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1. A1.7-kg adult osprey eats 0.08 kg/d of lake trout containing 0.25 ppm of Aroc

ID: 277015 • Letter: 1

Question

1. A1.7-kg adult osprey eats 0.08 kg/d of lake trout containing 0.25 ppm of Arochlor 1254 PCB. Assume that the eagle excretes all PCB congeners with a mean first-order rate constant of 0.015/day. (3 points) a. Estimate the steady-state total-PCB concentration in the osprey b. What is the bioaccumulation factor (BAF) between the trout trophic level and the osprey level? c. If the average sediment concentration of Arochlor 1254 is 65 Hg/kg in the lake where the osprey feeds, what is the overall BAF for the system as referenced to sediment (not aqueous) concentrations. (This approach is commonly used for highly hydrophobic compounds that are difficult or impossible to measure in water, but which can be detected in sediments.)

Explanation / Answer

a) Estimate the steady-state total-PCB concentration in the osprey

Rate of PCBs concentration in = 0.08 * 106 * 0.25 * 10-6 = 0.02 mg/day

Steady state:

Rate of PCBs concentration out = Rate of PCBs concentration in

k = 0.015 day-1

For a first order reaction:

k[PCBs] = Rate of PCBs concentration in

[PCBs] = 0.02/0.015 = 1.33 mg