4.1 Zinc is an essential and beneficial element in body growth. Concentrations above 5 mg/L can cause a bitter astringent taste and opalescence in alkaline waters. The zinc concentration of U.S. drinking waters varies between 0.06 and 7.0 mg/L with a mean of 1.33 mg/L. Zinc most commonly enters the domestic water supply from deterioration of galvanized iron and dezincification of brass. Zinc in water also may result from industrial water pollution.3
1.1 These test methods cover the determination of zinc in water. Two test methods are given as follows:
| Test Method | Concentration Range | Sections |
| A—Atomic Absorption, Direct | 0.05 to 2 mg/L | |
| B—Atomic Absorption, | 20 to 200 μg/L |
1.3 These test methods have been used successfully with reagent grade water. See the specific test method for applicability to other matrices. It is the user's responsibility to assure the validity of these test methods in other matrices.