Special Issue "Applying Artificial and Environmental Tracing Techniques in Hydrogeology"

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Hydrology and Hydrogeology".

Deadline for manuscript submissions: 31 July 2021.

Special Issue Editors

Dr. Federico Cervi
E-Mail Website
Guest Editor
Via Maccagnano, Reggio Emilia, Italy
Interests: hydrogeology; hydrochemistry; tracers; isotopes; fractured and porous media; groundwater
Special Issues and Collections in MDPI journals
Prof. Dr. Alberto Tazioli
E-Mail Website
Guest Editor
Department of Science and Matter Engineering, Environment and Urban Planning (SIMAU), Marche Polytechnic University, Via Brecce Bianche 12, 60131 Ancona, Italy
Interests: hydrogeology; hydrology; geomorphology; tracer; fractured rocks; isotope hydrology

Special Issue Information

Dear Colleagues,

Over the last decades, the use of tracers in groundwater sciences has abruptly increased, demonstrating their important usefulness in solving hydrogeological problems at different spatial and time scales. They are used in laboratory experiments (column tests) and field investigations (even at catchments and regional scales), and deal with water, lasting from few minutes to many millennia. They are recognized as powerful tools for obtaining information that cannot be gained by any other conventional means, such as depicting groundwater flow-paths and mixing processes among different end-members, identifying a connection between surficial water and groundwater, estimating the recharge areas of infiltrative water, and quantifying pre-infiltrative evaporative processes and groundwater residence times.

To date, many artificial (i.e., intentionally introduced into the hydrogeological system, such as dyes) and environmental (i.e., entering as a part of the hydrological cycle, like water isotopes) tracer have been tested, and the specific choice of a suitable one (or a subset of them; multi-tracing techniques) strictly depends on which hydrogeological investigation is to be done.

The aims of this Special Issue are to provide a current overview of the different tracer techniques in hydrogeology. We are particularly interested to case studies involving environmental and/or artificial tracers that demonstrate the capability of such methods in hydrogeological studies from mountainous and lowlands areas, in presence of fractured, karstic, and porous aquifers. Preference will be given to studies that are based on some selected artificial dyes (both in the form of solutes and particles, namely dissolved salts and ions, fluorescent dyes, synthetic DNA, and microspheres) and environmental tracers (pharmaceuticals and other synthetic compounds, and stable and radioactive isotopes).

We warmly invite authors to submit papers on the following areas, as well as on related broad topics:

  • Groundwater–surface water interaction
  • Recharge areas estimates
  • Groundwater dating
  • Groundwater pollution
  • Water resources management

Dr. Federico Cervi
Prof. Dr. Alberto Tazioli
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Water is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • tracer
  • hydrogeology
  • groundwater
  • isotope
  • mean residence time
  • dating
  • pollution

Published Papers (8 papers)

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Research

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Article
The Role of Faults in Groundwater Circulation before and after Seismic Events: Insights from Tracers, Water Isotopes and Geochemistry
Water 2021, 13(11), 1499; https://doi.org/10.3390/w13111499 - 27 May 2021
Viewed by 466
Abstract
The interaction between fluids and tectonic structures such as fault systems is a much-discussed issue. Many scientific works are aimed at understanding what the role of fault systems in the displacement of deep fluids is, by investigating the interaction between the upper mantle, [...] Read more.
The interaction between fluids and tectonic structures such as fault systems is a much-discussed issue. Many scientific works are aimed at understanding what the role of fault systems in the displacement of deep fluids is, by investigating the interaction between the upper mantle, the lower crustal portion and the upraising of gasses carried by liquids. Many other scientific works try to explore the interaction between the recharge processes, i.e., precipitation, and the fault zones, aiming to recognize the function of the abovementioned structures and their capability to direct groundwater flow towards preferential drainage areas. Understanding the role of faults in the recharge processes of punctual and linear springs, meant as gaining streams, is a key point in hydrogeology, as it is known that faults can act either as flow barriers or as preferential flow paths. In this work an investigation of a fault system located in the Nera River catchment (Italy), based on geo-structural investigations, tracer tests, geochemical and isotopic recharge modelling, allows to identify the role of the normal fault system before and after the 2016–2017 central Italy seismic sequence (Mmax = 6.5). The outcome was achieved by an integrated approach consisting of a structural geology field work, combined with GIS-based analysis, and of a hydrogeological investigation based on artificial tracer tests and geochemical and isotopic analyses. Full article
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Article
Phosphorus Transport in a Lowland Stream Derived from a Tracer Test with 32P
Water 2021, 13(8), 1030; https://doi.org/10.3390/w13081030 - 09 Apr 2021
Viewed by 336
Abstract
Small streams in urbanized rural areas receive loads of P from various, often episodic, sources. This paper addresses, through a tracer test with 32P, retention and transport of a pulse input of phosphorus in a 2.6 km long stretch of a channelized second-order lowland stream. Tritiated water was introduced alongside the 32P-labelled ortophosphate in order to isolate the influence of the hydrodynamic factors on P behavior. Tracer concentrations in unfiltered water samples were measured by liquid scintillation counting. Four in-stream and five hyporheic breakthrough curves were collected at four points along the stream, two of which encompass a beaver dam impoundment. The overall retention efficiency of 32P along the studied reach was 46%. The transient storage transport model OTIS-P provided reasonable fits for in-stream breakthrough curves (BTCs) but failed at reproducing the hyporheic BTCs. The overall small effect of transient storage on solute transport was higher in the stretch with a more pronounced surface storage. Transient storage and phosphorus retention were not enhanced in the beaver dam impoundment. Full article
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Article
Modified Convergent Flow Tracing Method for Evaluating Advective Velocity and Effective Porosity in Fractured Rock Aquifers
Water 2020, 12(12), 3565; https://doi.org/10.3390/w12123565 - 18 Dec 2020
Viewed by 632
Abstract
This study presented the analysis of the modified convergent flow tracing method, which is a modified virtual solute transport approach to retrieve tracer masses from a pulse image (virtual) well to an extraction well. In the convergent flow tracer test, approximate analytical solutions [...] Read more.
This study presented the analysis of the modified convergent flow tracing method, which is a modified virtual solute transport approach to retrieve tracer masses from a pulse image (virtual) well to an extraction well. In the convergent flow tracer test, approximate analytical solutions were extended for the pulse image well using a single-well tracing method. This method transformed the drift-and-pumpback conditions of the single-well tracing method. The method requires a prior information of the effective porosity. Using sodium chloride as a tracer mass, the tracer data sampled through field-scale tests were used to obtain breakthrough curves. This modified method was different from the pre-existing single method because it considers both the ambient groundwater movement (the two classes of drifts) and the constant volumetric flow rate during the pumping phase. The method was applied to the tracer test at underground research tunnel for verifying the theory inductively derived from the single tracing method. Through field tests, the values of velocity and porosity were compared to the results of the drift-and-pumpback equations of the single-well test, and the several different equations related to breakthrough curves of the two-well tests conducted on a field scale. Full article
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Article
Comparison between Periodic Tracer Tests and Time-Series Analysis to Assess Mid- and Long-Term Recharge Model Changes Due to Multiple Strong Seismic Events in Carbonate Aquifers
Water 2020, 12(11), 3073; https://doi.org/10.3390/w12113073 - 02 Nov 2020
Cited by 3 | Viewed by 738
Abstract
Understanding the groundwater flow in carbonate aquifers represents a challenging aspect in hydrogeology, especially when they have been struck by strong seismic events. It has been proved that large earthquakes change springs hydrodynamic behaviour showing transitory or long-lasting variations and making their management [...] Read more.
Understanding the groundwater flow in carbonate aquifers represents a challenging aspect in hydrogeology, especially when they have been struck by strong seismic events. It has been proved that large earthquakes change springs hydrodynamic behaviour showing transitory or long-lasting variations and making their management much more difficult. This is the case of Sibillini Massif (central Italy), which has been hit by the well-known 2016–2017 seismic period. This work aims to improve the knowledge of carbonate aquifers groundwater circulation and their possible changes in the hydrodynamic behaviour, during and after a series of strong seismic events. The goal has been achieved by comparing long-time tracer tests and transient time-series analysis, based on a sliding-window approach. This approach allowed investigating transient variations in the carbonate aquifers recharge system, highlighting the changes of relationships between the inflow contributions to the spring discharge in the area. As a result, the seismically triggered pore pressure distribution, and the hydraulic conductivity variations, because of the ground shaking and the fault systems activation, account for all the mid- and long-term modifications in the recharge system of Sibillini aquifers, respectively. These outcomes provide valuable insights to the knowledge of aquifer response under similar hydrogeological conditions, that are vital for water management. Full article
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Article
The Role of Snowmelt on the Spatio-Temporal Variability of Spring Recharge in a Dolomitic Mountain Group, Italian Alps
Water 2020, 12(8), 2256; https://doi.org/10.3390/w12082256 - 11 Aug 2020
Cited by 4 | Viewed by 1165
Abstract
Springs play a key role in the hydrology of mountain catchments and their water supply has a considerable impact on regional livelihood, biodiversity, tourism, and power generation. However, there is still limited knowledge of how rain and snow contribute to the recharge of [...] Read more.
Springs play a key role in the hydrology of mountain catchments and their water supply has a considerable impact on regional livelihood, biodiversity, tourism, and power generation. However, there is still limited knowledge of how rain and snow contribute to the recharge of Alpine springs. This study presents a four-year investigation of stable isotopes in precipitation and spring water at the scale of a 240 km2 wide dolomitic massif (Dolomites, Italian Alps) with the aim of determining the proportions of snowmelt and rain in spring water and to provide insights on the variability of these contributions in space and time. Four precipitation sampling devices were installed along a strong elevation gradient (from 725 to 2660 m a.s.l.) and nine major springs were monitored seasonally. The monitoring period comprised three extreme weather conditions, i.e., an exceptional snowpack melting period following the highest snowfall in 30 years, an intense precipitation event (386.4 mm of rain in 48 h), and one of the driest periods ever observed in the region. Isotope-based mixing analysis revealed that rain and snowmelt contributions to spring water were noticeably variable, with two main recharge time windows: a late spring–summer snowmelt recharge period with an average snowmelt fraction in spring water up to 94 ± 9%, and a late autumn–early winter period with a rain fraction in spring water up to 68 ± 17%. Overall, during the monitoring period, snowmelt produced high-flow conditions and sustained baseflow more than rain. We argue that the seasonal variability of the snowmelt and rain fractions during the monitoring period reflects the relatively rapid and climate-dependent storage processes occurring in the aquifer. Our results also showed that snowmelt fractions in spring water vary in space around the mountain group as a function of the elevation of their recharge areas. High-altitude recharge areas, above 2500 m a.s.l., are characterized by a predominance of the snowmelt fraction (72% ± 29%) over the rain contribution. Recharge altitudes of approximately 2400 m a.s.l. also show a snow predominance (65 ± 31%), while springs recharged below 2000 m a.s.l. are recharged mostly from rain (snowmelt fraction of 46 ± 26%). Results from this study may be used to develop more accurate water management strategies in mountain catchments and to cope with future climate-change predictions that indicate a decline in the snow volume and duration in Alpine regions. Full article
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Article
Insights onto Hydrologic and Hydro-Chemical Processes of Riparian Groundwater Using Environmental Tracers in the Highly Disturbed Shaying River Basin, China
Water 2020, 12(7), 1939; https://doi.org/10.3390/w12071939 - 08 Jul 2020
Viewed by 530
Abstract
Understanding the hydrologic and hydrochemistry processes in the riparian area is of great importance for managing and protecting riparian water resources. This paper took a highly disturbed and polluted Shaying River Basin (SRB) of China as the study area. In this research, environmental [...] Read more.
Understanding the hydrologic and hydrochemistry processes in the riparian area is of great importance for managing and protecting riparian water resources. This paper took a highly disturbed and polluted Shaying River Basin (SRB) of China as the study area. In this research, environmental tracers (hydrochemical and isotopic data of222Rn, δ18O, and δD) and corresponding models (two-component mixing model and 222Rn mass balance model) were employed to investigate the hydrologic and associated hydro-chemical process of riparian groundwater. The results indicated that rivers received groundwater discharge located at Xihua (J8), Zhoukou (Y1), Luohe (S2), and Shenqiu (SY2), and the mixing extent with groundwater was greater in wet seasons than in dry seasons. The 222Rn mass balance model showed that the flux of river water leakage was 3.27 × 10−4 m3/(s·m) at the front of Zhoukou sluice while groundwater discharge was 3.50 × 10−3 m3/(s·m) at the front of Shenqiu sluice during the sampling period. The cation exchange and the dissolution/precipitation of aquifer minerals (including calcite, dolomite, gypsum, and halite) were dominated by geochemical processes. The untreated sewage discharge and fertilizer usage were the main anthropogenic activities affecting the hydrochemistry process in surface water and riparian groundwater. Additionally, our results found that nitrate pollutants derived by riparian groundwater were potential threats to river quality at the lower reaches of Jialu River and Shenqiu county of Shaying River, where the nitrate inputs could be larger during the wet seasons because of higher groundwater discharge. Full article
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Article
Seasonally Variant Stable Isotope Baseline Characterisation of Malawi’s Shire River Basin to Support Integrated Water Resources Management
Water 2020, 12(5), 1410; https://doi.org/10.3390/w12051410 - 15 May 2020
Cited by 1 | Viewed by 1490
Abstract
Integrated Water Resources Management (IWRM) is vital to the future of Malawi and motivates this study’s provision of the first stable isotope baseline characterization of the Shire River Basin (SRB). The SRB drains much of Southern Malawi and receives the sole outflow of [...] Read more.
Integrated Water Resources Management (IWRM) is vital to the future of Malawi and motivates this study’s provision of the first stable isotope baseline characterization of the Shire River Basin (SRB). The SRB drains much of Southern Malawi and receives the sole outflow of Lake Malawi whose catchment extends over much of Central and Northern Malawi (and Tanzania and Mozambique). Stable isotope (283) and hydrochemical (150) samples were collected in 2017–2018 and analysed at Malawi’s recently commissioned National Isotopes Laboratory. Distinct surface water dry-season isotope enrichment and wet-season depletion are shown with minor retention of enriched signatures ascribed to Lake Malawi influences. Isotopic signatures corroborate that wet-season river flows mostly arise from local precipitation, with dry-season flows supported by increased groundwater contributions. Groundwater signatures follow a local meteoric water line of limited spread suggesting recharge by local precipitation predominantly during the peak months of the wet-season. Relatively few dry-season groundwater samples displayed evaporative enrichment, although isotopic seasonality was more pronounced in the lowlands compared to uplands ascribed to amplified climatic effects. These signatures serve as isotopic diagnostic tools that valuably informed a basin conceptual model build and, going forward, may inform key identified Malawian IWRM concerns. The isotopic baseline establishes a benchmark against which future influences from land use, climate change and water mixing often inherent to IWRM schemes may be forensically assessed. It thereby enables both source-water protection and achievement of Sustainable Development Goal 6. Full article
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Case Report
An Attempt to Characterize the Recharge of Alluvial Fans Facing the Northern Italian Apennines: Indications from Water Stable Isotopes
Water 2020, 12(6), 1561; https://doi.org/10.3390/w12061561 - 30 May 2020
Viewed by 777
Abstract
Nowadays, climate changes and increased water demand for human and agricultural purposes pose important questions for the groundwater management of alluvial aquifers facing the northern Italian Apennines. The large groundwater withdrawals, coupled with an overall worsening of the water quality, requires a detailed [...] Read more.
Nowadays, climate changes and increased water demand for human and agricultural purposes pose important questions for the groundwater management of alluvial aquifers facing the northern Italian Apennines. The large groundwater withdrawals, coupled with an overall worsening of the water quality, requires a detailed knowledge of the recharge mechanisms of these aquifers that can be useful for further adaptation measures. Concerning the recharge area of the alluvial aquifers (i.e., apices made up of gravelly materials), the present study investigates a dataset made up of 282 water samples for which stable isotopes oxygen-18 (18O) and deuterium (2H) are available. The latter involves precipitations (three rain gauges), surface water (five rivers) and groundwater (twenty wells) from five selected alluvial fans. The study confirms that the different isotopic signatures characterizing rain and river water from this area can be exploited for preliminary characterization of their significance on groundwater recharge. These results lay the foundations for the further use of a suite of environmental tracers (in which a primary role is that of water stable isotopes) at the event-scale (i.e., that of rainfall and/or flood) for eventually estimating the effective quota of recharge linked to precipitation and surface water. Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

1. Title: Water Isotopes Highlight A Reduction of River Water – Groundwater Interactions in the Alluvial Fans from the Northern Italian Apennines

Author: Cervi. F. *, Dadomo A. and Martinelli G.

*Correspondence: Independent researcher, Reggio Emilia, Italy; [email protected]

2. Title: Regional vs Local Isotopic Gradients in Groundwater Recharge Studies: Different Approaches in Peculiar Geological Conditions

Author: Alberto Tazioli *, Stefano Palpacelli and Torquato Nanni

*Correspondence: Dipartimento di Scienze e Ingegneria della Materia, dell’Ambiente ed Urbanistica, Università Politecnica delle Marche, Ancona, Italy; [email protected]

3. Title: Natural Tracers Explain Spatial and Temporal Variations of Spring Recharge in A Dolomitic Mountain Group

Author: Lucianetti G., Penna D. *, Mastrorillo L. and Mazza R.

*Correspondence: University of Florence, Firenze, Italy; [email protected]

4. Title: Dual-Tracer Characterization of Water Flow and Pollutant Transport in A River

Author: Damian Zieba, Przemyslaw Wachniew *

*Correspondence: AGH University of Science and Technology, Krakow MP, Poland; [email protected]

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