Question

question 19
the ecological efficiency in a food chain is 20%. pollutant x is transferred from one trophic level to the next.
if the concentration of x on trophic level 4 is 1080 parts per million (ppm), with an efficiency of 60%, what will be the concentration of x on trophic level 1?
select one:
a. 120
b. 40
c. 80
d. 360

Explanation:

Step1: Recall the bio - magnification formula

The concentration of a pollutant in a food chain at a higher trophic level ($C_{2}$) can be calculated from the concentration at a lower trophic level ($C_{1}$) using the ecological efficiency ($E$) and the transfer factor ($T$). The formula for the transfer of a pollutant between trophic levels is $C_{2}=\frac{C_{1}\times T}{E}$. Here, $T = 0.2$ (20% transfer), $E=0.6$ (60% efficiency), and $C_{1} = 1080$ ppm.

Step2: Substitute the values into the formula

$C_{2}=\frac{1080\times0.2}{0.6}$. First, calculate $1080\times0.2 = 216$. Then, $\frac{216}{0.6}=360$ ppm.

Answer:

d. 360