In 2000, the U.S. Environmental Protection Agency (USEPA) promulgated a revised final regulation for radionuclides in drinking water. This
rule retained the maximum contaminant level (MCL) at 5 pCi/L for combined Ra226/Ra228 but
requires separate monitoring requirements for Ra228. Previously, analysis for Ra228 was
required only when Ra226 measurement was greater than 3 pCi/L.
With the promulgation of the Radionuclide Rule and completion of the first round of required
monitoring, many utilities throughout the country who were previously in compliance have
found themselves now uncertain of their compliance status as a result of the added compliance
monitoring parameters. In some regions radionuclide activities from groundwater supplies at the
same site appear to vary by more than two fold over time. This may be due to natural variability
in concentrations of some of the radionuclides, but it is also likely due to issues related to method
and laboratory variability. To address this issue MWH evaluated compliance data from a
number of utilities who have done repeat monitoring over time and then designed and conducted
a blind interlaboratory evaluation of performance for routine samples among 5 multi-state
certified labs. This interlab study was designed to address both intralab variation among blind
replicate samples at levels near the MCL for radium 226, radium 228 and gross alpha activity,
along with assessing laboratory precision and accuracy, and equally important, to examine the
interlab variability among well qualified laboratories for the same samples. Participating
laboratories were not aware that the study was a blind proficiency test, so samples were
processed in the same way that normal compliance samples were processed. A total of 14
samples were submitted to each laboratory in several discrete batches. Each batch consisted of
several replicates and also some Youden pairs to determine the single lab precision at applicable
concentration ranges for compliance assessment and historical data.
Results of the interlab study demonstrate that while Radium-226 measurements appear to be both
accurate and precise, even at low levels, radium-228 analysis and gross alpha is much less
rugged, resulting in potential false positives and false negatives for compliance determinations. Includes 8 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 280 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 17 |
| Published : | 11/01/2007 |
