An industrial accident inadvertently releases four chemical substances into a lake:

• The red substance is degraded in both the aerobic and the anaerobic layers.
• The orange substance is degraded in the anaerobic layer by a first-order reaction, but it is inert in the aerobic layer.
• The green substance is degraded in the aerobic layer, but not in the anaerobic one.
• The blue substance is completely inert.

The graph shows the concentration of all four substances over the entire depth of the lake, which ranges from $$z=0$$ to $$z=z_g$$ (depth of the ground).

Adjust the parameter α = to change the speed with which the substances decay.

z=0
z=zg
Aerobic zone
Anaerobic zone
Concentration
Depth