Calibration of the Gastrointestinal
Magnification
Model to Predict Maximum Biomagnification Potentials of Polychlorinated
Biphenyls in a Bird and Fish
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Abstract
The gastrointestinal magnification (GI-magnification)
model was
calibrated in ring doves and Japanese koi using matched data on dietary
assimilation and fecal depuration of polychlorinated biphenyls (PCBs).
Mass transport parameters describing PCB flux from gut contents to
organism (<i>D</i><sub>go</sub><sup>′</sup>; mol d<sup>–1</sup> Pa<sup>–1</sup>) and organism to gut contents (<i>D</i><sub>og</sub>;
mol d<sup>–1</sup> Pa<sup>–1</sup>) were quantified
to test the hypothesis that the ratio of these two terms approached
unity. For birds, <i>D</i><sub>go</sub><sup>′</sup>/<i>D</i><sub>og</sub> ranged
from 2.9 to 6.3 and for fish the ratios ranged from 0.7 to 3.1. In
both species, the ratio commonly exceeded 1. The GI-magnification
model was used to predict maximum PCB biomagnification factors (BMF<sub>max</sub>) for each species which ranged from 18.5 to 33.8 for ring
doves and 7.9 to 14.8 for Japanese koi. Chemical losses via respiration
reduced steady state biomagnification factor (BMF<sub>ss</sub>) estimates
by a negligible amount in birds, whereas for fish, predicted BMF<sub>ss</sub> decreased to values from 0.5 to 7.2. This study demonstrated
that chemical transfer efficiency during assimilation exceeds organism/feces
transfer which contributes to elevated PCB biomagnification potentials
in birds and fish. Combined with reduced losses of chemical across
respiratory surfaces, higher <i>D</i><sub>go</sub><sup>′</sup>/<i>D</i><sub>og</sub> ratios of birds contribute to elevated biomagnification
in birds over fish