Environmental Engineering Reference
In-Depth Information
intentionally developed a simple mathematical format that required a min-
imum of measured parameters. He felt a balance must be struck between a
complex model few could afford to parameterize and the degree of accuracy
and precision required in its application (Karickhoff et al., 1979). Karickhoff
showed that for neutral hydrophobic contaminants (i.e., water solubilities
less than 10 -3 M ), sorption isotherms in the low loading limit are linear and
reversible. Their partition coefficients (K p ) were highly correlated to the
organic carbon content of the soils/sediments in this data set. Referencing
sorption to organic carbon content produced a partition coefficient to organic
carbon (K oc ) that was independent of other bulk sediment/soil parameters.
Karickhoff's (1981) “justifiable simplification” found even wider application
when he showed that K oc could be directly derived from the contaminants'
octanol-water partition coefficients.
Concurrently, Könemann and van Leeuwen (1980) showed a linear rela-
tionship between K oc and the partitioning of a series of chlorobenezenes from
sediments to lipid normalized benthic infaunal biomass. McFarland (1984)
synthesized information from Karickhoff and Könemann and van Leeuwen
and derived a relationship for TBP (McFarland and Clarke, 1986):
TBP = AF(C S /f OC )f L
where
AF = accumulation factor
C S = recalcitrant compound concentration in whole sediment
f OC = decimal fraction of organic carbon in sediment
f L = decimal fraction of lipid in targeted organism
Biota-sediment accumulation factors (BSAFs) have also been empirically
determined and used to describe the distribution of recalcitrant compounds
between lipid normalized biomass and organic carbon normalized sediment.
BSAF = (C T /f L )/(C S /f OC )
where
C T /f L = the lipid normalized contaminant tissue concentration
C S /f OC = the organic carbon normalized contaminant sediment
concentration
Initial TBP predictions, derived from an arbitrarily fixed AF of 4, were
shown to consistently overestimate polycyclic aromatic hydrocarbon (PAH)
bioaccumulation from contaminated sediments by factors ranging between
41 and 386 (McFarland, 1995). Precision and accuracy of TBP predictions
were improved to a factor of 10 when empirically derived BSAFs from one
field reference sediment contaminated with PAH were used to calculate TPB
for a second field sediment contaminated with PAH (Clarke and McFarland,
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