What does the unit ppb mean when applied to a contaminant in water? how does that differ

from the usage for air contaminants?

• the federal air quality standard for no2 for annual arithmetic mean is 100 μg/m3. what is the

corresponding value in ppmv? assume t = 293 k and p = 1 atmosphere.

• the maximum contaminant level for cadmium in drinking water is 0.005 mg/l. convert this

mass concentration to a mass fraction in units of parts per million (ppm).

problem

a manufacturer of rat poison in texas proposes to build a circular lagoon to concentrate the arsenic in

its rinse water by evaporation. the rinse water is produced at a rate of 10,000 gpd (gallons per day) and

contains 2.5 mg/l of arsenic. to reuse the water exiting the lagoon in the manufacturing process, it

must contain 10 mg/l arsenic. if the evaporation rate from an open water surface is 0.27 inch/day in

harlingen. texas, what should be the surface area of the lagoon? (note: arsenic does not evaporate but

remains in the liquid water).