Protocol for the Derivation of Environmental and Human ... - CCME

Appendix C
Q = 1/(1 + K a /[H + ]) [8]
where
K a = acidity constant
Substituting [7] and [8] into [6]:
Y = C w [(K oc × F oc /(1 + K a /[H + ]) + ? m ]
The additional information required to calculate the total soil concentration of a weak acid contaminant
in equilibrium with the desired water quality is therefore:
• soil pH,
• acidity constant of the contaminant, and
• partition coefficient for the non-ionized acid.
Organic contaminants that protonate to cationic forms (e.g., amines) cannot be accommodated by the
above treatment because, in soils, cations are competitively sorbed on colloids, which vary with soil
type.
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