Solution to Problem 9.5

Toluene [H_T = 0.28 >> 0.01] is waterside controlled
Lindane [H_L = 2.2 x 10^-5 << 0.01] is airside controlled
Napthalene [H_N = 0.04 0.01] is controlled by both air and water side conditions.

(a) Sketch the profile of C(z) for each chemical

b) Write an equation for the mass flux at the air-water interface for each chemical.
c) For each chemical determine the time at which only 5% of the original mass remains.

d) For which chemicals is the assumption of a uniform concentration within the bulk fluid appropriate?

The mixing time is, T_D = h²/(4Dt) = (1m)²/(4x0.001 m²s^-1) = 250 s. For every chemical T_D << T_5%,
so the assumption of well-mixed conditions in the lake are appropriate for each chemical.

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