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Env Chemistry Test 3

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Bow Model: half-life for a simple, static system
t1/2 = 1.58 x 10-8 (Koc Cw/P) days Koc-soil org. carbon to water S- aq. solubility P- vapor pressure
Leaching Capacity
R = 1/ Kd(1-phi^2/3)ds R- leaching capacity Kd- soil/water conc. Ds- density of solids Phi- pore water fraction of the soil
Mobility Index
MI = log(SV/Koc) S- water solubility V- vapor pressure Koc- soil org. C to water
Estimating Koc from Kow
Koc = 0.66 Kow ^(1.03)
Fugacity
Tendency of a chemical to escape from a compartment of phase through a boundary layer. Measured in Pa (pascals) for gas
Fugacity and Z
Conc. = Zf M(mass) = Conc. Volume
Capacity Factor Z from PV= nRT
Z-air = 1/ RT (R = constant, T = K) Z-water = 1/H (H-Henry's constant)
Zair
1/RT
Zwater
1/H 1/(vap press, aq. solubility)
Zsoil
Ksorb(soil)/H
Zsediment
Ksorb/H
Zbiota
Kb/H
Kb
[Biota]/ [Water] flipid/Kow
Ksorb
[solid]/ [water] 0.41foc Kow
Kow
[octanol]/[water]
Henry's Law
H = partial pressure of air/ conc. in water H = Pa/ moles cubic meters H units- Pa m^3 mole^-1
As pH increases, Cation Exchange Capacity (CEC)(Increases/Decreases)
Increases
Measurement of CEC in Lab
Saturate with NH4+, Wash with Na+, measure NH4+ released
Rule of Thumb for Cation Exchange Capacity
1/2 X% clay + 2X% organic carbon = mEq/100g
Soil Horizons
O- organic layer A- topsoil E- leaching zone B- subsoil C- soil parent material R- bedrock
Freundlich equation
Cs = Kd Cw^n Cs- organic compound in solid phase (mg/kg) Cw- dissolved organic compound (mg/L) Kd- Cs/Cw^n n- empirically determined
Charge of Organic Residues in soil
Positive at low pH, Negative at high pH
Gas Constant- R Standard Temp
R- 0.0821 L*atm/mol K K- 298
f for a system
f = Mtotal/ SUM ZiVi
Mi =
Mi = f ZiVi
Ci =
Ci = Mi/Vi

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