AN EXPERIMENTAL ANALYSIS OF THE CONTRIBUTION OF 224Ra AND 226Ra AND PROGENY TO THE GROSS ALPHA-PARTICLE ACTIVITY OF WATER SAMPLES

Arndt, Michael; West, Lynn E.

doi:10.1097/01.hp.0000303107.20899.4a

Cited by 6 publications

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“…This worked to indicate the presence of 210 Po in Nevada because radium isotopes were not present. Ingrowth of alpha‐emitting progeny of 226 Ra significantly increases the activity on a planchet, reaching a maximum at about 30 d (Arndt and West 2008b); however, the daughter product 222 Rn is volatile and can be lost, so the actual increase may be unpredictable. GAR can be relatively constant with time in samples having comparable activities of 226 Ra and 224 Ra because decay of 224 Ra and its progeny is offset by ingrowth of 226 Ra and its progeny (Arndt and West 2008b).…”

Section: Discussionmentioning

confidence: 99%

“…Ingrowth of alpha‐emitting progeny of 226 Ra significantly increases the activity on a planchet, reaching a maximum at about 30 d (Arndt and West 2008b); however, the daughter product 222 Rn is volatile and can be lost, so the actual increase may be unpredictable. GAR can be relatively constant with time in samples having comparable activities of 226 Ra and 224 Ra because decay of 224 Ra and its progeny is offset by ingrowth of 226 Ra and its progeny (Arndt and West 2008b). Additional information on the co‐occurrence of 226 Ra, 224 Ra, and 210 Po in the environment is needed; however, these results indicate that under some circumstances archiving planchets and recounting them if the adjusted GAR significantly exceeds the MCL could quickly provide information about the cause of the exceedance.…”

Section: Discussionmentioning

confidence: 99%

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210Po in Nevada Groundwater and Its Relation to Gross Alpha Radioactivity

Seiler

2011

Ground Water

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Polonium-210 ((210) Po) is a highly toxic alpha emitter that is rarely found in groundwater at activities exceeding 1 pCi/L. (210) Po activities in 63 domestic and public-supply wells in Lahontan Valley in Churchill County in northern Nevada, United States, ranged from 0.01 ± 0.005 to 178 ± 16 pCi/L with a median activity of 2.88 pCi/L. Wells with high (210) Po activities had low dissolved oxygen concentrations (less than 0.1 mg/L) and commonly had pH greater than 9. Lead-210 activities are low and aqueous (210) Po is unsupported by (210) Pb, indicating that the (210) Po is mobilized from aquifer sediments. The only significant contributors to alpha particle activity in Lahontan Valley groundwater are (234/238) U, (222) Rn, and (210) Po. Radon-222 activities were below 1000 pCi/L and were uncorrelated with (210) Po activity. The only applicable drinking water standard for (210) Po in the United States is the adjusted gross alpha radioactivity (GAR) standard of 15 pCi/L. (210) Po was not volatile in a Nevada well, but volatile (210) Po has been reported in a Florida well. Additional information on the volatility of (210) Po is needed because GAR is an inappropriate method to screen for volatile radionuclides. About 25% of the samples had (210) Po activities that exceed the level associated with a lifetime total cancer risk of 1× 10(-4) (1.1 pCi/L) without exceeding the GAR standard. In cases where the 72-h GAR exceeds the uranium activity by more than 5 to 10 pCi/L, an analysis to rule out the presence of (210) Po may be justified to protect human health even though the maximum contaminant level for adjusted GAR is not exceeded.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

210Po in Nevada Groundwater and Its Relation to Gross Alpha Radioactivity

Seiler

2011

Ground Water

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“…An additional limitation of the analytical data used here is the complications of the gross alpha measurement resulting from variations in the radiochemical compositions of groundwater. It is well established that the measured gross alpha activities of waters depend on the timing of the analysis relative to the collection date, specifically within the first 30 days of analysis (Arndt, 2010; Arndt & West, 2007, 2008a, 2008b, 2008c; Parsa, 1997). Certain short‐lived nuclides in the uranium and thorium decay chains that are the primary sources of alpha activity decay rapidly, leading to changes in the gross alpha activity over time.…”

Section: Resultsmentioning

confidence: 99%

The importance of uranium isotope composition for gross alpha activity regulation

Scott¹,

Plechacek

Krinke³

2023

AWWA Water Science

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Uranium is a regulated contaminant (maximum contaminant level [MCL] 30 μg/L) that contributes to the gross alpha activity of groundwater. The adjusted gross alpha activity (MCL 15 pCi/L) is determined by subtracting the total uranium activity from the measured gross alpha activity. U.S. water utilities can use mass-based and radiochemical analysis methods for compliance monitoring of uranium. Mass-based measurements use a conversion factor of 0.67 pCi/μg of uranium to calculate the adjusted gross alpha activity. This conversion factor assumes that the activity of 234 U equals 238 U. Here, we present two decades of uranium isotope data measured by alpha spectrometry that shows 234 U activity typically exceeds 238 U. Using mass-based measurements, the total uranium activity is biased low causing artificial exceedances of the adjusted gross alpha activity. Therefore, water utilities with gross alpha activities >15 pCi/L should utilize radiochemical analyses for uranium for the most accurate calculation of adjusted gross alpha activity.alpha spectrometry, gross alpha activity, groundwater, uranium isotope ratios | INTRODUCTIONUranium is regulated by the United States Environmental Protection Agency (EPA) due to its toxicological properties (Dinocourt et al., 2015;Selden et al., 2009;Zamora et al., 1998). The radionuclides rule was updated in 2000 to include a uranium maximum contaminant level (MCL) of 30 μg/L (US EPA, 2015). The radionuclides rule also addresses gross alpha activity. When the gross alpha activity is measured above 15 pCi/L, analysis of uranium is required to determine the adjusted gross alpha activity (gross alpha minus the uranium and radon activities). Establishing compliance with the MCL requires four consecutive quarterly samples, and initial compliance is based on the running average of these four initial samples. Any exceedance of the MCL during this period or in subsequent sampling efforts triggers additional quarterly monitoring. Ultimately, any entry point in a drinking water distribution system must demonstrate four consecutive quarterly samples below the MCL to comply with the radionuclides rule for adjusted gross alpha activity. Because total uranium activity is subtracted from the gross alpha activity for compliance monitoring, quantification of the total uranium activity is a critical factor for adhering to this regulation.Both radiochemical and mass-based measurements are approved for compliance monitoring of uranium under federal rule when this analysis is triggered by a

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“…This was achieved varying proportionately the amount of both carriers (1 to 2 mL of Ba and Fe carriers; stoichiometric residues) as well as varying but not proportionally (non-stoichiometric residues). The recoveries of 210 Pb,210 Bi and 210 Po, using a 3.5-y old 210 Pb standard (see Appendix C for the information of the standard), and Th (using a 230 Th standard), were checked using the purification procedure, and only obtaining BaSO 4 (Arndt and West, 2008) with 1mL of barium carrier. The residues containing BaSO 4 were counted immediately following preparation in α-β mode using the gas flow proportional counter (counting time: 300 min).…”

Section: Purification Proceduresmentioning

confidence: 99%

“…To measure the two efficiencies of the 224 Ra decay chain using the model reported by Arndt and West (2008), three conditions must hold for the Ba(Ra)SO 4 residues:…”

Section: Determination Of the Efficiencies From 224 Ra And Its Daughtersmentioning

confidence: 99%

Optimization of alpha emitter's determination in water. Behavior of radionuclides in water treatment plants

Montaña Guerra

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La determinació de l’índex alfa total en aigües és d’interès per ser un dels paràmetres inclòs en la legislació nacional e internacional associada a la qualitat de l’aigua per al consum humà. Aquest índex informa de la concentració d’emissors alfa continguts en l’aigua referits a un patró emissor alfa. Concretament en el nostre país, el control de la qualitat de l’aigua està regulat pel Reial Decret 140/2003. La determinació de l’índex d’alfa total en aigües és un assaig aparentment senzill, però a conseqüència de la variabilitat isotòpica que pot presentar una aigua i els procediments utilitzats, es poden obtenir resultats molt diferents, inclús en ordres de magnitud. A més a més, en certs casos el valor de l’índex alfa total no concorda amb el valor obtingut al sumar les activitats dels emissors alfa determinats en la mostra d’aigua. Per tot això es considera necessari dur a terme un estudi experimental, en el qual es determinin tots els possibles factors que influeixin en la variabilitat dels resultats i realitzar un procediment suficientment detallat en el qual s’estableixi tant l’ interval de validació com les condicions més adequades d’utilització, de forma que es pugui garantir que el resultat que s’obté sigui el més representatiu possible i que aquesta variabilitat romanent es tingui en compte en la determinació de la incertesa associable al resultat. Per una altra banda, a causa de la gran importància de l’aigua i les cada cop més exigents disposicions legals en quant a la depuració d’aigües residuals i tractament d’aigua potable, la construcció d’estacions de tractaments han anat incrementant notablement en els últims anys en un gran nombre de països. Com a conseqüència, grans quantitats de residus sòlids o llots son generats cada any com a subproducte d’aquestes plantes de tractament, per als quals s’apliquen diferents alternatives d’aprofitament i eliminació. Durant els processos habituals de tractament per a l’obtenció d’aigua potable i de depuració d’aigua residual, els isòtops radioactius es poden distribuir en les diferents etapes dels cicles de tractament, com les resines d’intercanvi, carbó actiu, filtres, membranes, materials absorbents i finalment en els subproductes produïts (fangs o llots), on es pot concentrar-se un percentatge elevat d’isòtops radioactius. Les aigües més afectades per la radioactivitat natural son les aigües d’aqüífers subterranis, ja que els processos de circulació lenta afavoreixen la seva incorporació. Els isòtops presents generalment a les aigües són els isòtops naturals d’Urani i Radi, 210Pb, 210Po, 222Rn i el 40K. També existeix la possibilitat de contaminació amb isòtops d’origen artificial que provenen de la indústria nuclear i de les probes nuclears. Per tant es considera d’interès realitzar un estudi detallat de la distribució dels isòtops radioactius en les diferents fases dels processos de potabilització i depuració convencionals o amb nous mètodes i en els subproductes generats per tal de poder valorar el possible impacte radiològic associat a la potabilització i reutilització de les aigües i dels subproductes. Gross alpha activity measurement is one of the simplest radioanalytical procedures which are widely applied as screening techniques in the fields of radioecology, environmental monitoring and industrial applications. It is used as the first step to perform a radiological characterization of drinking water. According to the WHO guidelines (2011), this screening parameter must be measured in drinking water to ensure that it is safe for consumption. Different methods are used to measure gross alpha activity. Two of them, the classic ones, are based on evaporation (EPA, 1980) or co-precipitation (EPA, 1984) of the sample, using either a gas proportional counter or a solid scintillator detector. Another alternative method based on concentration of the sample and measurement by liquid scintillation counting (ASTM, 1996), is being increasingly used. The gross alpha activity of a water sample is an estimate of the actual alpha activity of the water sample (excluding radon). However, it is usually considered that gross alpha activity must be very close to the sum of alpha emitter activities, though in general this is not the case. There are many other factors (e.g., alpha particle energies, calibration standard used, time elapsed from sample preparation to measurement and variability of the results between methods) that affect the gross alpha measurement causing major differences between the gross alpha activity values and the sum of the activities of the main alpha emitters. For this reason, we propose to conduct an eminently experimental study to determine most of the possible factors that may be involved in the above mentioned variability of the results. In addition, we intend to propose a detailed procedure on that basis to establish both their range of validity and the most suitable conditions for their use, thereby ensuring: (A) that the result obtained is the most representative of the sample's real total alpha activity; (B) that it is subject to the lowest technically possible variability; and (C) that this remaining variability is taken into account in determining the uncertainty associated with the result. In this context, we propose to study these aforementioned considerations using the co-precipitation method. Aditionally, given the problems with the scarcity and quality of water, the implementation of water treatment plants has been significantly increasing over the last years in several countries. Consequently, large quantities of solid wastes or sludge are generated every year which can be re-used for different applications. These solid wastes may contain all kind of pollutants, including significant levels of radioactivity. For these reasons, it is considered important studying the occurrence and behavior of radioactivity in water treatment plants. Although radioactivity in water treatment plants has been studied by some authors, we propose an original work analyzing the radioactive temporal evolution in different water treatment plants in which drinking and wastewater are treated. These plants have been selected taking into account both variations in water source and the treatment applied. This thesis contributes to these goals by analyzing the factors that affect the gross alpha measurement, involving an optimization and validation of the co-precipitation method and studying the behavior of radionuclides in water treatment plants. To this end, Part I provides a comprehensive analysis for the optimization and validation of the gross alpha activity determination using the co-precipitation method. Then, in Part II, we present a set of case studies related to the radionuclide behavior and the temporal evolution of the radioactivity in different drinking water and wastewater treatment plants.

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AN EXPERIMENTAL ANALYSIS OF THE CONTRIBUTION OF 224Ra AND 226Ra AND PROGENY TO THE GROSS ALPHA-PARTICLE ACTIVITY OF WATER SAMPLES

Cited by 6 publications

References 6 publications

210Po in Nevada Groundwater and Its Relation to Gross Alpha Radioactivity

210Po in Nevada Groundwater and Its Relation to Gross Alpha Radioactivity

The importance of uranium isotope composition for gross alpha activity regulation

Optimization of alpha emitter's determination in water. Behavior of radionuclides in water treatment plants

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