Please reference this text Separation Process Principles$3$rd edition

Chemical and Biochemical Operations

The concentration of benzene above ground is cs$.$ The concentration of benzene in the soil before the spill is c$0.$ Assuming Fick$$s second law holds.

To use Fick$$s second law to solve for the benzene concentration c$($z$,$t$),$ What are the initial and boundary conditions?

Initial condition: at t$=0$

Boundary conditions o At z$=0$

At z

Sketch the concentration profiles in the below figure to illustrate how the concentration of the benzene changes in the soil over time. Instructions: sketch three profiles at three different times: t$0,$ t$1,$ and t$2($t$2>$t$1>$t$0=0),$ label the time next to the profile