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Page Title:
Step 3: Food chain modeling (Cont.) |
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 BSAF = (Ca/Fl)/(Cs/Foc)
(1)
The final concentration of a bioaccumulative compound in wet-weight fish
tissue, Ca, is expressed as the bioaccumulation through the sediment pathway as:
Ca = (Cs/Foc) H BSAF H Fl
(2)
where
Cs =
average sediment exposure concentration for biota (calculated,
see below)
BSAF =
as calculated from site-specific data; data from the Tier III
testing; or literature values (site-specific data are preferable)
Fl and Foc are defined as above.
The term, Cs, can be calculated as:
Cs = Cd H Fa + Co H (1-Fa)
(3)
where
Cd
=
sediment concentration in the disposal site (projected or
measured)
Co
=
sediment concentration outside the disposal site (measured)
Fa
=
fraction of time the organism spends foraging in the disposal
site area.
Note that Fa will be 1 when the foraging area is equal to or less than the disposal
site area and the area of influence. When the foraging area is greater than the
disposal site area:
Fa = Ad/Af
(4)
where
Ad
=
area of the disposal site and area of influence
Af
=
foraging area of the receptor.
The ratio, Fa, may have to be adjusted based on site-specific data. For example,
disturbance at the disposal site may increase the attractiveness of the site for a
foraging species, causing Af to approach the value of Ad.
56
Chapter 3 Ecological Exposure Assessment
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