Aquatic%20Chemistry%20367%20Civil%20and%20Environmental%20Engineering

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Aquatic Chemistry 367Civil and Environmental
Engineering

• Meeting time MWF 1100-1150am
• Meeting room Abbott Auditorium in Pancoe
  Pavillion
• Instructor Jean-Francois Gaillard
• jf-gaillard_at_northwestern.edu
• Grader Amy Dahl
• a-dahl_at_northwestern.edu

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Species in water
Soluble Species
Suspended Particles
Soluble Species
Suspended Particles
Small Complexes
Small Complexes
Particles
Particles

Colloidal, aggregates

Colloidal, aggregates
e.g.,
Inorganic
e.g.,
Inorganic

Oxides (Al, Fe, Mn, Si)

Oxides (Al, Fe, Mn, Si)
Metal Complex
Metal Complex

Adsorption surface

Adsorption surface
Me(CO
)
Me(CO
)
y
-
y
-
complexation
complexation
3
n
3
n

Co
-
entrainment

Co
-
entrainment
Hydrated
Hydrated
Ion
Ion
Me
(H
O)
Me
(H
O)
n
n
2
n
2
n
Living Organisms
Living Organisms

Intra/extra
-
cellular

Intra/extra
-
cellular
Complexes with
Complexes with

Oligoelements

Oligoelements
Macromolecules
Macromolecules

Toxicity

Toxicity
e.g., Fulvic Acid

Defense Mechanisms
e.g., Fulvic Acid

Defense Mechanisms
Sediments
Sediments!
e.g.,
amorphous or crystalline solids
e.g.,
amorphous or crystalline solids (precipitates and
mineral formation)
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Species in water

• Dissolved ions
• Major Cations (Ca2, Na, Mg2, K, Fe2 or Fe3)
• Trace elements (Zn2, Cr3, Cu2, Cd2)
• Anions (HCO3-, F-, Cl-, NO3-, SO42-)
• Non-charged (SiO)
• Organic molecules (humic substances)
• http//www.ar.wroc.pl/weber/kwasy2.htm
• Particulate
• Organic matter
• Clays
• Oxides

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Chemical Reactions

• Acid-base chemistry
• H2CO3 ? H HCO3-
• Coordination chemistry
• Hg2 Cl- ? HgCl
• Precipitation and dissolution
• ZnS(s) ? Zn2 S2-
• Redox reactions
• 4Fe2 O2 4H ? 4Fe3 2H2O

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Thermodynamic explanation

• Assumes equilibrium of a reaction is reached
• Simplifies solving mathematical expressions of
  chemical systems
• Use an equilibrium constant, K, to describe ratio
  of products to reactants
• aA bB ? cC dD
• K CcDd/AaBb

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Chemical Accounting - Concentration

• Mass concentration
• Mass of substance/volume of solution
• mg/L or mg/L
• Mass of substance/mass of solution
• mg/kg ppm or mg/kg ppb
• When 1ml 1g (density 1)
• 1 mg/L 1 ppm and 1 mg/L 1 ppb

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Chemical Accounting - Concentration

• Molar concentration (M)
• MOST IMPORTANT!!!
• Molarity moles of solute per volume solution in
  liters
• Molality moles of solute per mass of solvent in
  kg

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Chemical Accounting - Concentration

• Normal concentration (N)
• 1N 1 equivalent per liter
• Based on ion charge
• Ca2 CO32- ? CaCO3(s)
• 2 equivalents per mol Ca2
• Based on Acid-base reaction
• H3PO4 ? 3H PO43-
• 3 equivalents per mol H3PO4
• Based on Redox reaction
• 4Fe2 O2 4H ? 4Fe3 2H2O
• 4 equivalents per mol O2

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Chemical Accounting

• Calculating concentrations of all species in a
  system based on
• Mass conservation of all chemical elements
• Reactions occurring in system
• Now we will have an EXAMPLE!

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Rules for tableau method

• Components must be independent no component
  should be expressible as a function of other
  components
• Reactions much also be independent no reaction
  may be obtained as a linear combination of others
• Number of components equals number of species
  minus the number of chemical reactions
• NC NS NR
• H2O and H should always be chosen as components
• Electroneutrality Condition
• All positive charges must equal negative charges