Learning objectives
to give knowledge and tools to the students for learning and intepretation of chemical and isotope composition of the waters: from sampling to data interpretation.
Course unit content
Concentration units. Italian and european water laws and regulations. Water composition and classification. Analytical methods, accuracy and precision of the data. Elements of thermodynamic: equilibria, saturation index, activity. Weathering processes and activity diagram. Chemical and isotope geothermometers. Isotope geochemistry: stable (18O/16O, 2H/1H, 34S/32S) e radiactive (3H) isotope. Water speciation and calculation software (PHREEQCI). Laboratory excercises on water software and/or analytical methods
Full programme
Terrestrial hydrosphere, units of measurement of concentrations, transformations between units of measurement. Water legislation. Definition of mineral, spring and drinking waters. Mineral water labeling. Characterizing parameters. Chemical and microbiological parameters. The hydrological cycle. Water classification. Major, minor and trace constituents. Electro-neutrality of solutions, example of calculation. Fixed residue and legal limits for the classification of water The TDS and classification based on the TDS. Classification of Marotta and Sica .: Classification of waters. Characterization and comparison diagrams. Definition and presentation of the different diagrams (Stiff, Langelier-Ludwig, Piper, etc.). The thermal waters of northern Tuscany and the Apennine front of the Po Valley. Genesis and evolution. Determination of Temperature. Parameters influenced by temperature. Zones of heterothermic and homothermic. Water classification by means of the temperature parameter. Silica geothermometers. Cationic geothermometers: K / Na, K / Mg. Water hardness. Determination of hardness by titration with EDTA. Calculation of hardness from the chemical composition. French, German and English degrees and conversion between them. Water sampling in rivers and lakes. Sampling mode. Labile parameters. The pH. Conductivity. Alkalinity. Analytical Methods: Ion Exchange Chromatography, Molecular Absorption Spectroscopy, Atomic Absorption Spectroscopy, ICP-AES Atomic Emission Spectroscopy, ICP-MS Quadrupole Spectroscopy and TIMS. Limits of Detection and Limits of Quantification. Precision and accuracy. International water standards. Isotopes, isotopic abundance of hydrogen and oxygen. Isotope fractionation. Vapor pressure and relation with the mass of the isotopes. Isotope ratios of light elements determined in isotopic geochemistry. Delta writing (). The reference standards for the different elements. The fractionation factor alpha () and relationship with equilibrium constant K and temperature. Isotope fractionation, Rayleigh equation, correlations with fractionation factor alpha (), delta () values. Variation of the isotopic composition of water vapor and liquid water with varying temperatures, with the residual vapor fraction (F). Latitude, altitude and continental effect. Global Meteoric Water Line, Primary and secondary evaporation and excess deuterium and correlation with air humidity. Equilibrium isotope and kinetic fractionation: effects on the slope of the precipitation line. Gradients 18O-altitude. Tritium: formation, half-life, unit of measurement, the "spring window", dating of the waters. Qualitative estimate of the age of the waters. Berner's zoneography of well water. High temperature water systems, isotopic composition of the water molecule, shifts from GMWL. "Andesitic" water. Thermodynamics: equilibrium of a reaction, Gibbs free energy, equilibrium constant, calculation of K from delta G ° of reaction, Vant's Hoff equation and calculation of K at the temperature of interest. Saturation index YES. Activity and activity coefficient.
Ionic force, definition and example of calculation. Calculation of the activity coefficient: application of the different equations (Debye-Huckel, Truesdell-Jones, Davies, Setchenow) as a function of the Ionic Force value. Variation of the activity coefficient with the ionic strength for ions in solution and zero valent species. Alteration of silicate minerals. Soil alteration profile. Composition of groundwaters interacting with silicate minerals. Acidification by CO2. Formation of oxalates. Alteration rate due to variation of the washout: formation of montmorillonite and its compositional variations, formation of kaolinite and gibbsite. Formation of diagenetic illite, influences on the permeability and porosity of arenaceous rocks.
Activity diagrams. Stability of the Gibbsite. Aluminum monomers and polymers in solution: activity diagrams. Alteration of silicate rocks and activity diagrams log (Ca2 + / H + 2) vs log (H4SiO4), log (K + / H +) vs log (H4SiO4), log (Mg2 + / H + 2) vs log (H4SiO4) and stability of Kaolinite, Gibbsite and Montmorillonite (Ca, Ca-Mg, Mg).
Exercise at the Analytical Chemistry Laboratory: sample preparation, calibration standards, calibration line, ICP-OES instrumentation.
Exercise at the Analytical Chemistry Laboratory: sample preparation, calibration standards, calibration line, instrumentation Ion chromatography on column, instrument description and analysis.
Exercise at the Computer Laboratory: use of software (Phreeqci_AqQa) for water speciation, activity determination, activity coefficients, saturation indices, mixing calculations, graphic representations for chemical classification.
Practice at the Wet Chemistry Laboratory: instruments for water sampling, calibration and use pH meter, conductivity meter, photometer and determination of chlorides.
Bibliography
Hydrogeochemistry: Appelo C.A.J., Postma D. (1994, 2007) Geochemistry, Groundwater and Pollution. Balkema
Kehew A.E. (2001) Applied Chemical Hydrogeology. Prentice Hall
Langmuir D. (1997) Aqueous Environmental Chemistry. Prentice Hall
Isotope geochemistry: Clark I., Fritz P. (1997) Environmental Isotopes in Hydrogeology. Lewis
Sharp Z. (2007) Principles of Stable Isotope Geochemistry. Pearson Prentice Hall
Geochemistry: Faure G. (1998) Principles and Application of Geochemistry. Prentice Hall
Venturelli G. (2003) Acque, Minerali e Ambiente. Pitagora
Software: PHREEQCI: http://wwwbrr.cr.usgs.gov/projects/GWC_coupled/phreeqc/ (freeware)
Teaching methods
frontal and laboratory lessons; use of geochemical software. Part of the exercises will be individual and practical in order to allow the student to independently accomplish a specific analytical procedure outlined in theory during the lessons.
Assessment methods and criteria
exercises; texts reading of books or scientific publications in the classroom; final oral exam
