An experimental analysis of the contribution of 210Po and of 210Po produced by 210Pb decay to the gross alpha-particle activity of water samples

The contribution of 210Po and of 210Po produced by 210Pb decay to the gross alpha-particle activity of water samples by U.S. Environmental Protection Agency Method 900.0 is investigated as a function of residue mass and geometry and time between sample collection and analysis. It is shown that these factors can cause the contribution to gross alpha-particle activity of 210Po to be up to 2.0 and 1.1 times the initial 210Po activity for grab and quarterly composite samples, respectively, and can cause the contribution to gross alpha-particle activity of 210Po from 210Pb decay to be up to 1.1 times and 1.5 times the 210Pb activity for grab and quarterly composite samples, respectively. It is also shown qualitatively that at least for some residues, there is a loss of polonium due to volatilization when the sample is heated over a flame.

An experimental analysis of the contribution of 228Ra progeny to the gross alpha-particle activity of water samples

The contribution of 228Ra progeny to the gross alpha-particle activity of water samples by EPA Method 900.0 is investigated as a function of residue mass and geometry and time between sample collection and analysis. It is shown that these factors can cause the contribution of 228Ra progeny to gross alpha-particle activity to be up to 2.2 times the initial 228Ra activity for grab samples and up to 3.5 times the initial 228Ra activity for quarterly composite samples when samples are held for the maximum 6-mo holding time. Thus, under some conditions, 228Ra, by itself, can cause a gross alpha-particle violation (>0.55 Bq L(-1)). Since 228Ra activity is already regulated, a gross alpha-particle activity violation that only exists because of the presence of 228Ra can be considered to be a false positive violation.

An experimental analysis of the contribution of 224Ra and 226Ra and progeny to the gross alpha-particle activity of water samples

The gross alpha-particle activity of water samples analyzed by EPA Method 900.0 is investigated as a function of residue mass and geometry, time between sample collection and analysis, and time between sample preparation and analysis for samples containing 224Ra, 212Pb, and 226Ra. It is shown that the gross alpha-particle activity due to 224Ra and its progeny can be up to 10 times the 224Ra activity at collection time and that due to 212Pb progeny can be up to 3 times the 212Pb activity at collection time. In samples with roughly equal activities of 224Ra and 226Ra analyzed soon after collection, it is shown that the gross alpha-particle activity is approximately constant with time because the decay of 224Ra and its progeny is offset by the ingrowth of 226Ra progeny.

An experimental analysis of some of the factors affecting gross alpha-particle activity with an emphasis on 226Ra and its progeny

This work presents an experimental investigation of the measurement of the gross alpha-particle activity of water samples by EPA Method 900.0. The residue produced in Method 900.0 is modeled by a BaSO4 precipitate distributed over a planchet. The dependence of the gross alpha-particle activity on the activity of Ra and its progeny, on the residue mass and geometry, and on the time between sample preparation and analysis is studied. It is shown that these factors can cause the gross alpha-particle activity of a sample to vary by more than a factor of three for replicate samples and to significantly overestimate the alpha activity of the residue. For a given sample geometry, the gross-alpha particle activity generally increases as the residue mass increases owing to the presence of the radium progeny.