EOSC 430 · Aqueous Geochemistry

Quantitative approaches to practical aqueous geochemistry problems. Equilibrium thermodynamics, kinetics, complexation, oxidation reduction, cation exchange, sorption and partitioning of organics. Case Studies. [2-2-0] Prerequisite: Either (a) all of CHEM 111, CHEM 113 or (b) all of CHEM 121, CHEM 123 or (c) SCIE 001 or (d) CHEM 154. Corequisite: EOSC 329.

Course Availability & Schedule

Course Webpage

 Alternate year course

Odd year start – Term 1

Learning Goals

 

1) Analysis of groundwater geochemistry problems

  • Critically evaluate groundwater geochemical problems
  • Develop and articulate conceptual models, identify geochemical important processes
  • Postulate reasonable explanations for observations
  • Predict consequences of a change in geochemical conditions using quantitative methods
  • Design geochemical interventions to drive a system to a desired state (e.g., contaminant remediation)

 

Background knowledge

  • Recognition and identification of typical field conditions and common patterns
  • Dominant processes, elemental behavior

Instructors

Ulrich Mayer, Steve Atkin

Lecture Topics

The focus of this course is to provide a basic understanding of geochemical processes and their effect the evolution of natural and contaminated groundwater. Quantitative approaches to groundwater geochemistry problems are introduced and further discussed based on practical applications and case studies. Specific topics covered include hydrolysis, acid-base chemistry, the carbonate system, aqueous complexation, dissolution-precipitation, cation exchange, surface complexation, and inorganic and microbially-mediated oxidation-reduction reactions. Case studies include the dedolomitization of aquifers, the formation of uranium roll fronts, arsenic contamination in Bangladesh, trace metal mobility in mining waste environments, and geochemical aspects of groundwater remediation methods.

Topics

Week 1

Introduction to groundwater geochemistry
Groundwater systems
Groundwater geochemical data
Geochemical Processe
Global Fluxes - the big picture
Chemical analysis of groundwater samples
Presentation of geochemical data

Week 2

Review of geochemical principles
Mass balance: reactions and the tableau
Thermodynamics and equilibrium
Geochemical modeling: PHREEQC V.2

Week 3

Acid/base geochemistry and aqueous complexation
Acid base chemistry
Buffering concepts
ANC and alkalinity
Acid rain and response of catchments
pCpH diagrams

Week 4

Carbonate geochemistry:
Carbonate equilibria
Carbonate equilibria calculations
Open and closed carbonate systems

Week 5

Carbonate geochemistry:
Mixing of waters
Carbonate minerals
Open and closed system dissolution of calcite
Dedolomitization

Week 6

Mineral dissolution-precipitation
Major mineral groups
Saturation index
Solubility diagrams
Stability diagrams
Kinetically controlled mineral dissolution-precipitation
Mineral weathering
Solid solutions
Case Studies

Week 7

Adsorption, ion exchange, and surface complexation
Sorption models
Kd approach
Nonlinear isotherms
Cation exchange capacity
Ion exchange models

Week

Adsorption, ion exchange and surface complexation
Ion exchange, case studies and examples
Ion exchange, selectivity coefficients
Surface charge
Point of zero charge
Types of surface complexed species
Surface protonation and deprotonation
Surface complexation with metals
Surface complexation with ligands
Adsorption characteristics of metals and ligands

Week 9

Redox geochemistry
The tools to understand redox reactions
Redox-active elements
Redox potential
pC-pe diagrams

Week 10

Redox geochemistry
pe-pH diagrams
Stability of water
Construction of pe-pH diagrams
Redox sequence in natural groundwater systems

Week 11

Redox geochemistry
Redox sequence in contaminated groundwater systems
Microbial ecology of natural and contamianted groundwater systems

Week 12

Redox geochemistry
Acid rock drainage processes
Redox controls on groundwater in Bangladesh

Week 13

Application of geochemical principles to groundwater attenuation
Permeable reactive barriers
In-situ chemical oxidation
Natural attenuation

 

Labs

A number of exercises will involve the application of quantitative techniques introduced in the course largely based on case studies. Some of the assignments involve the use of a computer model (PHREEQC V3) to simplify the assessment of more complex geochemical systems. An introductory laboratory on the use of this model is also part of the course.