JEE Advanced levelNumerical answerDifficulty 3 of 3ev209
A river contains DDT at 0.0030 ppm (mg per kg of water). Plankton concentrate it 200-fold relative to water. Each of the three later trophic transfers (small fish, large fish, fish-eating bird) multiplies the concentration in the organisms by 7.5. Assume 1 ppm = 1 mg per kg of tissue. Calculate the mass of DDT, in mg, in 0.250 kg of body fat of the bird, if the fat has the same concentration as the bird's tissue calculated above. Give the answer to two decimal places.
Numerical answer type, answer in mg, tolerance 0.01.
Answer: 63.28 mg
Concentration in plankton =0.0030×200=0.60 ppm. After three transfers =0.60×7.53=253.125 ppm. Mass of DDT in 0.250 kg of fat =253.125×0.250=63.28 mg.