Stock flow model analysis
A company has applied for a permit to discharge up to 1000 kg/year of
baloneyum (By) into a river. Downstream from the discharge, the
water is used for crop irrigation and for drinking water. Your
agency specifies that the permit should be granted if the most
exposed person would receive a By dose of 0.1 mg/day or less.
▫ The river has an average flow rate of 100,000 liters per second (l/s).
▫ An average of 100 l/s are used for crop irrigation.
10% of the water used for irrigation is taken up by the crops.
▫ 1,000,000,000 kg of crops are produced annually.
This includes both the edible and inedible part of the plants.
By is distributed uniformly throughout the plants.
▫ The concentration of By in drinking water is the same as in the river.
(Water treatment does not remove By.)
▫ Your agency considers that the most exposed person will drink 2 l/day of
water and eat 1 kg/day of vegetables from these crops.
• Given this information, should your agency issue the permit or not?