Environmental Science: Water Quality Downstream from a waste treatment plant the amount...

Environmental Science: Water Quality Downstream from a waste treatment plant the amount of dissolved oxygen in the water usually decreases for some distance (due to bacteria consuming the oxygen) and then increases (due to natural purification). A graph of the dissolved oxygen at various distances downstream looks like the curve below (known as the “oxygen sag”). The amount of dissolved oxygen is usually taken as a measure of the health of the river.

Suppose that the amount of dissolved oxygen x miles downstream is mpl (milligrams per liter) for 0 ≤ x ≤ 20. Use this formula to find the instantaneous rate of change of the dissolved oxygen:

a. 1 mile downstream.

b. 10 miles downstream.

Interpret the signs of your answers.