Pollution

To work with the system, we will need to know several
things:
1. The volume of the lake (in m 3 ).
2. The flow rate or flux of each of the inputs and outputs (in
volume per time, m 3- sec -1 ).
3. The concentration of pollutant in each of the parts of the
system (in mass of pollutant per volume, kg-m -3 ).
Residence time: the amount of time that a unit of input will
spend in the reservoir before it gets removed as output
= mass of substance in reservoir (mass)
Flux (mass/time)
• Steady state: output = input
• input > output; buildup of substance in reservoir (e.g. many
pollution instances)
• output > input; depletion of substance in reservoir (e.g.
depletion of natural resources)