Search results for "Waters"

showing 10 items of 281 documents

Thermomineral waters of Greece: geochemical characterization

2020

75 °C). In terms of pH most results vary from 5.5 to 823 °C) ii) warm (23 40 °C) iii) thermal (40 75 °C) and iv) hyperthermal (&gtfew springs show either very low pH (&lt10) proposing serpentinization processes. Regarding TDS concentrations collected waters can be subdivided into low salinity (up to 1.5 g/L) brackish (up to 20 g/L) and saline (up to 43 g/L). The medium high salinities can be justified by mixing with sea water and/or strong waterrock interaction processes. Isotope composition of O and H ranges from 12.7 to +2.7 ‰ SMOW and from 91 to +12 ‰ SMOW respectively and is generally comprised between the Global Meteoric Water Line and the East Mediterranean Meteoric Water Line. Only few water samples show a positive shift for δ18O possibly related to high temperature waterrock interaction processes. Carbon dioxide (18 997000 μmol/mol) or N2 (1100 989000 μmol/mol) or CH4 (&ltMany geothermal areas of Greece are located in regions affected by Miocene or Quaternary volcanism and in continental basins characterised by elevated heat flow. Moreover the majority of them is found along the coast as well as in islands of the Aegean Sea and thus thermal water is often brackish to saline due to marine intrusion into costal aquifer. In the present study almost 300 thermal and cold mineral water samples were collected along the Hellenic territory with their physicochemical parameters (temperature pH electrical conductivity and Eh) and the amount of bicarbonates (titration with 0.1N HCl) being determined in situ. Additionally gases found either in free or dissolved phase were sampled. Both water and gas samples were analysed at the INGVPa laboratories for major ions (Ion Chromatography) silica (Inductively Coupled Plasma Optical Emission Spectrometry) chemical composition of free and dissolved gases (Gas Chromatography) water isotopes (O and H) and carbon and helium isotopes of free and dissolved gases (Mass Spectrometry). The temperature of the investigated waters ranges from 6.5 to 98°C pH from 1.96 to 11.98 whilst Total Dissolved Solids (TDS) from 0.06 to 43 g/L. Based on the temperature parameter waters can be divided into four groups: i) cold (&lt0.5 913000 μmol/mol) are the prevailing gas species found in the studied sites. The δ13CCO2 values ranged from 20.1 to +8.5 ‰ whilst the isotope ratio of He from 0.21 to 6.71 R/RA.4) suggesting interaction with H2Srich gases or very high pH values (&gtSettore GEO/08 - Geochimica E Vulcanologia
researchProduct

Geochemistry of REE, Zr and HF in a wide range of pH and water composition: The Nevado del Ruiz volcano hydrothermal system (Colombia)

2015

International audience; The geochemical behaviour of Rare Earth Elements, Zr and Hf was investigated in the thermal waters of Nevado del Ruiz volcano system. A wide range of pH, between 1.0 and 8.8, characterizes these fluids. The acidic waters are sulphate dominated with different Cl/SO4 ratios. The important role of the pH and the ionic complexes for the distribution of REE, Zr and Hf in the aqueous phase was evidenced. The pH rules the precipitation of authigenic Fe and Al oxyhydroxides producing changes in REE, Zr, Hf amounts and strong anomalies of Cerium. The precipitation of alunite and jarosite removes LREE from the solution, changing the REE distribution in acidic waters.Y–Ho and Z…

Acidic waterGeochemistrychemistry.chemical_element[SDU.STU]Sciences of the Universe [physics]/Earth SciencesFractionationengineering.materialHydrothermal circulationGeochemistry and PetrologyRare earth elementJarositeIonic complexeZirconiumFe-Al oxyhydroxideAcidic waters; Fe-Al oxyhydroxides; Hafnium; Ionic complexes; Rare earth elements; Zirconium; Geochemistry and Petrology; GeologyGeologyYttriumAuthigenicAlunite6. Clean waterCeriumchemistry13. Climate actionengineeringZirconiumHafniumGeology
researchProduct

Main posterior watershed zone of the choroid

1989

The main posterior watershed zone of the choroid is located between the nasal edge of the optic disc and the fovea and represents the area situated between the territories supplied by the temporal and nasal posterior ciliary arteries. In the fluorescein angiographies of 800 normal subjects a watershed zone was not observed in 33.1% due to technical reasons and in 22.3% due to the simultaneous filling of the peripapillar and macular choriocapillaris. In the remaining 44.6% the watershed zone was well outlined: it was straddling the optic disc in about half of these cases and involved the temporal half of the optic disc and the close choroid in the other half. Very rarely the watershed zone i…

Adultgenetic structuresWatershed areaIndividualityGlaucomaReference ValuesPhysiology (medical)medicine.arterymedicineHumansFluorescein Angiographymedicine.diagnostic_testChoroidAnatomyMiddle Agedmedicine.diseaseFluorescein angiographyeye diseasesSensory SystemsCiliary arteriesVisual fieldOphthalmologymedicine.anatomical_structureBlood VesselsAnterior ischemic optic neuropathysense organsChoroidGeologyOptic discDocumenta Ophthalmologica
researchProduct

Supervised Classifications of Optical Water Types in Spanish Inland Waters

2022

Remote sensing of lake water quality assumes there is no universal method or algorithm that can be applied in a general way on all inland waters, which usually have different in-water components affecting their optical properties. Depending on the place and time of year, the lake dynamics, and the particular components of the water, non-tailor-designed algorithms can lead to large errors or lags in the quantification of the water quality parameters, such as the suspended mineral sediments, dissolved organic matter, and chlorophyll-a concentration. Selecting the most suitable algorithm for each type of water is not a simple matter. One way to make selecting the most suitable water quality al…

AiguaSentinel-2; optical water types; supervised classification; ocean color; inland watersGeneral Earth and Planetary Sciences
researchProduct

Methods of metal release assessment in soil water at anoxic sites

2006

Department of Geology, Vienna University, Vienna, Austria Metal mobility at contaminated sites can be assessed by soil water investigations or by leaching tests. Leaching tests are usually carried out in open contact with the atmosphere disregarding possible changes of redox conditions. This can affect the original metal speciation and distribution, particularly when anoxic samples are investigated. In this study, the applicability of common leaching tests (the German S4 test (S4), ammonium nitrate extraction (AmmN), and saturation soil extraction (SSE)) is tested for the assessment of zinc release from sulfide-bearing flotation residues of a former ore mine. Results are compared to soil so…

Ammonium nitrateEnvironmental engineeringLessivagechemistry.chemical_elementZincAquatic Sciencecomplex mixturesAnoxic waterschemistry.chemical_compoundchemistryNitrateEnvironmental chemistrySoil waterLeaching (pedology)Environmental ChemistryAmmoniumGeneral Environmental ScienceWater Science and TechnologyActa hydrochimica et hydrobiologica
researchProduct

Sediment quality assessment using Gmelinoides fasciatus and Monoporeia affinis (Amphipoda, Gammaridea) in the northeastern Baltic Sea

2013

Crustaceans in the order Amphipoda are sensitive organisms for the assessment of sediment quality. In this work we performed 10-day toxicity tests on muddy sediments collected from a total of 29 sites in the Gulf of Finland, the Gulf of Riga and the Gulf of Bothnia (northeastern Baltic Sea) using Baltic Sea species such as the native amphipod Monoporeia affinis (Bousfield, 1989) and the invasive amphipod Gmelinoides fasciatus (Stebbing, 1899), and also compared these results with those of bioassays carried out using the standard test species, laboratory-cultivated amphipod Hyalella azteca (Saussure, 1858). The sediment samples (three cm of the upper layer) were collected by a GEMAX Dual Cor…

AmphipodabiologyHyalella aztecaSedimentAquatic Sciencebiology.organism_classificationCrustaceanAnoxic watersFisheryCarcinologyOceanographyGammarideaAnimal Science and ZoologyMonoporeiaCrustaceana
researchProduct

Determination of the herbicide benfuresate by its photo-induced chemiluminescence using flow multicommutation methodology.

2007

The present paper deals with an analytical strategy based on coupling photo-induced chemiluminescence in a multicommutation continuous-flow methodology for the determination of the herbicide benfuresate. The solenoid valve inserted as small segments of the analyte solution was sequentially alternated with segments of the NaOH solution for adjusting the medium for the photodegradation. Both flow rates (sample and medium) were adjusted to required time for photodegradation, 90 s; and then, the resulting solution was also sequentially inserted as segments alternated with segments of the oxidizing solution system, hexacyanoferrate (III) in alkaline medium. The calibration range from 1 microg L(…

AnalyteCorrelation coefficientAnalytical chemistryFresh WaterAlkaliesAnalytical Chemistrylaw.inventionlawOxidizing agentWater Pollution ChemicalHumansPhotodegradationChemiluminescenceBenzofuransDetection limitReproducibilityChromatographyPhotolysisMolecular StructureChemistryHerbicidesVolumetric flow rateFlow Injection AnalysisLuminescent MeasurementsMineral WatersSulfonic AcidsAcidsTalanta
researchProduct

Simultaneous spectrophotometric determination of calcium and magnesium in mineral waters by means of multivariate partial least-squares regression.

1997

A method for simultaneous spectrophotometric determination of calcium and magnesium in mineral waters using multivariate calibration methods is proposed. The method is based on the development of the reaction between the analytes and Methylthymol Blue at pH 11. Two operational modes were used: static (spectral information) and flow injection (FI) (spectral and kinetic information). The selection of variables was studied. A series of synthetic solutions containing different concentrations of calcium and magnesium were used to check the prediction ability of the partial least-squares models. The method was applied to the analysis of mineral waters and the results were compared with those obta…

AnalyteMultivariate statisticsAnalytical chemistrychemistry.chemical_elementCalciumBiochemistrySensitivity and SpecificityAnalytical Chemistrychemistry.chemical_compoundSpectrophotometryPartial least squares regressionElectrochemistrymedicineEnvironmental ChemistryMagnesiumLeast-Squares AnalysisSpectroscopyMineralmedicine.diagnostic_testMagnesiumchemistrySpectrophotometryMultivariate AnalysisCalciumMineral WatersTriarylmethane dyeThe Analyst
researchProduct

An improved numerical solver of the 2D diffusive shallow waters equations over unstructured triangular meshes

2009

Analytical solution diffusive model numerical methods obtuse triangles shallow waters unstructured mesh
researchProduct

Green sulphur bacteria as a component of the photosynthetic plankton community in small dimictic humic lakes with an anoxic hypolimnion

2013

High bacteriochlorophyll (BChl) concentrations in the anoxic water layers of some humic lakes have indicated that green sulphur bacteria (GSB) may be ecologically significant. The abundance and spatial distribution of GSB were therefore addressed in 13 small humic lakes using fragment analysis and sequencing of PCR-amplified 16S rRNA genes. GSB were detected from lakes where the photosynthetically active radiation was at least 1.1 µE m �2 s �1 at the oxic� anoxic boundary layer. In these lakes, 13 to 42% of the 16S rRNA gene sequences of the anoxic water column were assigned to GSB. The spatial distribution of GSB was tightly correlated with the spectrophotometrically measured BChl concentr…

Aquatic SciencePlanktonBiologySpatial distributionPhotosynthesisAnoxic waterschemistry.chemical_compoundchemistryPhotosynthetically active radiationChlorophyllBotanyNaturvetenskapBacteriochlorophyllHypolimnionNatural SciencesEcology Evolution Behavior and Systematicsta119Aquatic Microbial Ecology
researchProduct