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The main objective of the present study is to assess Cr(VI) concentrations in groundwater and surface water of Loutraki and Schinos areas. Totally, 38 samples were collected from both areas from April to May 2015. Both surface water and groundwater are of bicarbonate-magnesium type (Mg-HCO3 -) and present very high concentrations of Mg2+ (up to 266...
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Context 1
... study areas (Loutraki and Schinos) are located in the Perachora peninsula at the eastern part of Corinthian Gulf (Fig.1). Loutraki lies at the southern part of Perachora peninsula and it is surrounded by the Gulf of Lechaio. ...
Context 2
... total of 38 water samples were collected from April to May 2015 ( Fig. 1). Groundwater samples were collected from 15 boreholes from Loutraki area (LB) used to cover mainly the drinking water demands of Loutraki's residents. In addition, 5 groundwater samples (GS) were collected from natural springs of Geraneia Mountains, 11 surface water samples from the streams of Geraneia Mountains (SW), 1 surface water ...
Citations
... The present study focuses on the formation of geogenic Cr(VI) and the factors affecting its release into the environment. It has been motivated by the widespread occurrence of ultramafic rocks from the northern to the southern boundaries of Greece, the exploitation of Fe-Ni laterite deposits generating large amounts of metal-rich wastes, and the progressively increasing number of publications linking the elevated Cr(VI) concentrations in groundwater to oxidative reactions of Cr(III) of the Cr-rich bedrock (Dermatas et al., 2015;Economou-Eliopoulos et al., 2017;Kaprara et al., 2015;Megremi et al., 2019;Moraetis et al., 2012;Papazotos et al., 2019;Pyrgaki et al., 2016Pyrgaki et al., , 2020Pyrgaki et al., , 2021Vasileiou et al., 2019). The study examines the levels and potential mobility of Cr species in a natural, complex environment, consisting of serpentinized peridotites and a Fe-Ni sedimentary deposit in an active mining site. ...
Water contamination by geogenic hexavalent chromium is an emerging issue in areas developed on ultramafic rocks and their weathering products. In this study, samples of serpentinites, soil, and laterites were collected and analyzed for the levels of Cr species, distribution into phases of different mobility, mineralogy, Cr oxidation capacity, and leaching of Cr(VI). Total chromium (2176–21,929 mg kg⁻¹) was mainly found in Cr spinels (~ 50% wt as Cr2O3) and Fe (hydr)oxides (2.5% wt). Total Cr(VI) contents (0.49–11.5 mg kg⁻¹) increased from the serpentinites to the soil and lateritic deposit, i.e., during the advanced stages of weathering, which were accompanied by increased Cr mobility. Batch experiments of 500-h duration showed that Cr(VI) released in water at rates of 0.25–1.20 nM h–1. Rates were higher in water of pH 5.7 rather than pH 8.5, because more Cr(VI) was formed during the experimental period. Asbolane-type Mn oxides and Mn-bearing crystalline Fe oxides were responsible for Cr(III) oxidation. Most of the generated Cr(VI) (52–79% of total Cr(VI)) remained solid-bound by adsorption and/or precipitation processes. Because all samples had a self-capacity to oxidize Cr(III), it seems that retention processes will ultimately define the extent of geogenic Cr(VI) contamination of aquatic systems.
... Chromium polluted groundwater has been found in many countries (Kaprara et al., 2015;Margiotta et al., 2012;Villalobos-Aragón et al., 2012;Izbicki et al., 2012). Chromium may originate from natural sources including weathering minerals in ultramafica and ophiolitic rocks and serpentinites, and oxidation and dissolution of related soils and sediments (Oze et al., 2007;Pyrgaki et al., 2017). However, anthropogenic activities are often the major sources of Cr, through its use in a variety of industrial and manufacturing processes. ...
Wide-spread use of chromium in many industrial and manufacturing processes contributes to its presence as a global water pollution issue. In this work, batch experiments were conducted to test the remediation performance of granular activated carbon modified with amorphous FeS (FeS-GAC) for hexavalent chromium (Cr(VI)) polluted water. 76% of Cr(VI) was removed in the first 15 min under neutral condition, compared to a 95% under acidic conditions. Lower initial concentration and reaction temperature favored the removal of Cr(VI). Some electron microscopy and spectral analyses were employed to investigate the reaction mechanism. A multi-step process was hypothesized for the Cr(VI) removal mechanism, including the (i) heterogeneous reaction: adsorption of Cr(VI) onto the solid surface, reaction with FeS, precipitation of Cr(III)/Fe(III) hydroxides, complexation of Cr(VI) with Fe2O3, and the (ii) homogeneously reaction of Cr(VI) and Fe(II)/S(-II). The results of this study demonstrate that the sulfidated GAC exhibites an effective and promising ability for treatment of Cr(VI) polluted water.
... Its consecutive accidental release to the environment results in incidents of serious soil and groundwater contamination. Recent studies, have demonstrated that in areas of ultramafic lithologies occurrence Cr(VI) can be of geogenic origin (Pyrgaki et al. 2016;Chrysochoou et al. 2016;Wood et al. 2010). Furthermore, other studies suggest water-rock interactions in ophiolites constitute a geogenic source for Cr(VI) in groundwater (Apollaro et al. 2011;Margiotta et al. 2012). ...
The origin and distribution of hexavalent chromium, Cr (VI) over four seasonal cycles was investigated through a conceptual model that included three aquifer systems in Cyprus. An extensive water sampling grid covered two sea water intruded coastal aquifers, namely the Kokkinochoria (A1) and Kiti-Pervolia (A2) aquifers and the Troodos massif (A3). Analytical results give a first insight to the presence of Cr (VI) in Cyprus ground and surface waters. The highest Cr (VI) value of 26 μg L−1 is observed in the Troodos area (A3) where Cr(VI) is detected in all sampled water systems (surface and ground/spring). Nonetheless, the highest median values of 4.6 and 4.5 μg L−1 are observed in the Kokkinochoria (A1) and Kiti-Pervolia (A2) study areas respectively, where the local aquifers are under increased pressure from agriculture, urbanization and seawater intrusion. Stable isotopes were used to discern the effect of return irrigation and seawater intrusion. Stable isotope analyses from Troodos samples show two distinct groups of meteoric and near meteoric waters whereas isotopically enriched water is shown to correspond to the Kiti and Kokkinochoria area.
... The weathering processes of ultramafic rocks, depending mainly on the climate conditions and morphology, may result in the formation of laterites, both releasing significant amounts of Cr among other heavy metals (Ni, Co, Mn, Fe). Groundwater from sites characterized by the extensive presence of ultramafic rocks contain more than 10 µg/L Cr(VI), reaching values up to hundreds of µg/L of Cr(VI) [6,[9][10][11][12][13][14][15][16]. The contamination of sites characterized by the extensive presence of ultramafic rocks contain more than 10 μg/L Cr(VI), reaching values up to hundreds of μg/L of Cr(VI) [6,[9][10][11][12][13][14][15][16]. ...
... Groundwater from sites characterized by the extensive presence of ultramafic rocks contain more than 10 µg/L Cr(VI), reaching values up to hundreds of µg/L of Cr(VI) [6,[9][10][11][12][13][14][15][16]. The contamination of sites characterized by the extensive presence of ultramafic rocks contain more than 10 μg/L Cr(VI), reaching values up to hundreds of μg/L of Cr(VI) [6,[9][10][11][12][13][14][15][16]. The contamination of groundwater by Cr may be derived from industrial activities, such as in the Czech Republic (a highly industrialized country in Central Europe) [17], at the area of Friuli Venezia Giulia (northern Italy) [18], the Assopos Basin (Oinofyta or Inofyta, near the Assopos river) in Greece, exhibiting as high as 8000 μg/L Cr(VI) in shallow groundwater [19]. ...
... A common feature of the groundwater from the Neogene lacustrine formations of the Attica Basin, which has been affected by occasionally enclosed (tectonically) serpentinized peridotites, and the C. Evia, Assopos-Thiva Basins and the Loutraki area (Figure 3b,c) is the effect of the seawater intrusion [11][12][13][14][31][32][33][34][35][36][37][38]41], although they have been classified in various water types: the water samples from Attica as a Ca-HCO 3 water type [37], while those from C. Evia and Assopos-Thiva Basins and the Loutraki area are of Mg-HCO 3 type, due to the CO 2 -driven dissolution of dominant minerals, such as serpentine and Mg-carbonates/hydroxides [11,14,31]. In order to better understanding the hydrochemistry of the above aquifers and the driving force of the Cr(VI) stability in contaminated coastal water, representative groundwater samples from the Attica, Assopos-Thiva, and C. Evia Neogene Basins were analyzed in the present study for major and trace elements, including rare earth elements (REEs) and platinum group elements (PGEs) ( Table 1), which were combined with the relative literature data. ...
Chromium concentrations in seawater are less than 0.5 μg/L, but the Cr(VI) in contaminated coastal groundwater affected by Cr-bearing rocks/ores and/or human activities, coupled with the intrusion of seawater may reach values of hundreds of μg/L. A potential explanation for the stability of the harmful Cr(VI) in contaminated coastal aquifers is still unexplored. The present study is an overview of new and literature data on the composition of coastal groundwater and seawater, aiming to provide potential relationships between Cr(VI) with major components in seawater and explain the elevated Cr(VI) concentrations. It is known that the oxidation of Cr(III) to Cr(VI) and the subsequent back-reduction of Cr(VI) processes, during the transport of the mobilized Cr(VI) in various aquifers, facilitate the natural attenuation process of Cr(VI). Moreover, the presented positive trend between B and Cr(VI) and negative trend between δ53Cr values and B concentration may suggest that seawater components significantly inhibit the Cr(VI) reduction into Cr(III), and provide insights on the role of the borate, [B(OH)4]− ions, a potential buffer, on the stability of Cr(VI) in coastal groundwater. Therefore, efforts are needed toward the prevention and/or minimization of the contamination by Cr(VI) of in coastal aquifers, which are influenced by the intrusion of seawater and are threatened by changes in sea level, due to climate change. The knowledge of the contamination sources, hotspots and monitoring of water salinization processes (geochemical mapping) for every coastal country may contribute to the optimization of agricultural management strategies.
... High Cr(VI) concentrations due to both the geology of the area and anthropogenic activities have been observed worldwide [11][12][13][14][15][16][17][18]. The extensive contamination of groundwaters with Cr(VI) (worldwide) necessitates the full understanding of the mechanisms of Cr(III) oxidation by Mn oxides in nature, both to determine the risk of Cr(VI) formation and to the development of techniques to reduce its formation. ...
Chromium occurs in nature mainly in its trivalent or hexavalent form. Hexavalent chromium Cr(VI) is particularly toxic to humans, animals, and plants. The extensive pollution of groundwaters with Cr(VI) necessitates the complete understanding of natural chromium oxidation and reduction mechanisms, both for assessing the risk of hexavalent chromium formation and for the development of techniques for the reduction and removal of Cr(VI) from contaminated water bodies. In this work, the possibility of hexavalent chromium reduction by discarded or low-cost materials, which contain reducing compounds, is investigated regarding the creation of a compact, pump-and-treat filter for Cr(VI) removal from groundwater.
... Nitrification may enhance Cr mobility (Mills et al., 2011), whereas denitrification increases As concentrations in groundwater by reducing As-bearing Fe/Mn-oxyhydroxides (Weng et al., 2017). Seawater intrusion, on the other hand, may trigger elevated concentrations of As and Cr in a coastal aquifer (Pyrgaki et al., 2016;Remoundaki et al., 2016;Morelli et al., 2017;Dehbandi et al., 2019), although the exact role of seawater intrusion in the mobilisation of oxyanion-forming trace elements remains unknown. ...
... This study focused on the mobility of Cr and As in the broader area of the Gerania Mountains, NE Peloponnese, Greece. Previous studies revealed a seawater intrusion regime, elevated concentrations of NΟ 3 -(up to ~210 mg/L), and extremely high concentrations of Cr 6+ (up to ~460 μg/L) in the coastal Schinos area (Papadopoulos and Lappas, 2014;Pyrgaki et al., 2016;Kelepertzis et al., 2019). This region has three principle hydrogeochemical drivers that affect the mobility of these oxyanion-forming trace elements: a) inland carbonate, clastic, and ultramafic rocks with different mineral dissolution regimes; b) coastal areas with seawater intrusion; and c) mild anthropogenic inputs of N as sewage effluents and fertiliser applications. ...
This study aimed to investigate the role of seawater intrusion, nitrogen (N)-cycle, and anthropogenic activities on the elevated groundwater concentrations of oxyanion-forming trace elements in an ultramafic environment and to study the factors controlling the hydrogeochemical characteristics of groundwater in a broader, ultramafic-dominated area of the Gerania Mountains in NE Peloponnese, Greece. Sixty-eight groundwater samples from the a) Schinos area, b) Loutraki area, and c) springs in the Gerania Mountains were analysed for an extensive set of physical and chemical parameters. Elevated concentrations of As, up to 15 μg/L, along the coastline in the Schinos area, and abnormally high concentrations of Cr⁶⁺, up to 460 μg/L, in the central part of the Schinos area, were recorded. The strong spatial correlation of Cr⁶⁺, NO³⁻, and P in the central part of the Schinos area, indicated that the release and subsequent oxidation of geogenic Cr in groundwater can be triggered by N and P anthropogenic inputs, such as a) septic tank effluents or N-bearing fertilisers that lead to nitrification and subsequent soil acidification and drive Cr³⁺ oxidation by the NO2⁻/NO3⁻ redox couple and b) P-bearing fertilisers that cause the desorption of anionic Cr⁶⁺ with simultaneous PO4³⁻ adsorption and contribute additional Cr and other trace elements to the soils. Unlike Cr, geogenic As follows a different pattern of groundwater release mechanism, which is driven by seawater intrusion and initial stages of denitrification along a flowpath near the Schinos coastline, as pointed out by the strong positive correlation coefficient between As and Cl⁻ (0.78). The increased salinity controls the mobilisation of As and other oxyanion-forming trace elements, such as B, Se, and V, resulting in their elevated groundwater concentrations through a) their desorption from the surface of Fe/Mn-oxyhydroxides under alkaline pH conditions, b) the reductive dissolution of Fe/Mn-oxyhydroxides under local hypoxic conditions, and c) an increase in the ionic strength of groundwater favouring the dissolution of Fe/Mn-oxyhydroxides.
... Coupled nitrogen and oxygen isotopes of NO3have proven useful in providing detailed information regarding the NO3sources and transformations in groundwater systems. Here, we applied the combined use of the δ 15 Ν and δ 18 Ο in NO3in groundwater systems in Greece, previously identified to contain elevated Cr(VI) concentrations (e.g., Pyrgaki et al., 2016), with the aim to determine the NO3sources and examine the possible linkage of N cycling to Cr(VI) mobilisation. The porous aquifers from Schinos, Central Evia and Thiva regions have served as prime examples where both anthropogenic NO3contamination and ultramafic-derived Cr(VI) affect groundwater chemistry. ...
Groundwater contamination by geogenic Cr(VI) has been documented in many ultramafic aquifers around the world. At the same time, nitrate (NO3-) exists in groundwater at elevated concentrations as a result of excessive application of fertilizers, animal manure and inappropriate sewage management. Some studies have implied that groundwater bodies of agricultural areas are more vulnerable to Cr(VI) contramination. Here, we examine the linkage between the two contaminants following two geochemical approaches: a) application of laboratory incubation experiments to assess the effect of nitrate in groundwater on Cr(VI) generation from ultramafic rocks, b) use of coupled nitrogen and oxygen isotopes of NO3- in groundwater to examine possible associations between NO3- sources and transformations, and Cr(VI) mobilization.
The first linkage arises from the fact that nitrate acts competitively to chromate anions, previously adsorbed onto solid surfaces. Leaching of Cr-bearing rocks with a neutral NO3- solution released environmentally relevant amounts of Cr(VI) from serpentinites and laterites (43 and 892 μg/kg, respectively). Values of δ15N and δ18O in Cr(VI)-impacted groundwater (range 8-121 μg/L) showed that domestic sewage and nitrification of NH4+-based fertilizers are responsbile for the high NO3- concentrations in central Greece aquifers. We found a clear relationship between dissolved NO3- and Cr(VI) when residential waste cesspool is the source of NO3- in groundwater, possibly indicating an enhanced Cr(VI) generation or mobilization when sewage waste interferes with Cr-bearing ultramafic source material. When geochemical conditions favor the process of nitrification, Cr(VI) generation could be the result of its desorption by NO3-. Acidification caused during oxidation of NH4+ to NO3- also favors the mobilization of Cr(III) and its subsequent oxidation by natural oxidants. We suggest that human activities such as agriculture and inappropriate human waste disposal affect the geochemical occurrence of Cr(VI) in groundwater.
... In Greece, high concentrations of Cr 6+ have been recorded in groundwater of the Psachna basin, Asopos River in Boeotia, Schinos basin, Vergina aquifer, Anthemountas basin, and Sarigkiol basin (Vasilatos et al. 2008;Tziritis et al. 2012;Economou-Eliopoulos et al. 2013;Papadopoulos and Lappas 2014;Vasileiou et al. 2014;Dermatas et al. 2015;Kazakis et al. 2015;Kaprara et al. 2015;Remoundaki et al. 2016;Pyrgaki et al. 2016;Kazakis et al. 2017;Papazotos et al. 2019). ...
The aim of this paper is to provide a methodology including statistical tools and spatial techniques, in order to identify the various potential sources of chromium (Crtot) in the Sarigkiol basin, Western Macedonia, Greece, where elevated concentrations of Crtot in groundwater have been recorded since 1996. Integrated hydrochemical approach and statistical analyses including Pearson’s correlation coefficient, multivariate statistical analyses (factor analysis and hierarchical cluster analysis), and spatial techniques (Moran’s I spatial autocorrelation index and bivariate local indicator spatial association cluster map) were applied to evaluate the chemical analyses of 73 water samples, from irrigation wells, natural springs, and surface water. Both natural and anthropogenic sources of Crtot were recorded; the first (ultramafic-dominated environment) is strongly depicted on the natural spring water, in which Crtot concentrations as high as ~ 130 μg/L were recorded, whereas the second (agricultural activities) acts synergistically in the irrigation wells of the Sarigkiol basin, in which strong correlations of Crtot, P, and NO3⁻ were defined. The paper highlights its findings by outlining the potential sources of elevated concentrations of Cr⁶⁺ in the Sarigkiol basin, stressing the need for a closer attention on the role of agricultural activities as an important, though commonly neglected, anthropogenic source of Crtot in groundwater.
... Coupled nitrogen and oxygen isotopes of NO3have proven useful in providing detailed information regarding the NO3sources and transformations in groundwater systems. Here, we applied the combined use of the δ 15 Ν and δ 18 Ο in NO3in groundwater systems in Greece, previously identified to contain elevated Cr(VI) concentrations (e.g., Pyrgaki et al., 2016), with the aim to determine the NO3sources and examine the possible linkage of N cycling to Cr(VI) mobilisation. The porous aquifers from Schinos, Central Evia and Thiva regions have served as prime examples where both anthropogenic NO3contamination and ultramafic-derived Cr(VI) affect groundwater chemistry. ...
High nitrate (NO3-) concentrations in groundwater occur in many areas around the world, largely as a result of excessive application of fertilisers, animal manure and inappropriate sewage management. A series of recent publications have established that naturally-occurring Cr(VI) is prevalent in groundwater associated with ultramafic aquifers in Greece (e.g., Kaprara et al., 2015). There is some evidence that increased NO3-in alluvial aquifers of agricultural areas may exacerbate the mobilisation of Cr(VI) via intensive groundwater recharge through the vadose zone and associated increased contact with Cr-containing minerals or nitrification of ammonium in fertilisers (Mills et al., 2011). Coupled nitrogen and oxygen isotopes of NO3-have proven useful in providing detailed information regarding the NO3-sources and transformations in groundwater systems. Here, we applied the combined use of the δ 15 Ν and δ 18 Ο in NO3-in groundwater systems in Greece, previously identified to contain elevated Cr(VI) concentrations (e.g., Pyrgaki et al., 2016), with the aim to determine the NO3-sources and examine the possible linkage of N cycling to Cr(VI) mobilisation. The porous aquifers from Schinos, Central Evia and Thiva regions have served as prime examples where both anthropogenic NO3-contamination and ultramafic-derived Cr(VI) affect groundwater chemistry. A total of 28 groundwater samples from productive wells and bores were collected from the three study areas during November 2017 (dry period): 9 samples from Schinos (borehole depth ranging from 4 to 55 m), 13 samples from Evia (depth ranging from 4 to 250 m) and 6 samples from Thiva (depth ranging from 150 to 250 m). Concentrations of dissolved NO3-and Cr(VI) were determined after well-established international protocols for water sampling, handling, preservation and analysis. The δ 15 Ν and δ 18 Ο of NO3-were analysed using the bacterial denitrification method. Hexavalent Cr concentrations for this specific data set ranged from 10 to 112 μg/l in Thiva, 12 to 121 μg/l in Schinos and 11 to 189 μg/l in Evia. Nitrate concentrations showed a different distribution, with the highest concentrations determined in Evia (median 120 mg/l, range from 18 to 334 mg/l), followed by those in Thiva (median 66 mg/l, range from 21 to 151 mg/l) and Schinos (median 46 mg/l, range from 9 to 70 mg/l). The isotopic composition of NO3-for the whole data set ranged from 2.4 ‰ to 21 ‰ for δ 15 N, and from-0.73 ‰ to 15.3 ‰ for δ 18 Ο. Potential sources of NO3-in the studied aquifers include the application of synthetic fertilisers and manure in the agricultural fields of Evia and Thiva regions, and the existence of residential waste cesspools in Schinos and Evia areas. The NO3-isotope ratios in most studied water samples fall in the compositional range of NH4 + in fertiliser, soil N and manure/septic waste (Fig. 1). The soil N cannot be considered to be the main origin of NO3-because NO3-concentrations were much higher than expected concentrations produced by the mineralisation of soil organic N. A cluster of samples from Schinos and Evia exhibited δ 15 N values close to or higher than 8‰, falling in the field of animal and/or human waste; especially for Schinos, and given the absence of intensive agricultural practices in this area, it is deduced that domestic sewage is the main source of NO3-in groundwater. On the other hand, isotope data indicated that nitrification of NH4 +-based fertilisers is responsible for the high NO3-concentrations measured in groundwater from Thiva, and partially from Evia. The high [NO3-]/[Cl-] ratios identified in these water samples signified that chemical fertilisers are the principal source of dissolved NO3-. No clear relationship could be established between Cr(VI) and NO3-in this study, when the entire data set was taken into account; several samples with elevated Cr(VI) concentrations exhibited low NO3-concentrations and vice versa. Nonetheless, we found a significantly positive correlation between these solutes in the case of Schinos groundwater system (r=0.83, p=0.005) which might indicate an enhanced Cr(VI) generation when sewage wastes interfere with Cr-containing ultramafic source material. For Evia and Thiva groundwater samples, the nitrification of NH4 + in fertilisers, as evidenced by the isotope data of δ 15 Ν and δ 18 Ο in NO3-, could be responsible for the production of environmentally relevant amounts of Cr(VI) because the increased concentrations of H + may increase the mobility of Cr(III) and its subsequent oxidation on Mn oxides (Mills et al., 2011). Although, it is difficult to support a direct link between the isotope data and Cr(VI) concentrations (Fig. 1), it appears that the process of nitrification, either from human/animal waste or synthetic fertilisers, trigger the geochemical occurrence of geogenic Cr(VI) in groundwater. Both NO3-and Cr(VI) occur primarily in oxic groundwater, deduced by the high Eh and dissolved oxygen (DO) values measured in the samples, providing a deciding geochemical environment that promotes the persistence of these constituents in solution. Locally in the aquifer, decreasing DO concentrations along flowpaths favour the process of denitrification. This is evident in one groundwater sample from Schinos (δ 15 Ν and δ 18 Ο values of 21.5 ‰ and 15.3 ‰, respectively) that exhibited the lowest Cr(VI) concentration (8 μg/l) determined in the data set. The results of this study assist in the clear identification of NO3-contamination origin and provide science-based information to the general public and municipal key stakeholders for a more effective water management planning. Figure 1. Isotopic values of NO3-for the studied groundwaters along with graduated symbol plot of Cr(VI) concentrations.
... However, it must be highlighted that the risk of sea water intrusion in the coastal zone is high during the dry season. This is also proved by the fact that electrical conductivity and chloride concentrations increase near the coastal zone (Pyrgaki et al., 2016). Therefore, water managers must take measures in order to avoid aquifer overpumping during summer months in order to minimise the risk of sea water intrusion in the coastal part of the aquifer system. ...
According to the European groundwater directive (2006/118/EC), groundwater bodies must be protected from qualitative and quantitative degradation. According to the 1st revision of the National Water Management Plan for the River Basin District of Attica, the groundwater body of Loutraki is characterised by a good qualitative and quantitative status. The water demand (mainly for drinking purposes) of Loutraki is covered exclusively by the alluvial aquifer located at the southern part of the basin. It is estimated that the annual groundwater abstractions from the alluvial aquifer are approximately 2.5 million m3. During the summer, the groundwater abstractions are doubled as Loutraki is a popular touristic resort and this causes an additional pressure on the aquifer. Within such a framework, the scope of the present study is to assess the variation of groundwater level between the wet and dry season as well as to compare the present and the past piezometric level for the studied part of the aquifer by using Geographical Information Systems. Several researchers have used GIS techniques for the assessment of groundwater-level fluctuation (Tiwari et al., 2017).
