EPA-RCA: 9320: Radium-228 in groundwater
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Official Method Name
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Method 9320: Radium 228 |
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Current Revision
| September, 1986 |
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Media
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WATER |
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Instrumentation
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Beta Gas Proportional Counter |
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Method Subcategory
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Radiochemical |
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Method Source
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Citation
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Brief Method Summary
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The radium in the water sample is collected by coprecipitation with barium and lead sulfate and purified by reprecipitation from EDTA solution. Both radium-226 and radium-228 are collected in this manner. After a 36-hr ingrowth of actinium-228 from radium-228, the actinium-228 is carried on yttrium oxalate, purified and beta counted. If radium-226 is also desired, the activity in the supernatant can be reserved for coprecipitation on barium sulfate, dissolving in EDTA and storing for ingrowth in a sealed radon bubbler. |
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Scope and Application
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This method covers the measurement of radium-228 in ground water and, if desired, the determination of radium-226 on the same sample. If the level of radium-226 is above 3 pCi/L, the sample must also be measured for radium-228. This technique is devised so that the beta activity from actinium-228, which is produced by decay of radium-228, can be determined and related to the radium-228 that is present in the sample. To quantify actinium-228 and thus determine radium-228, the efficiency of the beta counter for measuring the very short half-lived actinium-228 (avg. beta energy of 0.404 keV) is to be calibrated with a beta source of comparable average beta energy. |
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Applicable Concentration Range
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Interferences
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As evidenced by the results of the performance studies, the presence of strontium-90 in the water sample gives a positive bias to the radium-228 activity measured. However, strontium-90 is not likely to be found in ground water, except possibly in monitoring wells around a radioactive burial site. Excess barium in the water sample might result in a falsely high chemical yield. |
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Quality Control Requirements
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Minimum of one blank per sample batch. Include one spike duplicate for every 10 samples. |
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Sample Handling
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Samples should be preserved when collected using nitric acid. |
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Maximum Holding Time
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Relative Cost
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$51 to $200 |
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Sample Preparation Methods
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