The coastal region of Rhodope (NE Greece) is characterized by increased salinization risk leading to groundwater quality degradation and water scarcity. In the context of the MEDSAL Project ( www.medsal.net ), a comprehensive assessment has been carried out concerning the hydrogeochemical characteristics of the area while evaluating the potential impact of geothermal fluids circulation and their ability to move upward and contaminate more surficial water bodies. According to previously conducted surveys, three geothermal wells have been identified in the study area, two of which are representative of the geothermal reservoir, which is hosted within Tertiary molassic sediments. To get an insight into the current hydrogeochemical conditions, a sampling campaign was performed, during which 46 groundwater samples were collected and analyzed for a wide set of parameters. Based on the analytical results, elevated concentrations of certain trace elements presumably associated with geothermal activity (indicatively referred to as B, Li, Sr, and U) have been detected in groundwater wells close to the geothermal one, indicating a possible connection. The relatively elevated groundwater temperature, which reaches up to 25.1 °C, as well as the electrical conductivity values, additionally supports the aforementioned connection. In order to better understand the potential connection of the geothermal influence, the analytical results have been further processed using different tools. The outcomes of the spatial distribution of Li, U, and Ce denoted that the groundwater wells, which are located close to the reported tapped geothermal reservoir and the dominant tectonic structures that prevail in the area, seem to follow a similar hydrogeochemical pattern.

In the current study, the genotypic characteristics such as antimicrobial resistance and virulence genes, and plasmid replicons and phenotypic characteristics such as biofilm formation and antimicrobial resistance of 87 extended-spectrum beta-lactamase (ESBL)-producing E. coli (ESBL-Ec) isolated from 7 water bodies in northern Greece were investigated. Our data show a high prevalence (60.0 %) of ESBL-Ec in surface waters that exhibit high genetic diversity, suggesting multiple sources of their transmission into the aquatic environment. When evaluating the antimicrobial resistance of isolates, wide variation in their resistance profiles has been detected, with all isolates being multi-drug resistant (MDR). Regarding biofilm formation capacity and phylogenetic groups, the majority (54.0 %, 47/87) of ESBL-Ec were classified as no biofilm producers mainly assigned to phylogroup A (35.6 %; 31/87), followed by B2 (26.5 %; 23/87). PCR screening showed that a high proportion of the isolates tested positive for the blaCTX-M-1 group genes (69 %, 60/87), followed by blaTEM (55.2 %, 48/87), blaOXA (25.3 %, 22/87) and blaCTX-M-9 (17.2 %, 15/87). A subset of 28 ESBL-Ec strains was further investigated by applying whole genome sequencing (WGS), and among them, certain clinically significant sequence types were identified, such as ST131 and ST10. The corresponding in silico analysis predicted all these isolates as human pathogens, while a significant proportion of WGS-ESBL-Ec were assigned to extraintestinal pathogenic E. coli (ExPEC; 32.1 %), and urinary pathogenic E. coli (UPEC; 28.6 %) pathotypes. Comparative phylogenetic analysis, showed that the genomes of the ST131-O25:H4-H30 isolates are genetically linked to the human clinical strains. Here, we report for the first time the detection of a plasmid-mediated mobile colistin resistance gene in ESBL-Ec in Greece isolated from an environmental source. Overall, this study underlines the role of surface waters as a reservoir for antibiotic resistance genes and for presumptive pathogenic ESBL-Ec.

Aristino-Traianoupolis area hosts one of the most significant water-dominated low-temperature geothermal fields in Greece. It is located on the southwestern uplifted margin of the Tertiary Evros Delta molassic basin, 10 km east of the town of Alexandroupolis (Thrace, NE Greece). The upper hydrothermal system of the Aristino Geothermal Field (AGF), one of the most promising in continental Greece, contains fluids with temperatures ranging from 51 to 99 °C, within a series of overlapping aquifers at very low depths (100–430 m). The main geothermal anomaly for temperatures higher than 90 °C covers an area of 6 km 2 , to a maximum prospected depth of 500 m below ground surface. The scattered regional anomaly exceeds 50 km 2 and is characterized by excessively high and abruptly changing thermal gradient (42 to 450 °C/km) and heat flow (80–800 mW/m 2 ), that are both typical of a fault-controlled hydrothermal system. Since 1993, the AGF has undergone non-systematic geothermal investigation, with emphasis on low-depth (100–500 m) drilling. This paper provides, for the first time, a synthetic and detailed evaluation of all available temperature data gathered in the last 25 years. The steady-state temperature logs reveal the dominant role of conduction for the upper geothermal system, accompanied, in most cases, by rapidly changing and abnormally high thermal gradients (100–450 °C/km), triggered, most probably, by a deeper system of higher temperature. This hypothesis is also supported by the applied chemical geothermometers, which suggest initial fluid temperatures at 140–150 °C, the hydrochemical characteristics of the fluids hosted in the deeper and most promising investigated reservoir (ignimbrite) of the upper system, and the extrapolated temperatures from the conductive temperature–depth profiles. The lower widespread medium enthalpy hydrothermal system should extend at depths 500–1000 m within volcanics and the expected Eocene limestones and basal clastic series of the Tertiary sequence that have filled the basin. Nevertheless, these assumptions need to be verified by appropriate investigations and new drillings at depths greater than 600–700 m, which would confirm the presence of a productive medium enthalpy reservoir.

The coastal aquifer of the Rhodope region (NE Greece) is a complex groundwater system impacted by various processes that increase groundwater salinization (seawater intrusion, trapped saline lenses, geothermal fluid impact, irrigation return). In the context of the MEDSAL Project (www.medsal.net), a thorough study of its hydrogeochemical characteristics was performed to assess the spatiotemporal variations of groundwater salinization and identify the dynamics of the phenomenon. To this aim, we used a combination of tools, including multivariate statistics analysis (MVSA) and hydrogeochemical modelling, to decipher the mechanism(s) of groundwater salinization and their evolution in time and space. Results from Hierarchical Cluster Analysis (HCA) classified water samples into four (4) diverse groups and seven (7) subgroups that denote different hydrogeochemical and salinization phases. The different processes that control hydrogeochemistry were further assessed using R-mode factor analysis. The outcomes outlined three (3) factors that supplemented the HCA. The dominant factor is related to the cascading processes of salinization, and the secondary factors are related to anthropogenic contamination (N surplus due to agricultural activities) and the impact from the substrate (water-rock interaction). Hydrogeochemical modelling further supported assessments and provided an overview of the spatiotemporal variability of factors and processes affecting groundwater chemistry. A set of saturation indices of key minerals related to the dominant processes identified by the MVSA were calculated and interpolated to capture the spatiotemporal dynamics. Results facilitated the development of a more representative conceptual model about salinization and the key hydrogeochemical processes affecting water quality in the area.

Hydrochemical and isotopic characteristics of fluids from major geothermal fields of middle/low temperature in N/NE Greece are examined [basins: Strymon River (SR), Nestos River Delta (ND), Xanthi–Komotini (XK), Loutros–Feres–Soufli (LFS) and Rhodope Massif]. The geodynamic context is reflected to isotopic/chemical composition of fluids, heat flow values and elevated CO 2 concentrations in emitted fluids. B and Li are derived from leaching of the geothermal systems hosting rocks. δ 18 O H2O , δ 18 O SO4 , δ 13 C CO2 values and chemical compositions of Cl, B and Li of geothermal discharges suggest two distinct source fluids. Fluids in SR exhibit high B/Cl and Li/Cl ratios, suggesting these constituents are derived from associated magmas of intermediate composition (andesitic rocks). Geothermal discharges in LFS exhibit low B/Cl and Li/Cl ratios, implying acid (rhyolitic) magmatism. δ 13 C CO2 and CO 2 /(CO 2 + 10 5 He) ratios in the west part, suggest fluids affected by addition of volatiles released from subducted marine sediments. For the eastern systems, these ratios suggest gas encountered in systems issued from mixing of crustal and mantle-derived volatiles. Isotopic geothermometers reflect, for the same direction, equilibrium processes more ( LFS , XK ) or less (SR) pronounced and discriminate the geothermal field from low to middle [SR, ND (Erasmio)] and middle to high enthalpy [ND (Eratino), LFS, XK].

The potential to map geothermal anomalies using remote sensing information has attracted recently much research, reflecting thus the increasing interest for renewable energy resources. Aim of the present work is to highlight areas with geothermal anomalies, as demonstrated by increased Land Surface Temperature (LST) values, that could potentially indicate possible locations for geothermal field development. We hypothesized that an area with increased geothermal potential can possibly have a surface expression through increased LST, that discriminates it from other areas of low geothermal interest. LST is known to be affected by increased heat flow but also from other parameters such as altitude, land cover and meteorological conditions. Therefore, there is need to develop a methodology capable to extract LST signals corresponding to the geothermal component. To delineate areas with constantly higher LST values from surrounding locations, we analyzed Landsat 8 derived LST time series, and accounted for different land cover types and altitudes. To test our hypothesis, we used a well-known geothermal field in Aristino-Alexandroupolis, NE Greece, where it was shown that spatial means of winter LST were significantly greater within geothermal zones. Furthermore, our results indicated that areas within geothermal fields demonstrate winter LST values greater than a certain threshold value for each different land cover type. Therefore, we developed a logical operator algorithm and applied our methodology to Thrace basin – NE Greece. The produced geothermal potential map depicted correctly spot areas, which make part of the known geothermal fields in Eastern Macedonia and Thrace Tertiary sedimentary basins, but also indicated other possible sites with increased potential for future research.

The sustainable management of lakes and reservoirs requires the determination of their minimum environmental water level. Even though the assessment of minimum water level depends on a number of biotic and abiotic factors of the lake ecosystem, in many cases these factors are not entirely known and, furthermore, their evaluation is usually a challenging and laborious task. On the other hand, the lakes/reservoirs may comprise an important water resource to meet the requirements arising from economic activities. In this paper, the morphological and hydrological features of four lakes of northern Greece were analysed in order to assess their minimum environmental water level. The hydromorphological analysis was based on the relationship of the lake surface area and volume with water level as well as the water inflow from the lake's hydrological catchment area, considering as the lake's critical volume storage, the annual water volume flowing into a lake from its hydrological catchment area with a probability of exceedance 50% of a long time series of hydrological years. By combining morphological and hydrological features, the proposed methodology aimed to extend the analysis based solely on morphological features, and assess more comprehensively the minimum environmental water level in the four lakes, ensuring also the rising from the minimum level to the maximum (overflow) level for most of the hydrological years.

In an attempt to map the soil factors controlling pesticide losses, surface soil samples were collected from 196 sites in the cultivated area of Trifyllia, SW Peloponnese, Greece. Up to now, the pesticide losses risk in the studied area is unknown. For this aim, the following key characteristics that affect movement or binding have been taken into consideration: soil texture, slope and soil organic matter content. A GIS map was compiled from discrete soil variables that affect pesticide losses (leaching and/or runoff). According to soil texture, 3 moderate leaching risk classes, 2 high and 1 low were defined, and the respective classes based on Soil Organic Matter (SOM) content were 3 low risk classes, 2 moderate and 1 class of high risk. The study area consists of two soil slope classes 0-2% and 2-6% which were used to calculate the leaching potential of pesticides. The compiled maps can be used by local authorities in order to minimize the potential negative environmental impacts of pesticide usage at farm level, and to suggest various mitigation strategies. Appropriate farming practices must be applied to decrease leaching or losses by runoff in order to mitigate the pollution of shallow aquifers and surface waters in SW Peloponnese. Rational irrigation management is of high importance as it increases the pesticide effectiveness and reduces off site movement. Moreover, runoff of pesticides can be reduced by using minimum tillage techniques to mitigate soil erosion. Finally, farming systems and practices that increase soil organic matter content (e.g. no tillage) can reduce substantially the risk of water pollution by pesticides.

The application of soil heating can securely transfer the harvest procedure of cultivated plantations to the early or very early season, maximizing in this way the marketable yield and added value. Extended experimentations with geothermal soil heating were elaborated under real operating field conditions based on the running harvest practices and asparagus rows protection techniques. Production and energy data have been collected and processed systematically during the harvest seasons 2002-2007 for dirett use of geothermal waters in Neo Erasmio-Xanthi and for the seasons 2006-2016 for low grade shallow energy (heat pumps) applications in Chrysoupoli-Kavala, both in Northern Greece. The application of maximum heating loads in the order of 100-110 kW/ha along with maximum entering water temperatures at 35 degrees C has been demonstrated as the most cost effective energy option for off season harvest onset. The main objectives of the present comparative approach are (i) the conclusion on a suitable geothermal soil heating scheme for asparagus cultivation and (ii) the quantification and financial evaluation of soil heating impact on asparagus precocity and total yield at commercial scale. The performed analysis gives prominence to low enthalpy and shallow low grade geothermal energy as efficient, valuable and cost effective energy tools in soil heating. (C) 2017 Elsevier Ltd. All rights reserved.

The intense tectonic and volcanic activity in the Hellenic area has caused the accumulation of thermal energy in relatively shallow and, thus, economically accessible depths. This is manifested as numerous low, medium and high enthalpy hydrothermal systems across the country. The geothermal exploration has, thus far, identified more than forty (40) areas of geothermal interest, thirty-two (32) of which are officially characterized as “geothermal fields”. However, only a small fraction of the proven geothermal resources is exploited. Reaching an estimate of around 260 ΜWth, the installed geothermal capacity pertains to heating/cooling and recreation/healing uses. The local geothermal market is dominated by the Ground Source Heat Pumps (63% of the total installed capacity), whereas direct uses are limited to balneotherapy and greenhouse heating, followed by small-scale applications, such as soil heating, dehydration and aquaculture. All new and important exploitation projects are realized in low temperature fields of Northern Greece, where the social acceptance and the support from local authorities have created a favorable investment environment. On the other hand, the share of geothermal energy in the electricity production sector remains zero. In July 2018, an international tender announced by “PPC-Renewables” was concluded successfully, with the selection of a strategic partner for the construction of small power plants (5-8 MWe) in four geothermal areas (Lesvos, Methana, Nisyros and Milos-Kimolos complex). Regarding exploration, the on-going projects concern further research in known low enthalpy areas (Strymon Basin, Akropotamos, Evros Delta, etc.), as well as reconnaissance studies in other promising areas, such as Eastern Thessaly, Lesvos and Lemnos islands.