Radium in soil

Radium in soils and sediment does not biodegrade nor participate in any chemical reactions that transform it into other forms. The only degradation mechanism operative in air, water, and soil is radioactive decay. Radium has 16 known isotopes (see Chapter 3), but only 4 occur naturally (Radium-223, -224, -226, and -228). The half-life of radium-226 is 1,620 years. The half-lives of radium- 228, radium-223, and radium-224 are 5.77 years, 11.4 days, and 3.64 days, respectively. 

Radon is a radioactive gas produced when radium in soil and rock decays. It is a known carcinogen. The data above show radon levels measured in a community in Australia. Select a method for graphing these data. Explain the reasons for your choice, and graph the data. 

For regional reconnaissance uranium is its own best indicator, being readily oxidized to the hexavalent state and then remaining very mobile under oxidizing conditions. For detailed prospecting uranium and its decay products are interesting for assay purposes. The low mobility of radon and radium from their source makes them good tracers. To date, experience in France shows the results for radon always to have been better in water and for radium in soils. 

Greeman, D.J., A.W. Rose, J.W. Washington, R.R. Dobos, and E.J. Ciolkosz. 1999. Geochemistry of radium in soils of the eastern United States. Appl. Geochem. 14 365-385. 

Rona E, Urry WD (1952) Radium and uraninm content of ocean and river waters. Am J Sci 250 241-262 Rosholt J, Doe B, Tatsnmoto M (1966) Evolntion of the isotopic composition of nraninm and thorinm in soil profiles. Geol Soc Am Bull 77 987-1004... 

Radon is a naturally occurring, chemically inert, radioactive gas. It is colorless, odorless, and tasteless. It is part of the uranium-238 decay series, the direct decay product of radium-226. Radon moves to the earth s surface through tiny openings and cracks in soil and rocks. High concentrations of radon can be found in soils derived from uranium-bearing rocks, such as pitchblende and some... 

Figure 1. Schematic illustration of factors influencing the production and migration of radon in soils and into buildings. Geochemical processes affect the radium concentration in the soil. The emanating fraction is principally dependent upon soil moisture (1 0) and the size distribution of the soil grains (d). Diffusion of radon through the soil is affected primarily by soil porosity ( ) and moisture content, while convective flow of radon-bearing soil gas depends mainly upon the air permeability (k) of the soil and the pressure gradient (VP) established by the building.

Factors influencing the production and migration of radon in soils have been examined, and various sources of geographic data have been discussed. Two significant soil characteristics include air permeability and, less importantly, radium concentration. While there are, at present, few opportunities to compare the larger-scale data with on-site field measurements, those comparisons that have been made for both surface radium concentrations and air permeability of soils show a reasonable correspondence. Further comparisons between the aerial radiometric data and surface measurements are needed. Additional work and experience with SCS information on soils will improve the confidence in the permeability estimates, as will comparisons between the estimated permeabilities and actual air permeability measurements performed in the field. 

The subsoil is the principal source of radon in this house. Both the activity concentration of radium-226 in subsoil and of radon in soil gas are above levels for building ground that might result in significant indoor radon concentrations. The radon decay-product concentration in the dwelling before remedial measures were taken was substantially higher than the reference value of 120 mWL. 

Radon in indoor air arises primarily from radium in the soil. The radon in the soil gas flows under a pressure gradient from the soil into the building. In some cases building practices can lead to high radon levels in the living areas of the house. Radon is chemically quite inert and does not pose a significant radiation health hazard in itself because the retained fraction in the body is so low (Mays et al., 1958). It is, however, an excellent vehicle for the dispersion of its short-lived radioactive decay products. 

The initial exploration and subsequent drilling in the Windsor area was sparked by the discovery of radon anomalies in the soil gas and well waters in the area (Quarch et al. 1981 Fig. 2). In addition, uranium and radium in well waters were weakly anomalous in the area. It is therefore not difficult to infer that these geochemical techniques are useful exploration tools for deposits of this type and that there are environmental Issues related to uranium occurrences in the Horton Group. 

Linsalata P, Penna Franca E, Sachett I, et al. 1987. Radium, thorium, and the light rare earth elements in soils and vegetables grown in an area of high natural radioactivity. DOE Symp Ser 59 131-146. 

Sill et al. [26] have described a procedure by which virtually all alpha-emitting nuclides of radium through californium can be determined in soil, singly or in any combination in a single sample. 

Radium is a naturally-occurring silvery white radioactive metal that can exist in several forms called isotopes. It is formed when uranium and thorium (two other natural radioactive substances) decay (break down) in the environment. Radium has been found at very low levels in soil, water, rocks, coal, plants, and food. For example, a typical amount might be one picogram of radium per gram of soil or rock. This would be about one part of radium in one trillion (1,000,000,000,000) parts of soil or rock. These levels are not expected to change with time. 

Radium is a naturally-occurring metal that is almost ubiquitous in soils, water, geologic materials, plants, and foods at low concentrations. The utilization of radium, uranium, and fossil fuels has resulted in the redistribution of radium in the environment by way of air, water, and land releases. 

The radium-228 content of fly ash has varied from 1.8 to 3.1 pCi/g (0.07 to 0.12 Bq/g) (Eisenbud and Petrow 1964). If it is assumed that the total radium content of fly ash is 5 pCi/g (0.19 Bq/g), and that 1% of the ash generated at all coal-fired power plants in the United States escapes into the atmosphere, then an order-of-magnitude estimate of the amount of radium released each year would be 2.2 Ci (81,000,000 kBq) (Roy et al. 1981). Eisenbud and Petrow (1964) estimated that a single 1000-megawatt coal-fired power plant will discharge about 28 mCi (1,037,000 kBq) of total radium per year. Radium-226 has been detected in soils in industrial regions at levels up to 8.1 pCi/g (0.30 Bq/g) (Jaworowski and Gryzbowska 1977). 

Radium in water may be readily adsorbed by sediments, soils, and aquifer components. It has been experimentally demonstrated that radium can be adsorbed by soils and sediments (Benes and Strejc 1986 Landa and Reid 1982), ferric hydroxide and quartz (Benes et al. 1984 Valentine et al. 1987), kaolinite and montmorillonite (Benes et al. 1985), and muscovite and albite (Benes et al. 1986). 

Transfer from plants to cattle. There is a potential for human exposure to radium by the consumption of beef and milk derived from cattle who graze on forage grown in soils containing radium. The mean ratio of radium-226 in milk to that in the animal s diet has been estimated to be 3.8 x 10 (Watson et al. 1984). A similar ratio or transfer coefficient for flesh was 6.8 x 10 . 

Radium is a naturally-occurring metal and is almost ubiquitous at low concentrations in air, water, soil, rocks, and food. The median concentrations of radium-226 and radium-228 in drinking water are generally low, but there are geographic areas where higher concentrations of radium are known to occur. The utilization of coal and uranium has resulted in re-distributing radium in the environment, but the overall effects appear to be small. Estimated levels of average human exposure to radium of nonoccupational populations are presented in Table 5-1. 

The concentrations of radium-226 in soils that were contaminated by mining or milling activities have ranged from less than 1 to 3,700 pCi/g (0.037 to 137 Bq/g) (Kalin 1988 Landa 1984 Tracy et al. 

No information was located on the occurrence of the other radium isotopes in soil or rocks. 

Bioavailability from Environmental Media. Data on the absorption of radium from environmental media via inhalation, oral, and dermal exposure would be useful in determining potential risks for organisms (humans, animals and plants) that have been exposed to radium in air, soil, or natural waters. 

Food Chain Bioaccumulation. The existing information indicates that radium may be transferred through the food chain from lower trophic levels to humans. Additional monitoring studies in areas where radium occurs naturally at high concentrations in soil would be helpful to determine if this pathway is a significant route of exposure. The transfer of radium-228 from soils through the food chain has not been assessed. 

If ps (kg m-3) is the bulk soil density, AR (Bq kg-1) the specific activity of radium in the soil, a the emanating coefficient, and A (s-1) the decay constant of radon, then PsARa atoms, or psARaX Bq of radon, enter the interstitial air per m3 of soil volume per second. At depth in the soil, the rates of entry and radioactive decay of radon are equal, so its activity in interstitial air is... 

RANDON A naturally occurring radioactive inert gas formed by radioactive decay of radium atoms in soil and rocks and that cannot be seen, smelled, or tasted. 

Radon A naturally occurring radioactive inert gas that cannot be seen, smelled, or tasted, formed by radioactive decay of radium atoms in soil and rocks RDA Recommended daily allowance the National Academy of Sciences sets the required nutrient values for healthy people in the United States. The values take into consideration the needs of all individuals RDI Recommended daily intake... 

Unauthorized landfill disposal of uranium processing wastes (e.g., Shpack Landfill in Norton, Massachusetts, and the Middlesex Municipal Landfill in Middlesex, New Jersey) has resulted in soil contamination (Bechtel National 1984 Cottrell et al. 1981). Also, elevated uranium concentrations have been measured in soil samples collected at 30 of 51 hazardous waste sites and in sediment samples at 16 of 51 hazardous waste sites (HazDat 1998). The HazDat data includes both Superfund and NPL sites. Elevated concentrations of uranium have been detected in soil, in surface water, in groundwater, or in all three of these environmental media from these sites. In several cases, the uranium concentrations in soils were significantly elevated. For example, uranium concentrations from the Shpack/ALI site were found to be 16,460 pCi/g (24,000 pg/g). At the United States Radium Corporation site (New Jersey), uranium concentrahons ranged from 90 to 12,000 pCi/g (130-18,000 pg/g) for the Monticello site (Utah), uranium levels were reported to range from 1 to 24,000 pCi/g (1.5-36,000 pg/g) (HazDat 1998). 

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