Dear Colleagues,

High levels of inorganic compounds in groundwater represent a significant problem in many parts of the world, with important economic, social, and environmental drawbacks. Natural groundwater composition mainly derives from water–rock interactions, both in vadose and saturated zones, but depends also on biological processes, residence time, and the initial composition of recharge water. Contamination from industrial, agricultural, and urban areas often overlaps on the natural features of groundwater, and the assessment of the impact of anthropogenic activities might be challenging.

This is a fundamental issue in groundwater management, in particular when the concentration of inorganic compounds exceeds the threshold values set for the evaluation of the good groundwater chemical status of groundwater, as requested by many environmental regulations. The distinction of high natural background levels (NBLs) of chemical elements in groundwater from human-derived contamination is needed to clearly define the environmental objectives for groundwater bodies as well as the reclamation targets for contaminated sites.

A variety of methodologies have been adopted by different countries to assess the NBLs of chemical elements in groundwater that are potential contaminants and may be hazardous for human health and groundwater-dependent ecosystems. Recent research has demonstrated the need for an enhanced understanding of the interaction of natural and anthropogenic processes affecting groundwater quality finalised to the assessment of the boundary between pristine and polluted.

This Special Issue aims to update the knowledge on methods and approaches used to derive NBLs, from site-specific to catchement-wide or regional scale. We welcome the submission of papers reporting the development of innovative methods to determine the NBL and new criteria for a correct evaluation of anthropogenic impacts on groundwater quality, including conceptual model definition, monitoring strategies, geochemical modelling, and statistical and spatial analysis of geochemical data. The final goal is a Special Issue bringing together new insights on how the NBL is dealt with, from different regions of the world.

Dr. Elisabetta Preziosi
Dr. Marco Rotiroti
Dr. M. Teresa Condesso de Melo
Sr. Sci. Klaus Hinsby
Guest Editors

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• Geochemical modelling
• Water–rock interactions
• Spatial analysis
• Geostatistics
• Multivariate statistical analysis
• Threshold values
• Groundwater pollution.

Tentative title: Ambient background values of selected chemical substances in four grouped groundwater bodies in the Pannonian region of the Republic of Croatia

 Authors: Nakić, Z.*, Kovač, Z.*, Parlov, J.* and Perković D.*

* University of Zagreb, Faculty of mining, geology and petroleum engineering

corr. author: Nakić Z., e-mail: [email protected]

Abstract:

A groundwater quality is a consequence of cumulative effects of natural and anthropogenic processes occurring in the unsaturated and saturated zone, which in certain conditions can lead to elevated concentrations of chemical substances in groundwater. In this paper, the concept of determining the ambient background value of a chemical substance in groundwater is applied because the long-term effects of human activity influence the increase in concentrations of substances in the environment. Background values ​​were determined for selected chemical substances in four grouped groundwater bodies in the Pannonian area of ​​the Republic of Croatia, according to the demands of the EU Groundwater Directive. The selected groundwater bodies are typical, according to the aquifer typology, for the Pannonian area of ​​the Republic of Croatia. Model-based objective methods, Cumulative Distribution Function (CDF) and Lepeltier method, as well as the simple Preselection method, were used in this paper, depending on the proportion of <LOQ values ​​in the dataset for each grouped groundwater body. CDF and Lepeltier method can be used if the proportion of <LOQ values is less than 30% of each dataset. If the proportion of <LOQ values is higher than 30%, it is recommended to use the Preselection method with the adequate confidence level.

Tentative title: GuEstNBL: The software for the Guided Estimation of the Natural Background Levels of the
aquifers

Authors: Francesco Chidichimo, Michele De Biase, Alessandra Costabile, Enzo Cuiuli, Orsola Reillo,
Clemente Migliorino, Salvatore Straface

Abstract:

The knowledge of the Natural Background Levels (NBL’s) of targeted chemical elements, characterizing a specific groundwater body, represents a fundamental information for all those environmental agencies responsible for the protection, management and remediation of the territory. The large number of areas subject to strong anthropogenic pressures, of a different nature and magnitude, makes the job of the aforementioned control authorities particularly hard. The process to distinguish effective anthropogenic contamination from natural conditions and to define realistic environmental clean-up goals goes through the computation of several mutually dependent statistical methods, some of which have not trivial resolution and interpretation. In this study, a new tool designed to drive, those working in the sector, into the articulated path towards the assessment of the NBL's is presented. The application software has been developed in order to read the environmental input data and to return the NBL estimate, of a given chemical element, following a wizard which allows the implementation of two methodologies: The Component Separation or the Pre selection. The project was born from the collaboration between the Department of Environmental Engineering of the University of Calabria and the Department of Environmental Policies of the Calabria Region. The software has been used for the NBL estimation of selected chemical species in the potentially contaminated industrial site located in Lamezia Terme, Italy. The developed calculation program is going to be the official evaluation tool of the Calabria Region for the identification of groundwater thresholds.

Tentative title: Evaluation of the Natural background levels of groundwater in the Water Framework Directive in France – adaptation and evolution of the methodology with working scales and data availability

Authors: Gourcy L., Chery L., Blum A., Malcuit E., Lions, J., Tailame A.L., Ratsimihara T., Arnaud L., Brenot A., Devau N.

Affiliation: BRGM, Orléans, France

Abstract: 

From 2006 to present various studies were carried out to define the natural background level of dissolved elements in groundwater. The first studies were based in the existing chemical data and geological knowledge. A national methodology and map of the risk of high concentration of elements of natural origin were proposed. National expertise and European collaboration through BRIDGE led to the determination of As, B, F, Ni, Sb, Se as the main elements of interest. Additional studies were carried out in the French overseas departments from 2006 to 2008.

From 2010 to 2015 other studies were developed at basin and regional scales deepening the geochemical processes understanding and permitting the calculation of expected concentrations of natural origin. In many cases, surface water was taken into account.

The increase number of data of high quality permitted in 2017 the estimation of the expected concentration of elements by main lithologies in France.  

An advanced method based on non-parametric statistics was proposed to fulfill the need of the new directive (2014/80/UE) and request to have information on groundwater under anthropogenic pressure. The method developed for the Loire-Bretagne basin has been adapted and proposed to other European countries within the GEOERA HOVER project.

Keyword: natural background level, groundwater, statistical data treatment, lithology, France

Title: Assessing natural background levels in the Apulia groundwater bodies (southern Italy)
Authors: R. Masciale, S. Amalfitano, E. Frollini, S. Ghergo, M. Melita, D. Parrone, E. Preziosi, M. Vurro, A. Zoppini, G. Passarella
Affiliation: Water Research Institute, National Research Council (IRSA-CNR)
Abstract: Defining natural background levels (NBLs) of geochemical parameters in groundwater is a key element for establishing appropriate threshold values for water quality assessments. In the Apulia region (Italy), Mesozoic carbonate sequences and Quaternary clastic sediments host the main groundwater reservoirs divided into 29 groundwater bodies (GWBs). Past monitoring activities showed nitrates, chloride, electrical conductivity, sulfate, boron, iron and manganese values exceeding the national standards, very likely due to the interference with saltwater along the coast and intensive agricultural practices. The abundance of iron and manganese is probably due to clay-rich lenses interbedding of the carbonate sequence and filling of karst cavities. In the frame of the VIOLA project, this study applied, and tested the Italian guidelines (ISPRA/CNR 2017) for the NBLs definition to Fe and Mn concentration at the GWB scale utilizing half-yearly 2016-2018 groundwater quality data. A web-based software tool was developed to standardize the whole procedure and provide graphical outputs. Following the Italian guidelines, a pre-selection procedure was applied to remove all those monitoring sites affected by an evident anthropization, highlighted by high values of nitrogen compounds and salinity parameters. The residual sites were used to assess the NBLs. Unfortunately, being the pre-selection method strongly based on salinity parameters, the resulting density of monitoring sites/total observations decreased significantly. This led to low or very low confidence levels of the NBLs’ estimates, mainly in the coastal GWBs, and has paved the way to experimenting with novel insights to trace the origin of salinity in such GWBs.

Title: eNaBLe, an on-line tool to evaluate Natural Background Levels following the Italian Guidelines
Authors: Daniele Parrone, Eleonora Frollini, Elisabetta Preziosi, Stefano Ghergo
Author Affiliations: IRSA-CNR, Water Research Institute - National Research Council, Via Salaria km 29.300, PB 10, 00015 Monterotondo (Rome), Italy
Abstract: Inorganic compounds in groundwater may derive from both natural processes and anthropogenic activities. The assessment of Natural Background Levels (NBLs) is often useful to distinguish these sources. The approaches for the NBLs assessment can be classified as geochemical (e.g. the well-known pre-selection method) or statistical, the latter involving the application of statistical procedures to separate natural and anthropogenic populations. National Guidelines for the NBLs assessment in groundwater have been published in Italy (ISPRA 2017), based mainly on the pre-selection method. The Guidelines propose different assessment paths according to the sample size in spatial/temporal dimension and the type of the distribution of the pre-selected dataset, taking also into account the redox conditions of the groundwater body. The obtained NBLs are labelled with a different confidence level in function of number of total observations/monitoring sites, extension of groundwater body and aquifer type (confined or unconfined). To support the implementation of the Guidelines, the on-line tool eNaBLe, written in PHP and using MySQL as DBMS, has been developed. The main goal of this paper is to describe the functioning of eNaBLe and test the tool on a case study in central Italy. We calculated the NBLs of As, F, Fe and Mn in the southern portion of the Mt. Vulsini GWB, within the volcanic province of Latium (Central Italy), also separating the reducing and oxidizing facies. Specific results aside, this study allowed to verify the functioning and possible improvements of the online tool and to identify some criticalities in the procedure NBLs assessment at the groundwater body scale.
Tentative Submission Date: 01/12/2020
First name: Eleonora
Last name: Frollini
Email address: [email protected]
Affiliation: IRSA-CNR, Water Research Institute - National Research Council, Via Salaria km 29.300, PB 10, 00015 Monterotondo (Rome), Italy