2.1. Initial Conditions and Mass Accumulation

Try these first

1. 1.

   Define mass balance in your own words.

   Hint

   Think about how inputs and outputs relate.

2. 2.

   What is evaporation?

   Hint

   Consider what happens to water in a pot on the stove.

3. 3.

   What does the mass balance equation express?

   • Rate of Input = Rate of Output
   • Rate of Accumulation = Rate in - Rate out
   • Rate of Change = Mass Transfer

   Hint

   Focus on the relationship between what's coming in and going out.

4. 4.

   True or False: Evaporation plays no role in the mass balance of pollutants.

   • True
   • False

   Hint

   Remember how pollutants can enter the air.

5. 5.

   A factory continuously admits 500 kg of a pollutant every week into a lake while 200 kg are evaporated. Calculate the total mass of the pollutant after 4 weeks and discuss the implications.

   Hint

   Use the mass balance equation to track inputs and outputs.

6. 6.

   If the lake has an initial concentration of 4400 kg of a pollutant and it is diluted by a rainfall of 1000 cubic meters with a clean water influx, what happens to the concentration?

   Hint

   Consider how dilution works when additional water is introduced.