These drinking-water tests measure radioactivity, asbestos fibers and the inorganic forms of arsenic. Each test below names the EPA method and how the result is reported.
| Test | Method |
|---|---|
| Gross alpha and gross beta | EPA Method 900.0 |
| Radium-228 and combined radium | EPA Method 904.0 (radium-228); EPA Method 903.1 (radium-226) |
| Radon in water | No method number listed |
| Asbestos | EPA Method 100.2 |
| Arsenic speciation (arsenite and arsenate) | EPA Method 1632A |
Radioactivity
EPA Method 900.0: a measured volume of water is evaporated onto a planchet, and the alpha and beta particles given off by the dried residue are counted in a gas-flow proportional counter. The result is a screening measure of total radioactivity, reported in picocuries per liter (pCi/L); it does not identify the radionuclides.
EPA Method 904.0 for radium-228: radium is separated from the sample by co-precipitation with barium sulfate, and the actinium-228 that forms from radium-228 is separated and its beta activity counted. Combined radium-226 and radium-228 is also offered: radium-226 is measured by EPA Method 903.1, radon emanation. Radium is co-precipitated with barium sulfate, the precipitate is dissolved and sealed in a bubbler while radon-222 grows in from the radium-226, and the radon is then transferred to a scintillation cell and counted for alpha activity. The radium-226 and radium-228 results are added to give combined radium. Reported in pCi/L.
Radon-222 is a radioactive gas that forms as uranium in rock and soil decays and dissolves into ground water, so it matters mainly for wells and other ground-water supplies. Most of the risk comes from breathing radon released into indoor air when the water is used, with a smaller risk from drinking it. EPA proposed a drinking-water regulation for radon in 1999, for systems that use ground water, and has not published a final rule, so radon is not among the contaminants in the current national primary drinking water regulations. Radon in water is expressed in picocuries per liter (pCi/L). Radon escapes from water quickly, so contact us before sampling.
Asbestos and arsenic forms
EPA Method 100.2: the water is passed through a membrane filter, and the fibers collected are examined by transmission electron microscopy, which identifies asbestos by its shape, crystal structure and composition. Asbestos fibers longer than 10 µm are counted and reported as million fibers per liter (MFL).
EPA Method 1632A, hydride generation with quartz furnace atomic absorption: inorganic arsenic is converted to arsine gas, collected in a cold trap, and measured by atomic absorption in a heated quartz cell. Arsenite (As III) is measured under conditions where arsenate does not react; total inorganic arsenic is measured after the conditions are changed, and arsenate (As V) is the difference. Reported in µg/L. A total arsenic result from the metals tests does not show these forms.
The method numbers on this page follow the published EPA and Standard Methods designations. These references describe the methods; the TNI LAMS registry lists each method’s code and revision.
Questions about a sample or a method, call 360-967-7010 or email [email protected].
