Nerantzis Kazakis

Occurrence of Cr(VI) in drinking water of Greece and relation to the geological background

This study provides a survey on potential Cr(VI) exposure attributed to drinking water in Greece. For this reason, a wide sampling and chemical analysis of tap waters from around 600 sites, supplied by groundwater resources, was conducted focusing on areas in which the geological substrate is predominated by ultramafic minerals. Results indicate that although violations of the current chromium regulation limit in tap water are very rare, 25% of cases showed Cr(VI) concentrations above 10 μg/L, whereas Cr(VI) was detectable in 70% of the samples (>2 μg/L). Mineralogy and conditions of groundwater reservoirs were correlated to suggest a possible Cr(VI) leaching mechanism. Higher Cr(VI) values are observed in aquifers in alluvial and neogene sediments of serpentine and amphibolite, originating from the erosion of ophiolithic and metamorphic rocks. In contrast, Cr(VI) concentration in samples from ophiolithic and metamorphic rocks was always below 10 μg/L due to both low contact time and surface area, as verified by low conductivity and salt concentration values. These findings indicate that under specific conditions, pollution of water by Cr(VI) is favorable by a slow MnO2-catalyzed oxidation of soluble Cr(III) to Cr(VI) in which manganese products [Mn(III)/Mn(II)] are probably re-oxidized by oxygen.

Geogenic Cr oxidation on the surface of mafic minerals and the hydrogeological conditions influencing hexavalent chromium concentrations in groundwater

This study aims to specify the source minerals of geogenic chromium in soils and sediments and groundwater and to determine the favorable hydrogeological environment for high concentrations of Cr(VI) in groundwaters. For this reason, chromium origin and the relevant minerals were identified, the groundwater velocity was calculated and the concentrations of Cr(VI) in different aquifer types were determined. Geochemical and mineralogical analyses showed that chromium concentrations in soils and sediments range from 115 to 959 mg/kg and that serpentine prevails among the phyllosilicates. The high correlation between chromium and serpentine, amphibole and pyroxene minerals verifies the geogenic origin of chromium in soils and sediments and, therefore, in groundwater. Manganese also originates from serpentine, amphibole and pyroxene, and is strongly correlated with chromium, indicating that the oxidation of Cr(III) to Cr(VI) is performed by manganese-iron oxides located on the surface of Cr-Mn-rich minerals. Backscattered SEM images of the soils revealed the unweathered form of chromite grains and the presence of Fe-Mn-rich oxide on the outer surface of serpentine grains. Chemical analyses revealed that the highest Cr(VI) concentrations were found in shallow porous aquifers with low water velocities and their values vary from 5 to 70 μg/L. Cr(VI) concentrations in ophiolitic complex aquifers ranged between 3 and 17 μg/L, while in surface water, karst and deeper porous aquifers, Cr(VI) concentrations were lower than the detection limit of 1.4 μg/L.

Seawater intrusion mapping using electrical resistivity tomography and hydrochemical data. An application in the coastal area of eastern Thermaikos Gulf, Greece.

The aim of this study was to determine the extent and geometrical characteristics of seawater intrusion in the coastal aquifer of the eastern Thermaikos Gulf, Greece. Hydrochemical data and geoelectrical measurements were combined and supplemented to determine the hydrochemical regime of the study site in regard to seawater phenomena. Chemical analysis of groundwater was performed in 126 boreholes and fifteen electrical resistivity tomographies (ERT) were measured, whereas in two sites the ERT measurements were repeated following the wet season. The Cl(-) concentrations recorded reached 2240 mg/L indicating seawater intrusion which was also verified by ionic ratios. The ionic ratios were overlapped and a seawater intrusion map (SWIM) was produced. A significant part of the coastal aquifer (up to 150 km(2)) is influenced by seawater intrusion. The areas with the most intensive salinization are located between Nea Kallikratia-Epanomi and Aggelochori-Peraia. According to the ERTs, in the influenced areas the salinization of the aquifer exceeds 1 km toward the mainland and its depth reaches 200 m. In the area surrounding Thessaloniki airport, the ERTs revealed salinization of the upper aquifer to depths of up to 40 m, whereas the lower aquifer is uninfluenced. This abnormal distribution of seawater intrusion demonstrates the value of geoelectrical methods in the study of seawater intrusion especially in areas with limited available hydrochemical data.

Assessment of the Intrinsic Vulnerability of Agricultural Land to Water and Nitrogen Losses via Deterministic Approach and Regression Analysis

A set of indices was developed in order to classify the vulnerability of agricultural land to water and nitrogen losses (LOS), setting a basis for the integrated water resources management in agricultural systems. To calibrate the indices using multiple regression analysis, the simulation results of Groundwater Loading Effects of Agricultural Management Systems (GLEAMS) model for combinations of different soil properties, topography, and climatic conditions of a reference field crop were used as “observed values.” GLEAMS quantified (1) the annual losses of the percolated water beneath the root zone, (2) the annual losses of the surface runoff, (3) the annual losses of the nitrogen leaching beneath the root zone, and (4) the annual losses of nitrogen through the surface runoff, which were used to calibrate the following indices LOSW-P, LOSW-R, LOSN-PN, and LOSN-RN, respectively. All the simulations to gain the LOS indices were carried out for the same reference field crop, the same nitrogen fertilization, and the same irrigation practice, in order to obtain the intrinsic vulnerability of agricultural land to water and nitrogen losses. The LOS indices were also combined to derive nitrogen concentrations in the percolated and in the runoff water. Finally, the connection of LOS indices with the groundwater was performed using an additional equation, which determines the minimum transit time of the percolated water to reach the groundwater table.

Estimation of hydraulic parameters in a complex porous aquifer system using geoelectrical methods

Geoelectrical methods have been widely used for the estimation of aquifer hydraulic properties. In this study, geoelectrical methods were applied in a lithologically and hydrochemically complex porous aquifer to estimate its porosity, hydraulic conductivity and transmissivity. For this purpose, the electrical resistivity of the aquifer as well as the electrical conductivity of the groundwater was measured in 37 sites and wells. Initially, the Archies law was used to generate sets of cementation factor (m) and alpha (α) parameter from which the mode values of α=0.98 and m=1.75 are representative of the studied aquifer. The transmissivity of the aquifer varies from 5.1×10(-3) to 3.1×10(-5)m(2)/s, whereas the mean value of its porosity is 0.45. The hydraulic conductivity of the aquifer which was calculated according to Archies law varies from 2.08×10(-6) to 6.84×10(-5)m/s and is strongly correlated with the pumping tests hydraulic conductivity. In contrast, the hydraulic conductivity which was calculated using Dar-Zarrouk parameters presents lower correlation with the pumping tests hydraulic conductivity. Furthermore, a relation between aquifer resistivity and hydraulic conductivity was established for the studied aquifer to enable the estimation of these parameters in sites lacking data.

Origin of hexavalent chromium in groundwater: The example of Sarigkiol Basin, Northern Greece

Hexavalent chromium constitutes a serious deterioration factor for the groundwater quality of several regions around the world. High concentrations of this contaminant have been also reported in the groundwater of the Sarigkiol hydrological basin (near Kozani city, NW Greece). Specific interest was paid to this particular study area due to the co-existence here of two important factors both expected to contribute to Cr(VI) presence and groundwater pollution; namely the areas exposed ophiolitic rocks and its substantial fly ash deposits originating from the local lignite burning power plant. Accordingly, detailed geochemical, mineralogical, hydro-chemical, geophysical and hydrogeological studies were performed on the rocks, soils, sediments and water resources of this basin. Cr(VI) concentrations varied in the different aquifers, with the highest concentration (up to 120μgL-1) recorded in the groundwater of the unconfined porous aquifer situated near the temporary fly ash disposal site. Recharge of the porous aquifer is related mainly to precipitation infiltration and occasional surface run-off. Nevertheless, a hydraulic connection between the porous and neighboring karst aquifers could not be delineated. Therefore, the presence of Cr(VI) in the groundwater of this area is thought to originate from both the ophiolitic rock weathering products in the soils, and the local leaching of Cr(VI) from the diffused fly ash located in the area surrounding the lignite power plant. This conclusion was corroborated by factor analysis, and the strongly positively fractionated Cr isotopes (δ53Cr up to 0.83‰) recorded in groundwater, an ash leachate, and the bulk fly ash. An anthropogenic source of Cr(VI) that possibly influences groundwater quality is especially apparent in the eastern part of the Sarigkiol basin.

Comparison of three applied methods of groundwater vulnerability mapping: A case study from the Florina basin, Northern Greece

Three different methods of intrinsic groundwater vulnerability mapping were applied in the alluvial aquifer of Florina basin (NW Greece), covering an area of 180 km2. Vulnerability maps were produced using the parametric methods DRASTIC, GOD, AVI and the results are compared and evaluated. The three methods use different number of parameters with different weight and produce relatively different results. The comparison between these methods shows that the GOD method has the stronger correlation with the other two methods and produces vulnerability maps comparable with DRASTIC and AVI method.

Magnetic characteristics and trace elements concentration in soils from Anthemountas River basin (North Greece): discrimination of different sources of magnetic enhancement

The magnetic minerals (e.g., iron oxides) that are present in soils can be easily identified by using rock-magnetic techniques. Increased magnetic susceptibility of soils may reflect particles rich in iron oxides of anthropogenic, lithogenic, and pedogenic origin. Therefore, reliable discrimination of these sources is required, especially in areas where neither of them is dominant. The aim of the present study is to assess the lithogenic and anthropogenic contributions to iron-oxide mineralogy of soils in the area of the Anthemountas River basin in the southeast part of Thessaloniki city. Previous investigations within the study area, based on spatial distribution of magnetic susceptibility, revealed the presence of two magnetically enhanced regions. Therefore, the present study is focused on these two areas, in order to characterize the origin of magnetic enhancement. Detailed magnetic analyses include properties reflecting the type, concentration, and relative grain-size distribution of magnetic particles. Moreover, trace element concentration is determined with an aim to establish the link between low-field mass-specific magnetic susceptibility and concentration of Fe, Cr, Ni, Mn, Pb, Zn, and Ti. These findings are supported by descriptions of the micromorphology performed by scanning electron microscopy and determination of elemental composition by energy-dispersive spectrometer analyses in selected points. Finally hierarchical cluster analysis is applied to classify the soil samples into appropriate groups according to their magnetic properties. The results reveal that magnetic measurements provide a useful tool for the discrimination between different magnetic sources responsible for the enhancement of magnetic susceptibility in soils. Low-field mass-specific magnetic susceptibility reflects increased concentration of trace elements, while its combination with other magnetic measurements clearly differentiates the origin of magnetic enhancement in both parts of the study area.

Support of irrigation water use and eco-friendly decision process in agricultural production planning

Abstract In this paper a Multiple Criteria Mathematical Programming model has been developed integrating vulnerability maps; its purpose is to optimize and facilitate the decision making process relating to the problems of water management, land use and environmental protection. The model is used to support irrigation water use and eco-friendly decision processes in agricultural production planning. It has been developed in the context of the research project entitled EU Water (transnational integrated management of water resources in agriculture for European water emergency control). For accessing the vulnerability of agricultural land to water and nitrogen losses, a set of indices were utilised. It was implemented in the Sarigkiol basin in the north-eastern part of the Kozani prefecture in Northern Greece, combining different criteria to a utility function under a set of constraints concerning different categories of labour, land, available capital, etc. On the same time the model is taking into account the vulnerability maps which have been developed for the area. The aim of the study was to achieve optimum crop plans in the aforementioned area and it was further used to simulate different scenarios and policies, due to changes on different social, economic and environmental parameters (e.g. different levels of chemicals or water consumption per crop). The decision maker can get alternative production plans and agricultural land uses as well as the social, economic and environmental impact of different policies. Results show that the model can be considered as an important planning tool enabling the regional authorities to design optimal spatial development policies and protect groundwater from the excessive fertilizer and other pollution agents use.

A fuzzy multicriteria categorization of the GALDIT method to assess seawater intrusion vulnerability of coastal aquifers

Groundwater constitutes the primary source of fresh water for >1.2 billion people living in coastal zones. However, the threat of seawater intrusion is widespread in coastal aquifers mainly due to overexploitation of groundwater. In the present study, a modified fuzzy multicriteria categorization into non-ordered categories method was developed in order to modify the standard GALDIT method and assess seawater intrusion vulnerability in a coastal aquifer of northern Greece. The method is based on six parameters: groundwater occurrence, aquifer hydraulic conductivity, groundwater level, distance from the shore, impact of the existing status of seawater intrusion, and aquifer thickness. Initially, the original method was applied and revealed a zone of high vulnerability running parallel to the coastline and covering an area of 8.6km2. The modified GALDIT-F method achieved higher discretization of vulnerability zones which is essential to build a rational management plan to prevent seawater intrusion. The GALDIT-F approach also distinguished an area of the aquifer that is influenced by geothermal fluids. In total, twenty-five categories were produced corresponding to different vulnerability degrees according to the initial method (High, Moderate, Low) as well as the area influenced by geothermal fluids. Finally, a road map was developed in order to adapt management strategies to GALDIT-F categories and prevent and mitigate seawater intrusion. The proposed management strategies of the coastal aquifer include managed aquifer recharge (MAR) implementation, reallocation of existing wells, optimization of pumping rates during the hydrological year, and a detailed monitoring plan.