Estimation of the Distribution of PCBs in the Environment Polychlorinated biphenyls (PCBs) were manufactured as a liquid transformer oil. Due to leakage, PCBs are now found throughout the environment, and this long-lived chemical represents a health hazard. PCBs have been found to be present

Question

Estimation of the Distribution of PCBs in the Environment

Polychlorinated biphenyls (PCBs) were manufactured as a liquid transformer oil. Due to leakage, PCBs are now found throughout the environment, and this long-lived chemical represents a health hazard. PCBs have been found to be present in the St. Lawrence River at concentrations of about 0.3 ppb (parts per billion by weight). Estimate the likely concentration of PCBs in fish in this river. The average octanol-water partition coefficient for PCBs is

[latex] \log _{10} K_{ OW , PCB }=5.5 [/latex]

Accepted Answer

From Eq. 12.5-9, we have

[latex]K_{ BW , i }\left[\frac{\frac{ g _{ i }}{ m _{ B }^{3}}}{\frac{ g _{ i }}{ m _{ W }^{3}}} ight]=w_{ B } K_{ OW , i }[/latex] (12.5-9)

[latex]K_{ BW , PCB }=w_{ B } K_{ OW , PCB }=0.05 imes 10^{5.5}=1.58 imes 10^{4}[/latex]

Therefore,

[latex]\begin{aligned}C_{ B , PCB } &=K_{ BW , PCB } imes C_{ W , PCB } \&=1.58 imes 10^{4} imes 0.3 ppb \&=4740 ppb =4.74 ppm\end{aligned}[/latex]

Actual field testing has found the PCB concentration in eels in the St. Lawrence River to be 7.9 ppm.

Comment

The PCB concentration of eels in this river is a factor of 26 300 higher than the PCB concentration in the river water. The very simple phase equilibrium model for the distribution of the chemical used here is able to predict this very large bioconcentration effect to within a factor of 2.

Question 12.5.2: Estimation of the Distribution of PCBs in the Environment P...

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