Methods and tools of Geochemistry

Methods and tools of Geochemistry

Instructors :CoefficientECTSHoursModule
F. CHABAUX
D. LEMARCHAND
P. STILLE
L. AQUELINA (Rennes)		1224required

Course description :

This unit digs deeper in the concepts already taught in the second year of the academic course "Water Geochemistry" by detailing isotopic and geochemical tools associated with: 1- the characterization of weathering and erosion fluxes or atmospheric deposits in continental hydrosystems ; 2- the way the chemical elements are transported in the Environment (including a few pollutants as arsenic, lead, selenium …) ; and 3- the characteristic transit times within the various compartments on a hydrosystem.

  • Origin and speciation of chemical elements. Elements stemming from natural or forced weathering and erosion. Nutrients. Speciation of these elements in the compartments on a hydrosystem.
  • Geochemical survey, isotopic signatures, isotopic fractionation.
  • Water dating. Characteristic times of weathering and erosion processes and of associated transfers. Cosmogenic elements, radionuclides.
  • Monitoring of natural organic matter in solution and stable suspensions. Origin, forms, ways of transport. Tracing of its evolution and evaluation of mean transit times (carbon isotopes, etc.)
  • Insights to conceptual and numerical modeling of geochemical transfers.

In addition to the content of this teaching unit and that of the unit "Soils, multiphase flow and complex transport" a few exercises aimed at coupling various mechanisms can be envisioned.  For example, one could couple the calculation of isotopic fractionations with a transport equation which would result in a modeling tool of water ages. Another realization could also simplify the speciation mechanisms of some elements, model them as a thermo-kinetics reaction then coupled with a multi-component transport model. The main idea supported by these exercises is to face the student with complex problems for which he is invited to propose simplifications and produce a tractable model easily implemented in a few hours on a spreadsheet (as is often the case in engineering where the purpose is less to provide pinpoint accuracy rather a rapid answer to urgent issues.)