Groundwater and soil geochemistry of the Eastern Kopaida region (Beotia, central Greece)

The Kopaida plain is a cultivated region of Eastern Greece, with specific characteristics related to the paleogeographic evolution and the changes in land use of the area. This study examines the geochemical conditions of the groundwater and soil, and the correlations between them. 70 samples (50 samples of groundwater and 20 samples of soil) were collected in order to asses the geochemical status and the major natural and manmade affecting processes in the region. Extended chemical analyses were carried out including the assessment of 28 parameters for groundwater and 13 for soil samples. The results revealed that groundwater geochemistry is influenced primary by natural processes such as the geological background, and secondary by manmade impact mainly deriving from the extended use of Nitrogen-fertilizers and the over-exploitation of boreholes. Soil geochemistry is influenced exclusively by natural processes, such as weathering of the prevailing geological formations. Chemical analyses and the statistical processing of data revealed that the major factor for the geochemical status of soils is the weathering of the karstic substrate, as well as the existing lateritic horizons and a weak sulfide mineralization

The use of hydrogeochemical analyses and multivariate statistics for the characterization of groundwater resources in a complex aquifer system. A case study in Amyros River basin, Thessaly, central Greece

The present study investigates the hydrogeochemical regime of a complex aquifer system in a highly cultivated area of Thessaly, central Greece. To do so, totally forty (40) groundwater samples were collected for three aquifer units with diverse geological and hydrogeological attributes and analyzed for 77 parameters. Data processing was accomplished with the joint use of classic hydrogeochemical techniques including major ion molar ratios and graphical interpretation, as well as multivariate statistical methods including R-mode factor (FA) and hierarchical cluster analysis (HCA). Results showed that major ion hydrogeochemistry is characterized by the prevalence of calcium (median = 81 mg/L) and bicarbonates (median = 308 mg/L) in the following descending order of concentrations for cations Ca2+>Mg2+>Na+>K+ and anions HCO3 −>NO3 −>SO4 2−>Cl−, respectively. Nitrate values are elevated (median = 23 mg/L), especially in the porous quaternary aquifer, indicating the ongoing agricultural impact from the excessive use of nitrogen fertilizers and manure. The results of multivariate statistics highlighted four factors that chiefly control 81.4 % of overall hydrogeochemistry, related with both geogenic and anthropogenic impacts. The geogenic impact is mainly attributed to the geological substrate and secondarily to the ongoing geochemical (redox) conditions which in turn enrich or deplete groundwater solution with different ions; anthropogenic impact is mainly related with the extensive agricultural practices which favor nitrate enrichment and salinization due to irrigation water return flow. © 2016, Springer-Verlag Berlin Heidelberg

The geochemistry of Boron-rich groundwater of the Karlovassi Basin, Samos Island, Greece

The upper Miocene of Karlovassi Basin, Samos Island, Greece, contain continental evaporites such as colemanite, ulexite, celestite, gypsum and thenardite. These evaporites are related with volcanic tuffs, diagenetically altered in a saline-alkaline lake environment. The aim of the present paper is to: a) define the impact of the already known and possible buried borates and other evaporites to the geochemistry of the hydrogeological system of Karlovassi Basin, and; b) to assess the correlation between surface and underground evaporite deposits considering the spatial changes in the concentrations of the examined physicochemical parameters. Fieldwork, laboratory measurements and literature data revealed elevated boron values (2136-33012 μg/L) in the central part of Karlovassi Basin. In the same area, high amounts of strontium, sodium, lithium and sulfates also occur. It is proposed that these ions originate from the leaching of evaporites and authigenic minerals such as the Sr-rich clinoptilolite and the boron-bearing potassium feldspar. Boron values are abnormally high for freshwater aquifers, and are indicative of the presence of buried evaporites in the basin with unknown significance

Stan geochemiczny i oddziaływania między glebą a systemem wód podziemnych na obszarze Akrefnio, środkowa Grecja. Ocena zagrożeń dla ludzi i środowiska naturalnego

Totally 50 samples of groundwater and soil were collected from the area of Akrefnio (central Greece), in order to assess the geochemical status and the risk for humans and natural environment. The analytical results and processing of the initial data revealed that the main factors controlling hydrogeochemistry are the natural enrichment from calcareous substrate and the manmade pollution through extensive use of N-fertilizers. Soil geochemistry was mainly influenced by the occurrence of lateritic horizons, which gave raise to elevated concentrations of Ni and Cr in the majority of soil samples. Although most of the geochemical enrichment processes between soil and groundwater are common, the above geochemical systems don't seem to interact, and act most of the times independently. Risk assessment of natural and mankind environment revealed that groundwater is suitable for drinking but not for irrigation, due to high salinity. Finally, soils are highly polluted by Ni and Cr, and thus are inappropriate for the existing agricultural land uses.Pobrano 50 próbek gleby i wody gruntowej z obszaru Akrefnio (środkowa Grecja) do oceny stanu geochemicznego i zagrożeń ludzi i środowiska naturalnego. Wyniki analiz i przetworzenie danych ujawniły, że głównymi czynnikami hydrogeochemicznymi są zasilanie z wapiennego podłoża i antropogeniczne zanieczyszczenia, pochodzące z nadmiernego stosowania nawozów azotowych. Geochemia gleby podlegała silnym wpływom laterytowych poziomów, które zwiększały stężenie niklu i chromu w większości próbek glebowych. Choć większość procesów geochemicznych między glebą a wodami gruntowymi ma charakter powszechny, opisany system nie wykazywał interakcji, a jego elementy funkcjonowały w większości niezależnie. Ocena zagrożeń naturalnego środowiska wykazała, że woda gruntowa nadaje się do spożycia, ale nie do nawodnień z powodu silnego zasolenia. Gleby są w wysokim stopniu zanieczyszczone niklem i chromem, dlatego są nieodpowiednie do obecnego wykorzystania rolniczego

Assessing the hydrogeochemistry of groundwaters in ophiolite areas of Euboea Island, Greece, using multivariate statistical methods

Major ion and selected trace element compositions were analyzed in 102 groundwater samples from central and northern areas of Euboea Island, Greece, where both serpentinite dissolution and anthropogenic activities (agricultural) are in action. By integrating hydrogeochemical and two multivariate statistical methods, hierarchical cluster analysis (HCA) and principal component analysis (PCA), the chemistry of these groundwaters was assessed with the aim to understand the evolution of groundwater and assign the major processes that exert control on its composition. HCA classified the groundwater samples into three chemically distinct groups (C1-C3) according to their dominant chemical composition. These three clusters were further categorized by their electrical conductivity values: C1 (median EC: 480μS/cm), C2 (median EC: 608μS/cm), C3 (median EC: 1020μS/cm). PCA was performed to identify the underlying natural and anthropogenic processes affecting the chemistry of these groundwaters. The PCA results can be represented by two principal factors: (1) salinization by seawater intrusion and NO3- contamination; and (2) enrichment of groundwater with Mg2+, HCO3- and Cr following groundwater-serpentinite interaction. A third trivial component is associated with more local effects of the geological substrate. The three components of the PCA account for 70% of the total variance in the data. Dissolved Cr concentrations (up to 71μg/L) that rise environmental concerns are more pronounced in the groundwaters from the alluvial coastal area of Politika (C3 water samples). Results of this study demonstrate that appropriate measures should be taken to protect the vital groundwater resources in the alluvial coastal area including the regulation of the amount of chemical fertilizers applied to agricultural soils and the monitoring of groundwater pumping rates. © 2015 Elsevier B.V.

Hydrogeochemical characteristics and genetic implications of Edipsos thermal springs, north Euboea, Greece

Edipsos area, situated in northern Euboea, has been well known since ancient times for the existence of thermal springs. In order to assess the hydrogeochemical conditions, thermal and cold water samples were collected and analyzed by ICP method for major and trace elements. The results revealed the direct impact of seawater, a process which is strongly related to the major tectonic structures of the area. Seawater impact was confirmed by the Cl/Br and Na/Cl ionic ratios, as well as from statistical processing and graphical interpretation of the analytical results, which classified the sampled waters into three groups (two for cold waters and one for the thermal ones). Trace element ranges for thermal waters are: As (44-84 ppb), Pb (23-154 ppb), Ag (1-2 ppb), Mn (31-680 ppb), Cu (61-97 ppb), Cs (66-244 ppb), Se (0-76 ppb), Li (732-3269 ppb), Fe (0-1126 ppb), Sr (14000-34100 ppb), B (4300-9600 ppb).Compared with the chemical composition of other thermal springs from the Hellenic Volcanic Arc, Edipsos thermal waters are enriched in Ca2+, Na+, Cl-</ sup>, SO42-, Li, B and K+, reflecting the influence from seawater. Cold waters are free of heavy metals compared with other natural waters and are characterized by good quality based on the major element chemistry. Finally, several geothermometers were applied in order to assess the reservoir temperatures, but none of them appear to be applicable, mainly due to the impact of seawater on the initial hydrogeochemistry of the geothermal fluids

Design and implementation of a hybrid model based on two-layer decomposition method coupled with extreme learning machines to support real-time environmental monitoring of water quality parameters

Accurate prediction of water quality parameters plays a crucial and decisive role in environmental monitoring, ecological systems sustainability, human health, aquaculture and improved agricultural practices. In this study a new hybrid two-layer decomposition model based on the complete ensemble empirical mode decomposition algorithm with adaptive noise (CEEMDAN) and the variational mode decomposition (VMD) algorithm coupled with extreme learning machines (ELM) and also least square support vector machine (LSSVM) was designed to support real-time environmental monitoring of water quality parameters, i.e. chlorophyll-a (Chl-a) and dissolved oxygen (DO) in a Lake reservoir. Daily measurements of Chl-a and DO for June 2012–May 2013 were employed where the partial autocorrelation function was applied to screen the relevant inputs for the model construction. The variables were then split into training, validation and testing subsets where the first stage of the model testing captured the superiority of the ELM over the LSSVM algorithm. To improve these standalone predictive models, a second stage implemented a two-layer decomposition with the model inputs decomposed in the form of high and low frequency oscillations, represented by the intrinsic mode function (IMF) through the CEEMDAN algorithm. The highest frequency component, IMF1 was further decomposed with the VMD algorithm to segregate key model input features, leading to a two-layer hybrid VMD-CEEMDAN model. The VMD-CEEMDAN-ELM model was able to reduce the root mean square and the mean absolute error by about 14.04% and 7.12% for the Chl-a estimation and about 5.33% and 4.30% for the DO estimation, respectively, compared with the standalone counterparts. Overall, the developed methodology demonstrates the robustness of the two-phase VMD-CEEMDAN-ELM model in identifying and analyzing critical water quality parameters with a limited set of model construction data over daily horizons, and thus, to actively support environmental monitoring tasks, especially in case of high-frequency, and relatively complex, real-time datasets. © 201

Identifying potential effects of climate change on the development of water resources in Pinios River Basin, Central Greece

The aim of the present study is to assess the future spatial and temporal distribution of precipitation and temperature, and relate the corresponding change to water resources’ quantitative status in Pinios River Basin (PRB), Thessaly, Greece. For this purpose, data from four Regional Climate Models (RCMs) for the periods 2021–2100 driven by several General Circulation Models (GCMs) were collected and bias-correction was performed based on linear scaling method. The bias-correction was made based on monthly precipitation and temperature data collected for the period 1981–2000 from 57 meteorological stations in total. The results indicate a general trend according to which precipitation is decreasing whilst temperature is increasing to an extent that varies depending on each particular RCM–GCM output. On the average, annual precipitation change for the period 2021–2100 was about − 80 mm, ranging between − 149 and + 35 mm, while the corresponding change for temperature was 2.81 °C, ranging between 1.48 and 3.72 °C. The investigation of potential impacts to the water resources demonstrates that water availability is expected to be significantly decreased in the already water-stressed PRB. The water stresses identified are related to the potential decreasing trend in groundwater recharge and the increasing trend in irrigation demand, which constitutes the major water consumer in PRB