An example of aquifer heterogeneity simulation to modeling well-head protection areas

Groundwater management requires the definition of Well-Head Protection Areas (WHPA) for water supply wells. Italian law uses geometrical, chronological and hydrogeological criteria for WHPA identification, providing a groundwater travel time of 60 days for the definition of the Zone of Travel (ZOT). An exhaustive ZOT delineation must involve numerical modeling of groundwater flow together with simulation of the advective component of the transport process. In this context, the spatial variability of hydrogeological and transport parameters has to be critically estimated during numerical modeling implementation. In the present article, geostatistical simulation using a transition probability approach and groundwater numerical modeling were performed to delineate WHPAs for several supply wells in the middle Venetian Plain, taking into account the lithologic heterogeneity of the aquifer. The transition probability approach for the lithologic data was developed by T-PROGS software, while MODDLOW-2005 and PEST-ASP were used, respectively, to reproduce and calibrate site-specific hydraulic head data. Finally, a backward particle tracking analysis was performed with MODPATH to outline the 60-day ZOT

Assessing transmissivity from specific capacity in an alluvial aquifer in the middle Venetian plain (NE Italy)

Defining aquifer permeability distribution accurately over large areas is often debated in hydrogeology. The operational efforts to calculate hydraulic conductivity with classical aquifer tests are significant; however, accurate knowledge of permeability areal distribution is fundamental both from a hydrogeological and a modeling standpoint. This paper presents an empirical relationship between the transmissivity (T) and the specific capacity (SC) values obtained from experimental aquifer and well tests. All experimental values were obtained from 50 mm wells in middle Venetian plain artesian gravel aquifers. Many other authors have presented empirical relationships between T and SC, but most are related to fissured/karst aquifers, and only a few concern alluvial porous aquifers. Analysis of the T vs. SC relationship standardized residuals shows that a linear relationship produces statistically significant normal residuals compared with an exponential relationship

Geostatistics as a tool to improve the natural background level definition: An application in groundwater

The Natural Background Level (NBL), suggested by UE BRIDGE project, is suited for spatially distributed datasets providing a regional value that could be higher than the Threshold Value (TV) set by every country. In hydrogeochemically dis-homogeneous areas, the use of a unique regional NBL, higher than TV, could arise problems to distinguish between natural occurrences and anthropogenic contaminant sources. Hence, the goal of this study is to improve the NBL definition employing a geostatistical approach, which reconstructs the contaminant spatial structure accounting geochemical and hydrogeological relationships. This integrated mapping is fundamental to evaluate the contaminant's distribution impact on the NBL, giving indications to improve it. We decided to test this method on the Drainage Basin of Venice Lagoon (DBVL, NE Italy), where the existing NBL is seven times higher than the TV. This area is notoriously affected by naturally occurring arsenic contamination. An available geochemical dataset collected by 50 piezometers was used to reconstruct the spatial distribution of arsenic in the densely populated area of the DBVL. A cokriging approachwas applied exploiting the geochemical relationships among As, Fe andNH4+. The obtained spatial predictions of arsenic concentrationswere divided into three different zones: i) areas with an As concentration lower than the TV, ii) areas with an As concentration between the TV and the median of the values higher than the TV, and iii) areas with an As concentration higher than the median. Following the BRIDGE suggestions, where enough samples were available, the 90th percentile for each zone was calculated to obtain a local NBL (LNBL). Differently from the original NBL, this local value gives more detailed water quality information accounting the hydrogeological and geochemical setting, and contaminant spatial variation. Hence, the LNBL could give more indications about the distinction between natural occurrence and anthropogenic contamination

Neutral current Drell-Yan with combined QCD and electroweak corrections in the POWHEG BOX

Following recent work on the combination of electroweak and strong radiative corrections to single W-boson hadroproduction in the POWHEG BOX framework, we generalize the above treatment to cover the neutral current Drell-Yan process. According to the POWHEG method, we combine both the next-to-leading order (NLO) electroweak and QED multiple photon corrections with the native NLO and Parton Shower QCD contributions. We show comparisons with the predictions of the electroweak generator HORACE, to validate the reliability and accuracy of the approach. We also present phenomenological results obtained with the new tool for physics studies at the LHC.Comment: 10 pages, 14 figures, 1 table. One new figure, some plots with updated results, added text. Final version to appear in EPJ

W gamma production in hadronic collisions using the POWHEG+MiNLO method

We detail a calculation of W gamma production in hadronic collision, at Next-to-Leading Order (NLO) QCD interfaced to a shower generator according to the POWHEG prescription supplemented with the MiNLO procedure. The fixed order result is matched to an interleaved QCD+QED parton shower, in such a way that the contribution arising from hadron fragmentation into photons is fully modeled. In general, our calculation illustrates a new approach to the fully exclusive simulation of prompt photon production processes accurate at the NLO level in QCD. We compare our predictions to those of the NLO program MCFM, which treats the fragmentation contribution in terms of photon fragmentation functions. We also perform comparisons to available LHC data at 7 TeV, for which we observe good agreement, and provide phenomenological results for physics studies of the W gamma production process at the Run II of the LHC. The new tool, which includes W leptonic decays and the contribution of anomalous gauge couplings, allows a fully exclusive, hadron-level description of the W gamma process, and is publicly available at the repository of the POWHEG BOX. Our approach can be easily adapted to deal with other relevant isolated photon production processes in hadronic collisions.Comment: 38 pages, 5 Tables, 9 Figures. Final version published in JHEP. Acknowledgments to Galileo Galilei Institute for Theoretical Physics and to INFN adde

Conceptual and numerical models of a tectonically-controlled geothermal system: a case study of the Euganean Geothermal System, Northern Italy

The Euganean Geothermal Field (EGF) is the most important thermal field in northern Italy. It is located in the alluvial plain of the Veneto Region where approximately 17*106 m3 of thermal water with temperatures of 60–86 °C are exploited annually. A regional-scale conceptual model of the Euganean Geothermal System is proposed in this paper using the available hydrogeologic, geochemical and structural data for both the EGF and central Veneto. The thermal water is of meteoric origin and infiltrates approximately 80 km to the north of the EGF in the Veneto Prealps. The water flows to the south in a Mesozoic limestone and dolomite reservoir reaching a depth of approximately 3,000 m and a temperature of approximately 100 °C due to the normal geothermal gradient. The regional Schio-Vicenza fault system and its highly permeable damage zone act as a preferential path for fluid migration in the subsurface. In the EGF area, a geologic structure formed by the interaction of different segments of the fault system increases the local fracturing and the permeability favoring the upwelling of the thermal waters. Numerical simulations are performed to validate the proposed conceptual model using a finite difference code that simulates thermal energy transport in hydrothermal systems. A specific configuration of thermal conductivity and permeability for the formations involved in the thermal system is obtained after calibration of these parameters. This set of parameters is verified in a long-term simulation (55,100 years) obtaining a 60–70 °C plume in the EGF area. The modeled temperatures approach the measured temperatures of 60–86 °C, demonstrating that this conceptual model can be realistically simulated

Noisy quantum walks of two indistinguishable interacting particles

We investigate the dynamics of continuous-time two-particle quantum walks on a one-dimensional noisy lattice. Depending on the initial condition, we show how the interplay between particle indistinguishability and interaction determines distinct propagation regimes. A realistic model for the environment is considered by introducing non-Gaussian noise as time-dependent fluctuations of the tunneling amplitudes between adjacent sites. We observe that the combined effect of particle interaction and fast noise (weak coupling with the environment) provides a faster propagation compared to the noiseless case. This effect can be understood in terms of the band structure of the Hubbard model, and a detailed analysis as a function of both noise and system parameters is presented.Comment: 9 pages, 8 figure