Point dilution tests to calculate groundwater velocity: an example in a porous aquifer in northeast Italy

Piccinini, Leonardo; Fabbri, Paolo; Pola, Marco

doi:10.1080/02626667.2015.1036756

Cited by 20 publications

(16 citation statements)

References 31 publications

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“…The resulting hydrogeological configuration of the VAP is a sequence of hydrofacies typical of a distal plain, with overlapping sequences of silty‐clayed aquitards and aquicludes and fine‐grained sandy aquifers. Overall, this sedimentological setting results in a multilayered aquifer system with different degrees of confinement (Fabbri et al, 2011, 2016; Fabbri & Piccinini, 2013; Piccinini et al, 2016, 2017; Vorlicek et al, 2004). Such multilayer systems formed by sequences of low‐ and high‐permeable layers (i.e., aquitards and aquifers) are commonly found in other alluvial aquifers with elevated As concentrations, such as the lower Mekong basin (e.g., Richards et al, 2019) or Red River Floodplain, Vietnam (e.g., Postma et al, 2007).…”

Section: Site Description and Initial Conceptual Modelmentioning

confidence: 99%

Conceptual Model of Arsenic Mobility in the Shallow Alluvial Aquifers Near Venice (Italy) Elucidated Through Machine Learning and Geochemical Modeling

Libera

Pedretti

Tateo

et al. 2020

Water Resources Research

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This work proposed a novel method to elucidate the controls of As mobility in complex aquifers based on an unsupervised machine learning algorithm, Self-Organizing Map (SOM), and process-based geochemical modeling. The approach is tested in the shallow aquifers of the Venetian Alluvial Plain (VAP) near Venice, Italy, where As concentrations seasonally and locally exceed recommended drinking water limits. SOM was fed using information from two geochemical surveys on eight VAP boreholes, and continuous reading of hourly groundwater head levels and weekly geochemical analyses from three VAP boreholes between mid-October 2017 and end of January 2018. The SOM analysis is consistent with redox-controlled dissolution-precipitation hydrous ferric oxides (HFOs) as a key control of As mobility in the aquifer. Dissolved As is positively correlated to Fe and NH þ 4 and negatively to the oxidizing-reducing potential (ORP). Negative correlation between As and groundwater head levels suggests a redox control by rainfall-driven recharge, which adds oxidants to the aquifer while progressively attenuating As. This mechanism is tested using process-based geochemical modeling, which simulates different transport modalities of oxidants entering the aquifer. Starting from reducing aquifer conditions, the model reproduces correctly the observed ORP and the trends in As and Fe, when the function describing the occurrence of oxidizing events scales according to the temporal occurrence of rainfall events. Heterogeneity can strongly control the local-scale effectiveness of recharge as a natural As attenuating factor, requiring a different model analysis to be properly assessed and to be developed in a follow-up study.

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Section: Site Description and Initial Conceptual Modelmentioning

confidence: 99%

Conceptual Model of Arsenic Mobility in the Shallow Alluvial Aquifers Near Venice (Italy) Elucidated Through Machine Learning and Geochemical Modeling

Libera

Pedretti

Tateo

et al. 2020

Water Resources Research

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“…(6), where m is the slope of the linear trend, which then allows the determination of v a with Eq. (7) (Piccinini et al 2016):…”

Section: Permeable Injection Bag Methodsmentioning

confidence: 99%

“…As an alternative to linear regression, apparent filtration velocities can also be determined using the CXTFIT code from the STANMOD software package (Šimůnek et al 1999). Piccinini et al (2016) showed, that the apparent filtration velocity can be determined by inversing the 1D advection-dispersion equation. However, instead of using concentration values normalized to C 1 , measured tracer concentrations were used as input values.…”

Section: Permeable Injection Bag Methodsmentioning

confidence: 99%

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Comparative application and optimization of different single-borehole dilution test techniques

2020

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Single-borehole dilution tests (SBDTs) are a method for characterizing groundwater monitoring wells and boreholes, and are based on the injection of a tracer into the saturated zone and the observation of concentration over depth and time. SBDTs are applicable in all aquifer types, but especially interesting in heterogeneous karst or fractured aquifers. Uniform injections aim at a homogeneous tracer concentration throughout the entire saturated length and provide information about inflow and outflow horizons. Also, in the absence of vertical flow, horizontal filtration velocities can be calculated. The most common method for uniform injections uses a hosepipe to inject the tracer. This report introduces a simplified method that uses a permeable injection bag (PIB) to achieve a close-to-uniform tracer distribution within the saturated zone. To evaluate the new method and to identify advantages and disadvantages, several tests have been carried out, in the laboratory and in multiple groundwater monitoring wells in the field. Reproducibility of the PIB method was assessed through repeated tests, on the basis of the temporal development of salt amount and calculated apparent filtration velocities. Apparent filtration velocities were calculated using linear regression as well as by inverting the one-dimensional (1D) advection-dispersion equation using CXTFIT. The results show that uniform-injection SBDTs with the PIB method produce valuable and reproducible outcomes and contribute to the understanding of groundwater monitoring wells and the respective aquifer. Also, compared to the hosepipe method, the new injection method requires less equipment and less effort, and is especially useful for deep boreholes.

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“…These fine sediments often contain peat layers formed in a floodplain environment, with a thickness of decimeters and a lateral extension of kilometers. The Drainage Basin to the Venice Lagoon (DBVL) extends to the lower plain environment, alternating silty layers with low permeability and sandy permeable layers, where the primary aquifers are located (Cambruzzi et al, 2009;Dal Prà et al, 1992;Fabbri and Piccinini, 2013;Fabbri et al, 2011Fabbri et al, , 2016Piccinini et al, 2015Piccinini et al, , 2016Vorlicek et al, 2004) (Fig. 1C).…”

Section: Geological and Hydrogeological Settingsmentioning

confidence: 96%

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

Libera

Fabbri

Mason³

et al. 2017

Science of The Total Environment

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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 hydro-geochemically 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 approach was applied exploiting the geochemical relationships among As, Fe and NH4+. The obtained spatial predictions of arsenic concentrations were 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.

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Point dilution tests to calculate groundwater velocity: an example in a porous aquifer in northeast Italy

Cited by 20 publications

References 31 publications

Conceptual Model of Arsenic Mobility in the Shallow Alluvial Aquifers Near Venice (Italy) Elucidated Through Machine Learning and Geochemical Modeling

Conceptual Model of Arsenic Mobility in the Shallow Alluvial Aquifers Near Venice (Italy) Elucidated Through Machine Learning and Geochemical Modeling

Comparative application and optimization of different single-borehole dilution test techniques

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

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