If a manufacturer recommends 0.2 ppm elemental copper for algae control in a pond of 6.9 acre-feet, how much active ingredient is required?

To determine the amount of active ingredient needed for algae control, it is important to begin by converting the pond volume into gallons, as the recommended concentration is given in parts per million (ppm), which relates to mass per unit volume.

First, convert acre-feet to gallons. One acre-foot is approximately 325,851 gallons. For a pond with a volume of 6.9 acre-feet, the total volume in gallons would be calculated as follows:

6.9 acre-feet x 325,851 gallons/acre-foot = 2,253,891 gallons.

Next, knowing that 1 ppm corresponds to 1 milligram of solute per liter of solution, we can convert gallons to liters (since 1 gallon equals 3.78541 liters):

2,253,891 gallons x 3.78541 liters/gallon = 8,528,728 liters.

Now, at a concentration of 0.2 ppm elemental copper, we can determine the total mass needed. The formula to find the mass in milligrams is:

mass (mg) = concentration (ppm) x volume (liters).

So,

mass = 0.2 mg/L x 8,528,728 L = 1,