An indirect way of measuring of secondary emission from ponds or large bodies of water used in waste treatment is to measure the concentration and velocity over the surface. The data can then be fitted to a model of the type presented.

In a typical experiment benzene concentration and velocity were measured at various locations above the water surface and the data are as follows.

Fit the data to the boundary-layer model and evaluate the rate of emission from the surface. \(D\) for benzene is \(0.077 \mathrm{~cm}^{2} / \mathrm{s}\) in air.
Usually the data are measured at about six points above the surface, but we use only two points in order to simplify the calculations.
Write a critique on this technique of secondary-emission measurement.

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Location (cm) Velocity (cm/s) Concentration (ng/l) 10 230 470 100 700 390