Groundwater flow and geochemical modeling of the Acque Albule thermal basin (Central Italy): a conceptual model for evaluating influences of human exploitation on flowpath and thermal resource availability

Although the Acque Albule Basin has been studied since the middle of the 19th century, a comprehensive geologic conceptual model of the area has not yet been developed. The natural setting has been heavily modified by anthropic activities. Rapid evolution during the last 25 years has caused many interferences, which have led to a drastic increase of the hazards and linked risks, mainly related to water resource overexploitation and subsidence. The implementation of an exhaustive framework has become mandatory for environmental and management purposes. Starting from a critical review of previous studies, hydrogeologic and hydrogeochemical surveys and related numerical modeling have been carried out in order to achieve a quantitative understanding of the active phenomena and processes. Several hydrogeologic issues have been addressed concerning aquifer recharge areas and the different flowpaths of groundwater in respect to their division into a shallow and a deep circuit. Account has been taken of the groundwater chemistry as a function of water—rock interactions and mixing processes with uprising fluids. Different scenarios of groundwater flow in the Acque Albule aquifer have been built, using previously available piezometric measurements and the hydrodynamic parameters determined by in situ tests. These results led to the formulation of an updated hydrogeologic conceptual model to be further implemented, in which past, present and future anthropic instances and the potential of natural resources of the area have been included and taken into account. A sound conceptual model must rely on the design and development of a logical geo-database in which information is stored, updated and processed. This operational framework can result in a useful tool for land management, surveys planning and design, hazard and risk evaluation, identification of best practices and economic development of the area

Effect of hydraulic retention time on the electro-bioremediation of nitrate in saline groundwater

Bioelectrochemical systems (BES) have proven their capability to treat nitrate-contaminated saline groundwater and simultaneously recover value-added chemicals (such as disinfection products) within a circular economy-based approach. In this study, the effect of the hydraulic retention time (HRT) on nitrate and salinity removal, as well as on free chlorine production, was investigated in a 3-compartment BES working in galvanostatic mode with the perspective of process intensification and future scale-up. Reducing the HRT from 30.1 +/- 2.3 to 2.4 +/- 0.2 h led to a corresponding increase in nitrate removal rates (from 17 +/- 1 up to 131 +/- 1 mgNO3--N L-1d-1), although a progressive decrease in desalination efficiency (from 77 +/- 13 to 12 +/- 2 %) was observed. Nitrate concentration and salinity close to threshold limits indicated by the World Health Organization for drinking water, as well as significant chlorine production were achieved with an HRT of 4.9 +/- 0.4 h. At such HRT, specific energy consumption was low (6.8 center dot 10-2 +/- 0.3 center dot 10-2 kWh g-1NO3--Nremoved), considering that the supplied energy supports three processes simultaneously. A logarithmic equation correlated well with nitrate removal rates at the applied HRTs and may be used to predict BES behaviour with different HRTs. The bacterial community of the bio-cathode under galvanostatic mode was dominated by a few populations, including the genera Rhizobium, Bosea, Fontibacter and Gordonia. The results provide useful information for the scale-up of BES treating multi-contaminated groundwater

Interazione tra acquifero superficiale e profondo nella Piana di Tivoli (Roma): Approccio multi-isotopico e modello numerico geochimico

Interaction between shallow and deep groundwater flow systems has been investigated in the Tivoli Plain aquifer system (Rome, Central Italy). During the last decade an intense activity in the travertine quarries in the Acque Albule Basin has caused a significant drop in the water table of the shallow travertine aquifer. As a consequence, subsidence and high instability risk are affecting buildings in this area constructed on top of Holocene sediments composed of mainly silty clay with high level of organic content, which are underlying by travertine deposits. A multi-isotope approach was used to have a better understanding of interactions between shallow and deep aquifers and to improve the knowledge of the hydrogeological conceptual model, which has implication for groundwater management in the Tivoli plain. Environmental isotopes are largely used for investigation of water origin, residence time and flowpaths (Kendall et al., 1998; Coplen et al., 1999). They are also useful for a better understanding of chemical reactions during water-rock interaction. A combined hydrogeologic and isotopic investigation using chemical and isotopic tracers such as SO4/Cl, δ18O, δ 2H, 87Sr/86Sr, δ34S, and δ13C was carried out in order to determine the sources of water recharge to the aquifer, the origin of solutes, and the mixing processes, in the Tivoli Plain, a Quaternary basin filled by travertines (Faccenna et al., 2008). The study area is located 30 km East of Rome. The recharge areas for the shallow groundwater in the travertine aquifer are supposed to be the carbonate ridges of Lucretili and Tiburtini mountains (Capelli et al., 2005: Petitta et al., 2010). The travertine aquifer also receives a contribution of mineralized fluids from a deep aquifer contained in the buried meso-cenozoic carbonates, which are separated from the shallow aquifer by low-permeability volcanic and clayed deposits. Representative samples of the water cycle in Tivoli Plain, which included springs, lakes, deep groundwater and water from the quarries were sampled for chemical and isotope analysis. Base-flow springs are generally saturated or oversaturated with respect to calcite, which explains the travertine formation (Minissale et al., 2002). A large number of samples including groundwater and surface water were collected in the Acque Albule Basin, while other samples come from the recharge area (S4, S5, S6, P6) (Fig. 3.2). S2 is a spring located out of the Basin, which is directly fed by a deep contribution from buried carbonate bedrock. Major ion chemistry data showed a groundwater stratification in the travertine aquifer, associated with mixing of the shallow groundwater with discharge mineralized fluids from the deep aquifer, partially enhanced by increasing pumping in the quarries. Results indicate that the hydrochemistry of groundwater in Tivoli Plain and adjacent recharge areas is characterized by a mixing among three end-members: A. groundwater of recharge area, B. groundwater of the shallow travertine aquifer (Acque Albule Basin), C. groundwater of deep carbonate aquifer. The end-members are represented by three different geochemical facies: Facies A: Ca – HCO3 type groundwater: TDS (0-0,8 g L-1); SO4 (0-250 mg L-1); DIC (0-7 mmol kg-1); EC (0-2 mS cm-1). Facies B: Ca – HCO3–SO4 type groundwater: TDS (0,8-2,4 g L-1); SO4 (250-800 mg L-1); DIC (7-16 mmol kg-1); EC (2-3,5 mS cm-1). Facies C: Ca-Mg – HCO3-SO4 type groundwater: TDS (2,4-3,6 g L-1); SO4 (800-1200 mg L-1); DIC (16-18 mmol kg-1); EC (3,5-4,5 mS cm-1). A multi-isotope approach (18O, 2H in water, 34S and 18O in sulphate, 13C in DIC and 87Sr/86Sr ratios) has been adopted in the study to obtain a better understanding of interactions between shallow and deep groundwater. The stable isotope data, collected in rain stations at different altitude and in groundwater, suggest the existence of different flowpaths and mixing of shallow groundwater associated with recharge in the Tivoli Plain. Based on seasonal changes in 18O and 2H, the recharge contribution coming from the carbonate ridges to deep groundwater has also been documented. The 13C data in DIC show a wide range in 13C values that varies between -12.3‰ and +8.6‰. The more depleted 13C values are considered representatives of the recharge area, where a input of soil CO2 occurs during rainfall infiltration mixing with DIC from dissolution of carbonates. Samples from Acque Albule Basin show values between +0.4‰ and +8.6‰, where an input of 13C enriched CO2 is associated with a deep contribution of hydrothermal fluids from the buried carbonate aquifer. The correlations in chapter 4 show two separated sources for DIC in the water samples, with some samples (P5, S6, C4) placed in intermediate position, justified by the influence by mixing processes. The 34S and 18O data in sulphate also highlight the existence of two different sources for dissolved sulphates: the groundwater collected in Acque Albule Basin have sulphates which can be associated to the Triassic evaporites of the deep aquifer; otherwise, sulphates of secondary origin from the shallow aquifer characterize samples collected in the recharge area. The positive values of 34S (> 10‰) may exclude sulphate reduction as main process in sulphate contribution, especially because it could not explain the high sulphate concentration of the B-C facies. A possible relationship between dissolved sulphates and the occurrence of H2S uprising fluids in the shallow aquifer can be discarded. Finally, the 87Sr/86Sr data with values ranging between 0,7076 and 0,7082 confirm that the contribution of dissolved solutes is associated with two sources: marine carbonates from the deep aquifer (groundwater influenced by deep flowpaths); continental and volcanic deposits in case of the shallow aquifer (groundwater having not interaction with deep flowpaths). An Inverse Model carried out with Phreeqc 2.16 by Parkhurst & Appelo (1999) has developed a theoretical geochemical evolution with water-rock interaction processes. According to an inverse mixing model, it is possible to conclude that both dissolution/precipitation and ion exchange processes are the key of geochemical evolution along groundwater flowpath, confirmed also by the calculated mixing between deep and shallow aquifers. The chemical and isotope tracers provided information for distinguishing different sources of dissolved salts and different groundwater circulation in the Tivoli Plain. The results of this study have improved the hydrogeological conceptual model, which can be summarized as follows: • the Ca-HCO3 groundwater type represents a flow system fed directly by meteoric water in carbonate ridges of Lucretili and Tiburtini mountains, surrounding the Tivoli Plain. The flow system is subdivided in a shallower one, that fills directly the travertine aquifer of the Acque Albule Basin, and in a deeper one, circulating in the buried carbonate bedrock; • the Ca-Mg–HCO3-SO4 groundwater type represents a deeper circulation having a contribution of high salinity fluids, uprising from the deep carbonate aquifer, probably related to the Colli Albani volcanic district. Mixing processes, which characterize the travertine shallow aquifer have been recognized in several water samples, especially inside the quarries area. In this area the mixing between the two components is widely enhanced by the recent occurrence of intense pumping activity (Prestininzi, 2008). The chemistry of samples in this area corresponds to a Ca–HCO3–SO4 groundwater type. Deep saline fluids rise and mix with recharge water in the shallow aquifer, evolving across dissolution/precipitation and ion exchange processes. The 18O, 2H and 87Sr/86Sr isotope values confirmed the meteoric origin of the groundwater and the different flowpaths influencing the hydrochemistry composition of groundwater in Tivoli Plain. The existence of two different sources of groundwater is supported by the results of 34S data in sulphates and 13C data in DIC. Both these two tracers support the existence of mixing in the shallow aquifer, showing intermediate values in the samples which are characterized by relative lower salinity

Interaction between shallow and deep aquifers in the Tivoli Plain (Central Italy) enhanced by groundwater extraction: A multi-isotope approach and geochemical modeling

In the Tivoli Plain (Rome, Central Italy) the interaction between shallow and deep groundwater flow systems enhanced by groundwater extraction has been investigated using isotopic and chemical tracers. A conceptual model of the groundwater flowpaths has been developed and verified by geochemical modeling. A combined hydrogeochemical and isotopic investigation using ion relationships such as DIC/Cl , Ca/(Ca + Mg)/SO4/(SO4 + HCO3), and environmental isotopes (delta O-18, delta H-2, Sr-87/Sr-86, delta S-34 and delta C-13) was carried out in order to determine the sources of recharge of the aquifer, the origin of solutes and the mixing processes in groundwater of Tivoli Plain. Multivariate statistical methods such as principal component analysis and Cluster analyses have confirmed the existence of different geochemical facies and the role of mixing in the chemical composition of the groundwater. Results indicate that the hydrochemistry of groundwater is characterized by mixing between end-members coming directly from carbonate recharge areas and to groundwater circulating in a deeply buried Meso-Cenozoic carbonate sequence. The travertine aquifer is fed by both flow systems, but a local contribution by direct input in the Plain has also been recognized. The stable isotope data (O-18, H-2, C-13 and S-34) supports the flow system conceptual model inferred from the geochemical data and represents key data to quantify the geochemical mixing in the different groundwaters of the Plain. The results of numerical modeling (PHREEQC) are consistent with the flowpaths derived from the hydrogeochemical conceptual model. The inverse models performed generated the main geochemical processes occurring in the groundwater flow system, which also included mixing. Geochemical and isotope modeling demonstrate an increasing influence of groundwater from the deeply buried aquifer in the travertine aquifer, enhanced by lowering of the travertine aquifer water table due to quarry pumping. (C) 2011 Elsevier Ltd. All rights reserved

Multi-chemical and isotope approach for studying shallow and deep groundwater interaction in an urban area: The case of Tivoli Plain (central Italy)

Interaction between shallow and deep groundwater flow systems has been investigated by the means of chemical and isotopic tracers in the Tivoli Plain aquifer system (Rome, central Italy). During the last decade an intense activity in the travertine quarries in the Acque Albule basin has caused a significant drop in the water table of the shallow travertine aquifer. A multi-isotope approach was used to have a better understanding of interactions between shallow and deep aquifers, and to improve the knowledge of the conceptual hydrogeological model, which has implications for groundwater management in the Tivoli plain. The hydrochemistry of the travertine aquifer is characterized by a mixing between two end-members related, respectively, to groundwater coming directly from outcropping carbonate aquifers and to groundwater circulating in deep buried Meso-Cenozoic carbonate sequences. 18O and l3C isotope tracers are diagnostic for the geochemical mixing definition. Copyright © 2011 IAHS Press

A new approach for the assessment of sleepiness and predictivity of obstructive sleep apnea in drivers: A pilot study

Background: Falling asleep behind the wheel is one of the most relevant consequences of obstructive sleep apnea (OSA). We created a new screening questionnaire, named the Driver Sleepiness Score (DSS), aiming to assess sleepiness in drivers with suspected OSA. The primary aim of our study was to evaluate sleepiness in drivers with a suspicion of OSA by the DSS in order to assess its correlation with the apnea-hypopnea index (AHI), oxygen desaturation index (ODI), and total sleep time with oxyhemoglobin saturation below 90% (TST90). We also aimed to assess the diagnostic accuracy of DSS for three different cutoffs of AHI (AHI = 5, AHI = 15, AHI = 30), which allow stratification of the severity of OSA. Materials and Methods: Seventy-three driving patients at risk for OSA participated in the study. DSS and the Epworth Sleepiness Scale (ESS) were both administered in operator-dependent modality and in randomized sequence. Results: The DSS showed higher accuracy in screening patients with mild OSA [area under curve (AUC): 0.88 vs 0.74] and moderate OSA (AUC: 0.88 vs 0.79), whereas ESS showed higher accuracy in screening patients with severe OSA (AUC: 0.91 vs 0.78). A DSS score ≥ 7 is the optimal cutoff for distinguishing true positives from false positives for the presence of OSA and for its different severity levels. The administration of both questionnaires increases the accuracy for the detection of all OSA severity levels. Conclusions: If validated, DSS may qualify as a new screening tool specifically for drivers with the suspicion of having OSA, in combination with the ESS