I: Experimental observations and a multi species diffusion model   总被引：3，自引：0，他引：3  

Ralf Dohmen  Simone A. Kasemann  Laurence Coogan 《Geochimica et cosmochimica acta》2010,74(1):274-5268

There are an increasing number of studies that focus on the systematics of the distribution of Li and its isotopes among different geochemical reservoirs. These studies have found that Li is relatively mobile compared to many other elements (e.g., Fe, Mg), and diffusion has been considered as a mechanism to generate large isotopic fractionations even at high temperatures. In order to quantify some of these aspects, we have measured Li diffusion rates experimentally along [0 0 1] of single crystals of olivines from San Carlos, Arizona and Pakistan, at 800-1200 °C at a total pressure of 100 kPa and fO₂ ≈ WM buffer. A complex diffusion behavior of Li is observed, indicating that two mechanisms of diffusion (a fast and a slower one) operate simultaneously. The behavior is well described by a model that partitions Li between two different sites in olivine - an octahedral site (Li_Me) and an interstitial site (Li_i). Transport of Li is a combination of hopping within and between each of these kinds of sites involving also vacancies on the octahedral site (V_Me). It is assumed that the homogeneous reaction (Li_Me = V_Me + Li_i) that maintains equilibrium distribution of Li between the sites is instantaneous compared to the timescales of all other processes associated with diffusive transport. One consequence of this mode of transport of Li in olivine is that the shape and length of diffusion profiles depend on the boundary conditions imposed at the surface of a crystal; i.e., the chemical environment (e.g., fO₂, aLi₄SiO₄), in addition to temperature and pressure. Our model describes the variable experimentally determined Li-profile shapes produced at different temperatures and with different boundary conditions, as well as their time evolution, quantitatively. Modeling the observed isotopic fractionation shows that ⁶Li diffuses about 5% faster than ⁷Li on the interstitial site. Inspection of published data on Li distribution in natural olivines that are available until now indicates that the fast (interstitial) mechanism of Li diffusion is unlikely to be dominant in most natural systems; Li rich, oxidizing environments (e.g., fluids?) may be exceptions. However, when it operates it can decouple the equilibration of Li isotopic gradients from the time scale of equilibration of overall Li concentrations. Diffusion dominated by the slower mechanism will occur on the average at a rate that is about an order of magnitude faster than diffusion of Fe, Mg and most other divalent cations in olivine; such diffusion of Li in olivine will be much slower than the rates of diffusion in clinopyroxene and plagioclase crystals at the same conditions. Fractionation of isotopes of Li by diffusion is likely to be a transient phenomenon and is more likely to be observed in crystals showing zoning of Li concentrations.  相似文献   

Cation partitioning versus temperature in (Mg0.70Fe0.23)Al1.97O4 synthetic spinel by in situ neutron powder diffraction     

A. Pavese  G. Artioli  U. Russo  A. Hoser 《Physics and Chemistry of Minerals》1999,26(3):242-250

Neutron powder diffraction experiments in the temperature range 300–1770 K were performed at BENSC, Berlin, Germany, on synthetic (Mg_0.70Fe_0.23) Al_1.97O₄. The cation partitioning over the crystallographic tetrahedral and octahedral sites was determined as a function of temperature through joint Rietveld refinements and advanced minimization techniques. The thermal expansion coefficients of the lattice parameter and inter-atomic bond lengths were also obtained from the full-profile structure refinements. The behaviour of the polyhedral bond-lengths, especially the T−O distances, and of the cell constant upon heating, clearly indicate that the interdiffusion of tetrahedral and octahedral Mg/Al cations starts at about 950 K. This result is straightforwardly supported by the direct analysis of the neutron site scattering factors: Fe always retains tetrahedral coordination at all temperatures, and the cation rearrangement is entirely due to Mg and Al diffusion. Received: 18 November 1997 / Revised, accepted: 23 August 1998  相似文献   

Jahn-Teller configurations in natural spinels     

V. Kuncser  U. Russo  R. Graziani  A. Della Giusta  P. Palade  M. Bulinski  G. Filoti 《Physics and Chemistry of Minerals》1999,27(2):95-102

The local configurations and related hyperfine interactions of the tetrahedrally coordinated Fe²⁺ in two natural spinels were investigated. A special fitting procedure of the Mössbauer spectra is proposed in order to cover the involved mechanisms over the whole temperature range. The behavior of the quadrupole splitting vs temperature was successfully explained in terms of the split of the electronic 3d ground state doublet under a non-cooperative Jahn-Teller effect also providing estimates of the splitting energy for each configuration.  相似文献   

Remotely sensed rivers in the Anthropocene: state of the art and prospects     

Hervé Piégay  Fanny Arnaud  Barbara Belletti  Mélanie Bertrand  Simone Bizzi  Patrice Carbonneau  Simon Dufour  Frédéric Liébault  Virginia Ruiz-Villanueva  Louise Slater 《地球表面变化过程与地形》2020,45(1):157-188

The rivers of the world are undergoing accelerated change in the Anthropocene, and need to be managed at much broader spatial and temporal scales than before. Fluvial remote sensing now offers a technical and methodological framework that can be deployed to monitor the processes at work and to assess the trajectories of rivers in the Anthropocene. In this paper, we review research investigating past, present and future fluvial corridor conditions and processes using remote sensing and we consider emerging challenges facing fluvial and riparian research. We introduce a suite of remote sensing methods designed to diagnose river changes at reach to regional scales. We then focus on identification of channel patterns and acting processes from satellite, airborne or ground acquisitions. These techniques range from grain scales to landform scales, and from real time scales to inter-annual scales. We discuss how remote sensing data can now be coupled to catchment scale models that simulate sediment transfer within connected river networks. We also consider future opportunities in terms of datasets and other resources which are likely to impact river management and monitoring at the global scale. We conclude with a summary of challenges and prospects for remotely sensed rivers in the Anthropocene. © 2019 John Wiley & Sons, Ltd.  相似文献   

Channelization of a large Alpine river: what is left of its original morphodynamics?          下载免费PDF全文

Vittoria Scorpio  Simone Zen  Walter Bertoldi  Nicola Surian  Marco Mastronunzio  Elena Dai Prá  Guido Zolezzi  Francesco Comiti 《地球表面变化过程与地形》2018,43(5):1044-1062

The Adige River drains 12 200 km² of the Eastern Alps and flows for 213 km within this mountain range. Similar to other large rivers in Central Europe, the Adige River was subject to massive channelization works during the 19th century. Thanks to the availability of several historical maps, this river represents a very valuable case study to document the extent to which the morphology of the river changed due to channelization and to understand how much is left of its original morphodynamics. The study was based on the analysis of seven sets of historical maps dating from 1803–1805 to 1915–1927, on geomorphological analysis, on the application of mathematical morphodynamic theories and on the application of bar and channel pattern prediction models. The study concerns 115 km of the main stem and 29 km of its tributaries. In the pre‐channelization conditions, the Adige River presented a prevalence of single‐thread channel planforms. Multi‐thread patterns developed only immediately downstream of the main confluences. During the 19th century, the Adige underwent considerable channel adjustment, consisting of channel narrowing, straightening, and reduction of bars and islands. Multi‐thread and single‐thread reaches evolved through different evolutionary trajectories, considering both the channel width and the bar/vegetation interaction. Bar and channel pattern predictors showed good correspondence with the observed patterns, including the development of multi‐thread morphologies downstream of the confluences. Application of the free‐bar predictor helped to interpret the strong reduction – almost complete loss – of exposed sediment bars after the channelization works, quantifying the riverbed inclination to form alternate bars. This morphological evolution can be observed in other Alpine rivers of similar size and similar massive channelization, therefore, a simplified conceptual model for large rivers subjected to channelization is proposed, showing that a relatively small difference in the engineered channel width may have a strong impact on the river dynamics, specifically on bar formation. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Archaeo-Geophysics Surveys in Pompeii     

D. Malfitana  G. Leucci  A. Mazzaglia  G. Cacciaguerra  L. De Giorgi  S. Barone  G. Fragalà  P. D. Pavone  S. Russo 《Surveys in Geophysics》2018,39(6):1219-1238

Within the extraordinary archaeological site of Pompeii, the Porta Nocera necropolis represents one of the most important sites with funerary monuments, burials and associated graves. The inherent informative potential of the archaeological/monumental heritage present in the Porta Nocera necropolis poses notable problems for the conservation and restoration of the structures and surfaces of the funerary monuments. Brought to light at different times during the second half of last century, they show signs of degradation caused by atmospheric agents and the rising level of the water table, which threatens the foundations. Other important monuments could be still buried. In order to verify both the state of preservation of the foundations of funerary buildings, the presence of still active causes of deterioration and the probable presence of other buried archaeological structures, integrated geophysical surveys, with ground penetrating radar (GPR), passive (Self Potential—SP) and active electrical resistivity tomography (ERT), were undertaken. Furthermore a three-dimensional model of the entire necropolis was created. This involved the creation of a specific survey methodology, combining laser scanning with ortho-photogrammetry using shots taken on the ground and from the air by the use of a drone. The integration of the acquired data allows us to plan future interventions of restoration.  相似文献   

Analysis of the primary and secondary microseisms in the wavefield of the ambient noise recorded in northern Poland     

Simone Lepore  Marek Grad 《Acta Geophysica》2018,66(5):915-929

Seasonal changes of the primary and secondary microseisms were analysed in the wavefield of the ambient noise recorded during the entire 2014 at the “13 BB star” array located in northern Poland, composed of thirteen, symmetrically arranged, broadband seismic stations. To that, spectral analysis, seismic interferometry, surface scalar wind speed distribution, and beamforming were used. Spectral analysis allowed to observe that a splitting of the secondary microseism peak was present in winter and autumn, and that the primary microseism peak was visible in spring, summer and autumn. Using seismic interferometry, the long-term characteristics of the noise wavefield were recognized. The seasonal variations of the secondary microseism source were described by means of the analysis of the surface scalar wind speed for each month. The splitting of the secondary peak was attributed to the interaction of a strong wind blowing from the North Sea with a weak wind blowing from the Baltic Sea. The seasonal variations of the primary microseism peak were characterized through the frequency-domain beamforming. The peak was identified during spring, summer and autumn, when the generated wavefield was coming from the Baltic Sea. The velocity of the wavefield was evaluated within the 2.0–5.0 km/s range. The described mechanism of generation of the microseisms, based on the interaction of the nearby winds, was found to be consistent with the models reported in the literature.  相似文献   

Numerical analysis of piled rafts     

G. Russo 《国际地质力学数值与分析法杂志》1998,22(6):477-493

An approximate numerical method for the analysis of piled raft foundations is presented. The raft is modelled as a thin plate and the piles as interacting non-linear springs. Both the raft and the piles are interacting with the soil which is modelled as an elastic layer. Two sources of non-linearity are accounted for: (i) the unilateral contact at the raft–soil interface and (ii) the non-linear load–settlement relationship of the piles. Both theoretical solutions and experimental results are used to verify that, despite the approximations involved, the proposed method of analysis can provide satisfactory solutions in both linear and non-linear range. © 1998 John Wiley & Sons, Ltd.  相似文献   

Chemo-mechanical behaviour of lightweight cemented soils     

Vitale  E.  Deneele  D.  Russo  G.  De Sarno  D.  Nicotera  M. V.  Papa  R.  Urciuoli  G. 《Acta Geotechnica》2020,15(4):933-945

Acta Geotechnica - In this paper, a multi-scale analysis of the effect of foam on chemo-mineralogical and microstructural features of the soil–cement–water system is presented....  相似文献