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J. J. Mortvedt - One of the best experts on this subject based on the ideXlab platform.
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plant and soil relationships of uranium and thorium Decay Series radionuclides a review
Journal of Environmental Quality, 1994Co-Authors: J. J. MortvedtAbstract:The behavior of radionuclides of the uranium (U) and thorium (Th) Decay Series in terrestrial systems is of interest because of environmental effects of mining and disposal activities related to nuclear power plant fuels. The soil-plant relationships of U, Th, and polonium (Pb), and some other daughter radionuclides, notably radium ({sup 226}Ra), are not well understood. Most studies have been concerned with relative uptake of these radionuclides by various plant species. Plant concentrations have been related to total contents of these radionuclides in the soil as a plant/soil concentration ratio (CR), even though the fraction of these radionuclides, which may be available to plants, is not well known. These CR values have been used to predict transport of radionuclides and other elements of interest through the food chain as well as for other purpose including biogeochemical exploration for U. Little information is available on uptake and transport mechanisms of radionuclides in plants. However, the mechanisms relating to Ca uptake and translocation in plants may be similar to those of some radionuclides, especially {sup 226}Ra. Son chemical reactions of these radionuclides also have not been studied as well as those of plant nutrients, although knowledge of the effects of soil pH,more » soil texture, and organic matter content on uptake, as well as mobility in soil of these radionuclides, has been gained in recent years. 45 refs., 13 tabs.« less
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Plant and Soil Relationships of Uranium and Thorium Decay Series Radionuclides—A Review
Journal of Environmental Quality, 1994Co-Authors: J. J. MortvedtAbstract:The behavior of radionuclides of the uranium (U) and thorium (Th) Decay Series in terrestrial systems is of interest because of environmental effects of mining and disposal activities related to nuclear power plant fuels. The soil-plant relationships of U, Th, and polonium (Pb), and some other daughter radionuclides, notably radium ({sup 226}Ra), are not well understood. Most studies have been concerned with relative uptake of these radionuclides by various plant species. Plant concentrations have been related to total contents of these radionuclides in the soil as a plant/soil concentration ratio (CR), even though the fraction of these radionuclides, which may be available to plants, is not well known. These CR values have been used to predict transport of radionuclides and other elements of interest through the food chain as well as for other purpose including biogeochemical exploration for U. Little information is available on uptake and transport mechanisms of radionuclides in plants. However, the mechanisms relating to Ca uptake and translocation in plants may be similar to those of some radionuclides, especially {sup 226}Ra. Son chemical reactions of these radionuclides also have not been studied as well as those of plant nutrients, although knowledge of the effects of soil pH,more » soil texture, and organic matter content on uptake, as well as mobility in soil of these radionuclides, has been gained in recent years. 45 refs., 13 tabs.« less
Travis L. Mcling - One of the best experts on this subject based on the ideXlab platform.
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in situ radionuclide transport and preferential groundwater flows at ineel idaho Decay Series disequilibrium studies
Geochimica et Cosmochimica Acta, 2000Co-Authors: Shangde Luo, Robert C. Roback, Michael T. Murrell, Travis L. MclingAbstract:Uranium and thorium-Decay Series disequilibria in groundwater occur as a result of water-rock interactions, and they provide site-specific, natural analog information for assessment of in-situ, long-term migration of radionuclides in the far field of a nuclear waste disposal site. In this study, a mass balance model was used to relate the Decay-Series radionuclide distributions among solution, sorbed and solid phases in an aquifer system to processes of water transport, sorption-desorption, dissolution-precipitation, radioactive ingrowth-Decay, and α recoil. Isotopes of U (238U, 234U), Th (232Th, 230Th, 228Th, 234Th), Ra (226Ra, 228Ra, 224Ra), and Rn (222Rn) were measured in 23 groundwater samples collected from a basaltic aquifer at the Idaho National Engineering and Environmental Laboratory (INEEL), Idaho. The results show that groundwater activities of Th and Ra isotopes are 2–4 orders lower than those of their U progenitors which average 1.35 ± 0.40 dpm 238U/L, with 234U/238U ratios of ∼1.6–3.0. 222Rn activities range from 20 to 500 dpm/L. Modeling of the observed disequilibria places the following constraints on the time scale of radionuclide migration and water-rock interaction at INEEL: (1) Time for sorption is minutes for Ra and Th; time for desorption is days for Ra and years for Th; and time for precipitation is days for Th, years for Ra, and centuries for U. (2) Retardation factors due to sorption average >106 for 232Th, ∼104 for 226Ra, and ∼103 for 238U. (3) Dissolution rates of rocks are ∼70 to 800 mg/L/y. (4) Ages of groundwater range from <10 to 100 years. Contours of groundwater age, as well as spatial patterns of radionuclide disequilibria, delineate two north-south preferential flow pathways and two stagnated locales. Relatively high rates of dissolution and precipitation and α-recoil of 222Rn occur near the groundwater recharging sites as well as in the major flow pathways. Decay of the sorbed parent radionuclides (e.g., 226Ra and 228Ra) on micro-fracture surfaces constitutes an important source of their daughter (222Rn and 228Th) activities in groundwater.
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In-situ radionuclide transport and preferential groundwater flows at INEEL (Idaho): Decay-Series disequilibrium studies
Geochimica et Cosmochimica Acta, 2000Co-Authors: Shangde Luo, Robert C. Roback, Michael T. Murrell, Travis L. MclingAbstract:Uranium and thorium-Decay Series disequilibria in groundwater occur as a result of water-rock interactions, and they provide site-specific, natural analog information for assessment of in-situ, long-term migration of radionuclides in the far field of a nuclear waste disposal site. In this study, a mass balance model was used to relate the Decay-Series radionuclide distributions among solution, sorbed and solid phases in an aquifer system to processes of water transport, sorption-desorption, dissolution-precipitation, radioactive ingrowth-Decay, and α recoil. Isotopes of U (238U, 234U), Th (232Th, 230Th, 228Th, 234Th), Ra (226Ra, 228Ra, 224Ra), and Rn (222Rn) were measured in 23 groundwater samples collected from a basaltic aquifer at the Idaho National Engineering and Environmental Laboratory (INEEL), Idaho. The results show that groundwater activities of Th and Ra isotopes are 2–4 orders lower than those of their U progenitors which average 1.35 ± 0.40 dpm 238U/L, with 234U/238U ratios of ∼1.6–3.0. 222Rn activities range from 20 to 500 dpm/L. Modeling of the observed disequilibria places the following constraints on the time scale of radionuclide migration and water-rock interaction at INEEL: (1) Time for sorption is minutes for Ra and Th; time for desorption is days for Ra and years for Th; and time for precipitation is days for Th, years for Ra, and centuries for U. (2) Retardation factors due to sorption average >106 for 232Th, ∼104 for 226Ra, and ∼103 for 238U. (3) Dissolution rates of rocks are ∼70 to 800 mg/L/y. (4) Ages of groundwater range from
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Decay Series disequilibrium study of in situ long term radionuclide transport in water rock systems
MRS Proceedings, 1999Co-Authors: Shangde Luo, Robert C. Roback, K U Tehlung, Micheal Murrell, Travis L. MclingAbstract:Uranium and thorium-Series disequilibrium in nature permits the determination of many insitu physico-chemical, geologic and hydrologic variables that control the long-term migration of radionuclides in geologic systems. It also provides site-specific, natural analog information valuable to the assessment of geologic disposal of nuclear wastes. In this study, a model that relates the Decay-Series radioisotope distributions among solution, sorbed and solid phases in water-rock systems to processes of water transport, sorption-desorption, dissolutionprecipitation, radioactive ingrowth-Decay, and α recoil is discussed and applied to a basaltic aquifer at the Idaho National Engineering and Environmental Laboratory (INEEL), Idaho.
Shangde Luo - One of the best experts on this subject based on the ideXlab platform.
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Chapter 9 Ocean Circulation/Mixing Studies with Decay-Series Isotopes
Radioactivity in the Environment, 2008Co-Authors: Shangde LuoAbstract:Publisher Summary This chapter summarizes the efforts to use naturally occurring U- and Th-Decay Series nuclides as tracers of ocean circulation/mixing in open-ocean and coastal environments. The Decay-Series isotopes that have been exploited for ocean mixing studies are the four radium isotopes ( 226 Ra, 228 Ra, 224 Ra, and 223 Ra), 222 Rn, and 227 Ac. In addition, particle-reactive radionuclides ( 230 Th, 231 Pa, and 210 Pb) have been used to constrain basin-wide water residence or ventilation times. Isotopes of radium, 222 Rn, and 227 Ac have been used to trace mixing and circulation in the ocean because of their relatively high solubility in seawater and suitable half-lives. 226 Ra has a suitable radioactive mean-life, ∼2,300y, for large-scale oceanic mixing studies. The small-scale temporal and spatial variability generally associated with coastal mixing processes accentuates the integrating power of the 228 Ra tracer. Along with the three other radium isotopes of the “radium quartet,” 228 Ra is steadily input to coastal waters by desorption and diffusion from shelf, estuarine, and/or marsh sediments and through submarine groundwater discharge. Water close to the shore thus has a continual supply of these Ra isotopes despite their short Decay lives. Produced in seawater by the Decay of 226 Ra, 222 Rn in the ocean has activities equal to those of 226 Ra except in regions of the air–sea and sediment–sea interfaces. Exceptionally high apparent vertical mixing has been observed in deep-ocean passages, where the interplay between strong bottom water flows, manganese nodule occurrence, and high standing crop of excess 222 Rn is much in evidence. Several studies have explored the use of 227 Ac for tracing basin-wide circulation and mixing on decadal time-scales. The potential of 227 Ac as a tracer appears to lie chiefly in assessing diapycnal mixing in the deep sea.
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chapter 9 ocean circulation mixing studies with Decay Series isotopes
Radioactivity in the Environment, 2008Co-Authors: Shangde LuoAbstract:Publisher Summary This chapter summarizes the efforts to use naturally occurring U- and Th-Decay Series nuclides as tracers of ocean circulation/mixing in open-ocean and coastal environments. The Decay-Series isotopes that have been exploited for ocean mixing studies are the four radium isotopes ( 226 Ra, 228 Ra, 224 Ra, and 223 Ra), 222 Rn, and 227 Ac. In addition, particle-reactive radionuclides ( 230 Th, 231 Pa, and 210 Pb) have been used to constrain basin-wide water residence or ventilation times. Isotopes of radium, 222 Rn, and 227 Ac have been used to trace mixing and circulation in the ocean because of their relatively high solubility in seawater and suitable half-lives. 226 Ra has a suitable radioactive mean-life, ∼2,300y, for large-scale oceanic mixing studies. The small-scale temporal and spatial variability generally associated with coastal mixing processes accentuates the integrating power of the 228 Ra tracer. Along with the three other radium isotopes of the “radium quartet,” 228 Ra is steadily input to coastal waters by desorption and diffusion from shelf, estuarine, and/or marsh sediments and through submarine groundwater discharge. Water close to the shore thus has a continual supply of these Ra isotopes despite their short Decay lives. Produced in seawater by the Decay of 226 Ra, 222 Rn in the ocean has activities equal to those of 226 Ra except in regions of the air–sea and sediment–sea interfaces. Exceptionally high apparent vertical mixing has been observed in deep-ocean passages, where the interplay between strong bottom water flows, manganese nodule occurrence, and high standing crop of excess 222 Rn is much in evidence. Several studies have explored the use of 227 Ac for tracing basin-wide circulation and mixing on decadal time-scales. The potential of 227 Ac as a tracer appears to lie chiefly in assessing diapycnal mixing in the deep sea.
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in situ radionuclide transport and preferential groundwater flows at ineel idaho Decay Series disequilibrium studies
Geochimica et Cosmochimica Acta, 2000Co-Authors: Shangde Luo, Robert C. Roback, Michael T. Murrell, Travis L. MclingAbstract:Uranium and thorium-Decay Series disequilibria in groundwater occur as a result of water-rock interactions, and they provide site-specific, natural analog information for assessment of in-situ, long-term migration of radionuclides in the far field of a nuclear waste disposal site. In this study, a mass balance model was used to relate the Decay-Series radionuclide distributions among solution, sorbed and solid phases in an aquifer system to processes of water transport, sorption-desorption, dissolution-precipitation, radioactive ingrowth-Decay, and α recoil. Isotopes of U (238U, 234U), Th (232Th, 230Th, 228Th, 234Th), Ra (226Ra, 228Ra, 224Ra), and Rn (222Rn) were measured in 23 groundwater samples collected from a basaltic aquifer at the Idaho National Engineering and Environmental Laboratory (INEEL), Idaho. The results show that groundwater activities of Th and Ra isotopes are 2–4 orders lower than those of their U progenitors which average 1.35 ± 0.40 dpm 238U/L, with 234U/238U ratios of ∼1.6–3.0. 222Rn activities range from 20 to 500 dpm/L. Modeling of the observed disequilibria places the following constraints on the time scale of radionuclide migration and water-rock interaction at INEEL: (1) Time for sorption is minutes for Ra and Th; time for desorption is days for Ra and years for Th; and time for precipitation is days for Th, years for Ra, and centuries for U. (2) Retardation factors due to sorption average >106 for 232Th, ∼104 for 226Ra, and ∼103 for 238U. (3) Dissolution rates of rocks are ∼70 to 800 mg/L/y. (4) Ages of groundwater range from <10 to 100 years. Contours of groundwater age, as well as spatial patterns of radionuclide disequilibria, delineate two north-south preferential flow pathways and two stagnated locales. Relatively high rates of dissolution and precipitation and α-recoil of 222Rn occur near the groundwater recharging sites as well as in the major flow pathways. Decay of the sorbed parent radionuclides (e.g., 226Ra and 228Ra) on micro-fracture surfaces constitutes an important source of their daughter (222Rn and 228Th) activities in groundwater.
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In-situ radionuclide transport and preferential groundwater flows at INEEL (Idaho): Decay-Series disequilibrium studies
Geochimica et Cosmochimica Acta, 2000Co-Authors: Shangde Luo, Robert C. Roback, Michael T. Murrell, Travis L. MclingAbstract:Uranium and thorium-Decay Series disequilibria in groundwater occur as a result of water-rock interactions, and they provide site-specific, natural analog information for assessment of in-situ, long-term migration of radionuclides in the far field of a nuclear waste disposal site. In this study, a mass balance model was used to relate the Decay-Series radionuclide distributions among solution, sorbed and solid phases in an aquifer system to processes of water transport, sorption-desorption, dissolution-precipitation, radioactive ingrowth-Decay, and α recoil. Isotopes of U (238U, 234U), Th (232Th, 230Th, 228Th, 234Th), Ra (226Ra, 228Ra, 224Ra), and Rn (222Rn) were measured in 23 groundwater samples collected from a basaltic aquifer at the Idaho National Engineering and Environmental Laboratory (INEEL), Idaho. The results show that groundwater activities of Th and Ra isotopes are 2–4 orders lower than those of their U progenitors which average 1.35 ± 0.40 dpm 238U/L, with 234U/238U ratios of ∼1.6–3.0. 222Rn activities range from 20 to 500 dpm/L. Modeling of the observed disequilibria places the following constraints on the time scale of radionuclide migration and water-rock interaction at INEEL: (1) Time for sorption is minutes for Ra and Th; time for desorption is days for Ra and years for Th; and time for precipitation is days for Th, years for Ra, and centuries for U. (2) Retardation factors due to sorption average >106 for 232Th, ∼104 for 226Ra, and ∼103 for 238U. (3) Dissolution rates of rocks are ∼70 to 800 mg/L/y. (4) Ages of groundwater range from
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Decay Series disequilibrium study of in situ long term radionuclide transport in water rock systems
MRS Proceedings, 1999Co-Authors: Shangde Luo, Robert C. Roback, K U Tehlung, Micheal Murrell, Travis L. MclingAbstract:Uranium and thorium-Series disequilibrium in nature permits the determination of many insitu physico-chemical, geologic and hydrologic variables that control the long-term migration of radionuclides in geologic systems. It also provides site-specific, natural analog information valuable to the assessment of geologic disposal of nuclear wastes. In this study, a model that relates the Decay-Series radioisotope distributions among solution, sorbed and solid phases in water-rock systems to processes of water transport, sorption-desorption, dissolutionprecipitation, radioactive ingrowth-Decay, and α recoil is discussed and applied to a basaltic aquifer at the Idaho National Engineering and Environmental Laboratory (INEEL), Idaho.
Wouter Schroeyers - One of the best experts on this subject based on the ideXlab platform.
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measurement of radioactivity in building materials problems encountered caused by possible disequilibrium in natural Decay Series
Construction and Building Materials, 2018Co-Authors: Boguslaw Michalik, Wouter SchroeyersAbstract:Abstract The determination of the activity concentration of naturally occurring radionuclides in construction materials is based on the principles of gamma-spectrometry. Gamma spectrometry is a comparative method and therefore includes many parameters that are specific to the test sample and measurement circumstances. Consequently, several of the testing conditions must be verified prior to testing and/or require correction to obtain accurate results. Besides problems encountered during the measurement, the interpretation of the results and calculation of the activity indices, needed for material classification, may lead to significant mistakes. Current regulation in the European Union requires to calculate an activity concentration index (index I) using the activity concentration of 226Ra, 232Th and 40K. Not all of these radionuclides are directly measurable by gamma spectrometry and, to determine the index, additional assumptions have to be made about secular equilibrium in uranium and thorium Decay Series. These assumptions are often not valid in case of NORM (Naturally Occurring Radioactive Materials) where long term lack of secular equilibrium in the uranium and/or thorium Decay Series is often observed. As a consequence, this may result in an underestimation or overestimation of the index. The article discusses specific disequilibrium situations in building materials. Sources for potential inaccurate determinations and misinterpretation are identified and practical mitigation options are proposed.
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Measurement of radioactivity in building materials – Problems encountered caused by possible disequilibrium in natural Decay Series
Construction and Building Materials, 2018Co-Authors: Boguslaw Michalik, Wouter SchroeyersAbstract:Abstract The determination of the activity concentration of naturally occurring radionuclides in construction materials is based on the principles of gamma-spectrometry. Gamma spectrometry is a comparative method and therefore includes many parameters that are specific to the test sample and measurement circumstances. Consequently, several of the testing conditions must be verified prior to testing and/or require correction to obtain accurate results. Besides problems encountered during the measurement, the interpretation of the results and calculation of the activity indices, needed for material classification, may lead to significant mistakes. Current regulation in the European Union requires to calculate an activity concentration index (index I) using the activity concentration of 226Ra, 232Th and 40K. Not all of these radionuclides are directly measurable by gamma spectrometry and, to determine the index, additional assumptions have to be made about secular equilibrium in uranium and thorium Decay Series. These assumptions are often not valid in case of NORM (Naturally Occurring Radioactive Materials) where long term lack of secular equilibrium in the uranium and/or thorium Decay Series is often observed. As a consequence, this may result in an underestimation or overestimation of the index. The article discusses specific disequilibrium situations in building materials. Sources for potential inaccurate determinations and misinterpretation are identified and practical mitigation options are proposed.
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Gamma exposure from building materials – A dose model with expanded gamma lines from naturally occurring radionuclides applicable in non-standard rooms
Construction and Building Materials, 2018Co-Authors: Tom Croymans, Cristina Nuccetelli, Rosabianca Trevisi, Sonja Schreurs, Federica Leonardi, Wouter SchroeyersAbstract:Abstract Building materials are a significant source of gamma rays exposure due to the presence of naturally occurring radionuclides. In order to protect the public from harmful radiation, the European Basic Safety Standards (Council directive 2013/59/Euratom) (European Council, 2014) introduced a one-size-fits-all building(s) (materials) activity concentration index (ACI) based on a limited set of gamma lines. The ACI is considered “as a conservative screening tool for identifying materials that may cause the reference level (i.e. 1 mSv/y) laid down in article 75(1) to be exceeded”. Regarding calculation of dose, many factors such as density and thickness of the building material, as well as factors relating to the type of building, and the gamma emission data need to be taking into account to ensure accurate radiation protection. In this study the implementation of an expanded set of 1845 gamma lines, related to the Decay Series of 238U, 235U and 232Th as well as to 40K, into the calculation method of Markkanen (1995), is discussed. The expanded calculation method is called the Expanded Gamma Dose Assessment (EGDA) model. The total gamma emission intensity increased from 2.12 to 2.41 and from 2.41 to 3.04 for respectively the 238U and 232Th Decay Series. In case of 40K a decrease from 0.107 to 0.106 is observed. The 235U Decay Series is added, having a gamma emission intensity of 3.1. In a standard concrete room, the absorbed dose rates in air (DA) per unit of activity concentration of 0.849, 0.256, 1.08, 0.0767 nGy/h per Bq/kg are observed. The use of weighted average gamma lines increased the DA with 6.5% and 1% for respectively the 238U and 232Th Decay Series. A decrease of 4.5% is observed in the DA of 235U Decay Series when using the weighted average gamma lines in comparison to its non-averaged variant. The sensitivity of the EGDA model for density, wall thickness, presence of windows and doors and room size is investigated. Finally, a comparison of the index and dose calculations relevant for the dose assessment within the European legislative framework applicable towards building materials is performed. In cases where the ACI and density and thickness corrected dose calculation of Nuccetelli et al. (2015) cannot provide guidance, the EGDA allows performing more accurate dose assessment calculations leading to effective doses which can be several 100 µSv/y lower.
W. C. Burnett - One of the best experts on this subject based on the ideXlab platform.
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the distribution of uranium and thorium Decay Series radionuclides in the environment a review
Journal of Environmental Quality, 1994Co-Authors: J. B. Cowart, W. C. BurnettAbstract:Natural radioactivity has played an indispensable role in the development of the earth to the form and shape that we now observe. Energy from radioactivity powers the large-scale processes that move the continents and cycle the elements. Most of the energy due to radioactivity comes from members of the three Decay-Series, two of which are parented by isotopes of uranium, {sup 238}U and {sup 235}U, and one by {sup 232}Th. These Decay-Series cascade to produce radioactive offspring such as Ra, Rn, and Po, but the ultimate fate of all members of these Series is to end as a stable isotope of Pb. Rocks or minerals that provide sites for the long-lived Decay-Series parents, U and Th, are destined to be associated with the other members of the Decay-Series. The rocks that tend to host U and Th include some crystalline rocks such as granite and quartz-conglomerate metamorphics, and certain sedimentary rocks such as organic shales, sandstones carbonates and phosphorites. All materials at the earth`s surface eventually are broken down to their constituent parts and then, usually by the agency of water, transported to environments where they again may be geochemically sorted. The sorting processes at or near the surface ofmore » the earth operate on radioelements just as they do on other elements. The result is that the various radioelements are not simply dispersed but rather tend to accumulate in certain environments or rock types. Thus, the behavior of the radioelements found in the natural environment is based on their geochemistry, half-life, and the nature of their surroundings. 81 refs., 9 figs.« less
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The Distribution of Uranium and Thorium Decay-Series Radionuclides in the Environment—A Review
Journal of Environmental Quality, 1994Co-Authors: J. B. Cowart, W. C. BurnettAbstract:Natural radioactivity has played an indispensable role in the development of the earth to the form and shape that we now observe. Energy from radioactivity powers the large-scale processes that move the continents and cycle the elements. Most of the energy due to radioactivity comes from members of the three Decay-Series, two of which are parented by isotopes of uranium, {sup 238}U and {sup 235}U, and one by {sup 232}Th. These Decay-Series cascade to produce radioactive offspring such as Ra, Rn, and Po, but the ultimate fate of all members of these Series is to end as a stable isotope of Pb. Rocks or minerals that provide sites for the long-lived Decay-Series parents, U and Th, are destined to be associated with the other members of the Decay-Series. The rocks that tend to host U and Th include some crystalline rocks such as granite and quartz-conglomerate metamorphics, and certain sedimentary rocks such as organic shales, sandstones carbonates and phosphorites. All materials at the earth`s surface eventually are broken down to their constituent parts and then, usually by the agency of water, transported to environments where they again may be geochemically sorted. The sorting processes at or near the surface ofmore » the earth operate on radioelements just as they do on other elements. The result is that the various radioelements are not simply dispersed but rather tend to accumulate in certain environments or rock types. Thus, the behavior of the radioelements found in the natural environment is based on their geochemistry, half-life, and the nature of their surroundings. 81 refs., 9 figs.« less
