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Understanding the Radioactive Ingrowth and Decay of Naturally Occurring Radioactive Materials in the Environment: An Analysis of Produced Fluids from the Marcellus Shale.

Nelson AW, Eitrheim ES, Knight AW, May D, Mehrhoff MA, Shannon R, Litman R, Burnett WC, Forbes TZ, Schultz MK - Environ. Health Perspect. (2015)

Bottom Line: However, natural radioactivity found in the large volumes of "produced fluids" generated by these technologies is emerging as an international environmental health concern.Specifically, we examined the use of high-purity germanium gamma spectrometry and isotope dilution alpha spectrometry to quantitate NORM.Accurate predictions of radioactivity concentrations are critical for estimating doses to potentially exposed individuals and the surrounding environment.

View Article: PubMed Central - PubMed

Affiliation: Interdisciplinary Human Toxicology Program, University of Iowa, Iowa City, Iowa, USA.

ABSTRACT

Background: The economic value of unconventional natural gas resources has stimulated rapid globalization of horizontal drilling and hydraulic fracturing. However, natural radioactivity found in the large volumes of "produced fluids" generated by these technologies is emerging as an international environmental health concern. Current assessments of the radioactivity concentration in liquid wastes focus on a single element-radium. However, the use of radium alone to predict radioactivity concentrations can greatly underestimate total levels.

Objective: We investigated the contribution to radioactivity concentrations from naturally occurring radioactive materials (NORM), including uranium, thorium, actinium, radium, lead, bismuth, and polonium isotopes, to the total radioactivity of hydraulic fracturing wastes.

Methods: For this study we used established methods and developed new methods designed to quantitate NORM of public health concern that may be enriched in complex brines from hydraulic fracturing wastes. Specifically, we examined the use of high-purity germanium gamma spectrometry and isotope dilution alpha spectrometry to quantitate NORM.

Results: We observed that radium decay products were initially absent from produced fluids due to differences in solubility. However, in systems closed to the release of gaseous radon, our model predicted that decay products will begin to ingrow immediately and (under these closed-system conditions) can contribute to an increase in the total radioactivity for more than 100 years.

Conclusions: Accurate predictions of radioactivity concentrations are critical for estimating doses to potentially exposed individuals and the surrounding environment. These predictions must include an understanding of the geochemistry, decay properties, and ingrowth kinetics of radium and its decay product radionuclides.

No MeSH data available.


Related in: MedlinePlus

Theoretical model of NORM partitioning and associated waste in Marcellus Shale based on HPGe gamma spectrometry and alpha spectrometry of produced fluids. Solid arrows indicate a radioactive decay or series of radioactive decays. Dashed arrows indicate a physical or chemical partitioning process.
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f3: Theoretical model of NORM partitioning and associated waste in Marcellus Shale based on HPGe gamma spectrometry and alpha spectrometry of produced fluids. Solid arrows indicate a radioactive decay or series of radioactive decays. Dashed arrows indicate a physical or chemical partitioning process.

Mentions: Radiochemical disequilibria and ingrowth. Radiochemical yields for the final methodology were Po (81 ± 6%), U (63 ± 8%), and Th (85 ± 9%). The observed concentrations of natural U (238U, 235U, 234U), and Th isotopes (234Th, 232Th, and 230Th) were exceedingly low (< 5 mBq/L). These levels represented < 0.001% of the 226Ra radioactivity concentration (670 ± 26 Bq/L; 186 keV peak) in the sample of produced fluids described previously (Nelson et al. 2014). Similarly, we found that the radioactivity concentrations of Ra decay products, including 228Th, 214Pb, 214Bi, 212Pb, 210Pb, 210Po, and 208Tl, were initially near detection limits (Figure 2A–D, Tables 1 and 2; see Supplemental Material, “Expanded methods, Polonium-210 ingrowth”). In contrast, subsequent analysis of the same sample of produced fluids over time revealed an increase in the radioactivity concentration of decay products 210Po and 228Th, which are supported by 226Ra and 228Ra, respectively (Figure 1; Figure 2A,B). Importantly, the storage drum was hermetically sealed between subsamplings for analysis of radioactive decay products to prevent the release of gaseous radon. Notably, under these conditions, the observed increase in radioactivity concentration of 210Po and 228Th followed an established radioactive ingrowth model (Bateman equation), which describes the ingrowth of decay products following a separation (radioactive disequilibrium) of decay products from the parent radionuclide at time zero (t0). From these observations we developed a theoretical model for the geochemical partitioning of NORM in the Marcellus Shale formation, within the context of hydraulic fracturing and associated waste disposal activities (Figure 3). This model serves as a guide for predicting the partitioning and radioactive ingrowth/decay of NORM in the environment surrounding unconventional drilling and hydraulic fracturing operations, as well as in the waste treatment and disposal setting. Importantly, the ultimate fate and transport of NORM in the surface and subsurface environment is site dependent and depends on the potential for release of radon gas; thus, the assessment of the ultimate fate and transport of NORM must be examined on an individual site basis.


Understanding the Radioactive Ingrowth and Decay of Naturally Occurring Radioactive Materials in the Environment: An Analysis of Produced Fluids from the Marcellus Shale.

Nelson AW, Eitrheim ES, Knight AW, May D, Mehrhoff MA, Shannon R, Litman R, Burnett WC, Forbes TZ, Schultz MK - Environ. Health Perspect. (2015)

Theoretical model of NORM partitioning and associated waste in Marcellus Shale based on HPGe gamma spectrometry and alpha spectrometry of produced fluids. Solid arrows indicate a radioactive decay or series of radioactive decays. Dashed arrows indicate a physical or chemical partitioning process.
© Copyright Policy - public-domain
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4492269&req=5

f3: Theoretical model of NORM partitioning and associated waste in Marcellus Shale based on HPGe gamma spectrometry and alpha spectrometry of produced fluids. Solid arrows indicate a radioactive decay or series of radioactive decays. Dashed arrows indicate a physical or chemical partitioning process.
Mentions: Radiochemical disequilibria and ingrowth. Radiochemical yields for the final methodology were Po (81 ± 6%), U (63 ± 8%), and Th (85 ± 9%). The observed concentrations of natural U (238U, 235U, 234U), and Th isotopes (234Th, 232Th, and 230Th) were exceedingly low (< 5 mBq/L). These levels represented < 0.001% of the 226Ra radioactivity concentration (670 ± 26 Bq/L; 186 keV peak) in the sample of produced fluids described previously (Nelson et al. 2014). Similarly, we found that the radioactivity concentrations of Ra decay products, including 228Th, 214Pb, 214Bi, 212Pb, 210Pb, 210Po, and 208Tl, were initially near detection limits (Figure 2A–D, Tables 1 and 2; see Supplemental Material, “Expanded methods, Polonium-210 ingrowth”). In contrast, subsequent analysis of the same sample of produced fluids over time revealed an increase in the radioactivity concentration of decay products 210Po and 228Th, which are supported by 226Ra and 228Ra, respectively (Figure 1; Figure 2A,B). Importantly, the storage drum was hermetically sealed between subsamplings for analysis of radioactive decay products to prevent the release of gaseous radon. Notably, under these conditions, the observed increase in radioactivity concentration of 210Po and 228Th followed an established radioactive ingrowth model (Bateman equation), which describes the ingrowth of decay products following a separation (radioactive disequilibrium) of decay products from the parent radionuclide at time zero (t0). From these observations we developed a theoretical model for the geochemical partitioning of NORM in the Marcellus Shale formation, within the context of hydraulic fracturing and associated waste disposal activities (Figure 3). This model serves as a guide for predicting the partitioning and radioactive ingrowth/decay of NORM in the environment surrounding unconventional drilling and hydraulic fracturing operations, as well as in the waste treatment and disposal setting. Importantly, the ultimate fate and transport of NORM in the surface and subsurface environment is site dependent and depends on the potential for release of radon gas; thus, the assessment of the ultimate fate and transport of NORM must be examined on an individual site basis.

Bottom Line: However, natural radioactivity found in the large volumes of "produced fluids" generated by these technologies is emerging as an international environmental health concern.Specifically, we examined the use of high-purity germanium gamma spectrometry and isotope dilution alpha spectrometry to quantitate NORM.Accurate predictions of radioactivity concentrations are critical for estimating doses to potentially exposed individuals and the surrounding environment.

View Article: PubMed Central - PubMed

Affiliation: Interdisciplinary Human Toxicology Program, University of Iowa, Iowa City, Iowa, USA.

ABSTRACT

Background: The economic value of unconventional natural gas resources has stimulated rapid globalization of horizontal drilling and hydraulic fracturing. However, natural radioactivity found in the large volumes of "produced fluids" generated by these technologies is emerging as an international environmental health concern. Current assessments of the radioactivity concentration in liquid wastes focus on a single element-radium. However, the use of radium alone to predict radioactivity concentrations can greatly underestimate total levels.

Objective: We investigated the contribution to radioactivity concentrations from naturally occurring radioactive materials (NORM), including uranium, thorium, actinium, radium, lead, bismuth, and polonium isotopes, to the total radioactivity of hydraulic fracturing wastes.

Methods: For this study we used established methods and developed new methods designed to quantitate NORM of public health concern that may be enriched in complex brines from hydraulic fracturing wastes. Specifically, we examined the use of high-purity germanium gamma spectrometry and isotope dilution alpha spectrometry to quantitate NORM.

Results: We observed that radium decay products were initially absent from produced fluids due to differences in solubility. However, in systems closed to the release of gaseous radon, our model predicted that decay products will begin to ingrow immediately and (under these closed-system conditions) can contribute to an increase in the total radioactivity for more than 100 years.

Conclusions: Accurate predictions of radioactivity concentrations are critical for estimating doses to potentially exposed individuals and the surrounding environment. These predictions must include an understanding of the geochemistry, decay properties, and ingrowth kinetics of radium and its decay product radionuclides.

No MeSH data available.


Related in: MedlinePlus