Now that you have a grasp on modeling the input to a system, let's use the module to determine output concentrations by going through an example problem. This is probably the best way to get familiar with what the program can do for you, and how to use it.
Problem: A fisherman was participating in his favorite activity (fishing, of course!) at his favorite spot at the local reservoir, right where the only inlet stream empties into the reservoir.
Unfortunately, he ran out of gas.
Fortunately, he had a spare tank.
Unfortunately, while he was carrying the spare gas to his outboard motor, he tripped and dropped the tank overboard. As a result, 10 gallons of gasoline almost instantaneously were distributed to the 898,800 gallon reservoir at its well-mixed inlet.
Fortunately, he was an honest and intelligent fisherman who told the appropriate authorities about what had happened.
Unfortunately, by the time the fisherman contacted the appropriate authorities, and by the time the authorities shut off the flow exiting the reservoir, four days had passed. What the authorities are concerned about is the amount of gasoline that escaped the reservoir. If 1,000,000 mg of gasoline escaped, the concentration in the exiting stream will be too high for acceptable standards (not that any amount is actually "acceptable") and very expensive measures will have to be taken to clean up the stream. If less than that escaped, then they only have to concern themselves with cleaning up the reservoir.
Question: How much gasoline still remains in the reservoir, and will the exiting stream have to be remediated?
In order to find the answer, we first should decide how we plan to model the input (i.e., the gasoline spill). Should we model it as