Soils radionuclide concentrations

For comparison, we have calculated the health effects for typical residential properties (4 occupants each) based on 1) the naturally occurring background radiation levels and radionuclide concentrations in four cities across the U.S. (see Table V) and 2) the EPA (CFR, 1981) guideline values (20 yR/h, 0.02 WL, 5 pCi Ra-226/g of soil) for cleanup at inactive uranium processing sites (see Table VI). 

The beginning radionuclide concentration values for individual plates are initial conditions determined by the soil concentration profiles. Thus, a continuous tabulation of the concentration profiles is maintained during simulation. This is of primary importance during rain periods when no overland flow occurs since it will tend to alter the surface soil concentration. Decreases in the surface layer radioaerosol concentration arising from infiltration will cause a corresponding decrease in subsequent surface runoff aerosol transport. 

There is a disadvantage with the use of environmental samples to assess the radionuclide concentrations in the environment. This arises since there is the potential for contamination of such samples from previously deposited material. This material may or may not originate from the source of interest and there may be significant contributions from Chernobyl and weapons fallout. Such contamination pathways include soil splash, the deposition of resuspended material and root uptake. 

DOE. 1995. Radionuclide concentrations in terrestrial vegetation and soil on and around the Hanford site, 1983 through 1993. Richland, WA U.S. Department of Energy. DE-AC06-76RL01830. 

Heavy metal and radionuclide concentrations in soils increase due to man-made pollution. One of the first entry points of such elements into plant ecosystems is the rhizosphere, defined as the soil under the biological, physical and chemical influence of roots. Arbuscular mycorrhizal (AM) fungi, symbiotic microorganisms associated with the roots of many plant species, provide a direct link between soil and roots and affect metal transfer to plants. The present chapter includes recent laboratory work and some research aspects stiU to be adressed on the contribution of AM fungi to plant metal uptake. The necessity to develop new and adapted approaches, such as compartment devices and root-organ cultures, to separate AM to root contribution to metal uptake is emphasized. Available data may be difficult to compare because they were obtained under different experimental conditions. However, they suggest that the transfer of heavy metals from AM fungi to plants may be metal specific. Further research should focus on the mechanisms involved in reduced or improved uptake of metals by mycorrhizal plants, on AM tolerance to metals and radionuclides and on AM functional diversity in polluted soils. AM contribution to metal uptake should also be quantified to include data in models of plant uptake. 

Heavy metal and radionuclide concentrations in soils increase owing to man-made pollution related to industrial, agricultural or urban activities. Such concentrations can reach toxic levels and create major environmental and health problems. One of the first entry points of metals into plant ecosystems is the rhizosphere, defined as the soil under the biological, physical and chemical influence of roots. In the rhizosphere, the plant releases root exudates that soil microorganisms feed on, and... 

Radionuclides in groundwater are identified and quantified to determine sources of discharges or leaks into the ground. They can indicate the presence of radionuclides in subsurface soil, and predict radionuclide concentrations in surface water reached by groundwater. Groundwater usually is collected from wells that have been drilled... 

Another concern relates to samples in which the radionuclide is not uniformly distributed, such as biological tissue, vegetation, or soil. The measured radionuclide concentration may represent either the entire sample or a defined fraction, e.g., the soluble portion, a specified particle size range, vegetation without soil (and vice versa), or a dissected animal organ or tissue. Any separation of the defined fraction should be performed as early as possible in the process, possibly at collection. The separation process often is imperfect, either because of losing some of the radionuclide to other fractions or retaining some of the other fractions. Serious error is introduced when the radionuclide concentration in the extraneous fractions far exceeds its concentration in the fraction of interest. 

Specific treatment combinations can be designed to match airborne contaminants from the physical or chemical operations, the type of sample (solid, liquid, gas), and the quantity that is processed. For example, sample preparation rooms where soil and vegetation are dried, ashed, ground and sieved require particle filter combinations but not charcoal beds and scrubbers. For treating laboratory air, the multiple stage filter system should be based on the expected maximum radionuclide concentration and airborne fraction of the processed samples. Typical combinations include pre-filters, HEPA filters and charcoal beds. 

The set of regularly obtained data on radionuclide concentrations in air can be directly used to assess the annual intake and the associated committed dose. If measurement data are unavailable or insufficient, radionuclide concentrations in air can be roughly estimated from soil deposition rates by using a resuspension model. 

The net effect of passage through arthropod food chains was a significant rearrangement of relative abundances of the three radionuclides. Concentrations (pCi/mg) of Cs, Ru and o in soils were of the order of approximately 14 28 5. At the predator trophic level these had been rearranged to approximately 0.1 2.1 0.1. All three radionuclides... 

Select Radionuclide Concentrations Detected in Soil Samples Adjacent to the 116-N-l Facility and in the 116-N-l Trench Sediment Samples (pCi/g). T5-25... 

Average Radionuclide Concentrations (pCi/g) Detected in Soil Samples near the 116-N-l Crib and Trench from... 

Data from these loos indicate that verv low concentrations of radionuclides such as Xo, Xs, "Sb, and Ru were present in Well 199-N-9 soils above the water table, although the concentration increases markedly in soils at the water table. Wells 199-N-12 and 199-N-13 are more distant from the trench and had lower radionuclide concentrations in the unsaturated zone but also had elevated concentrations at the water table (within the saturated zone). These data indicate that extensive lateral migration of contaminants from the trench within the unsaturated zone is not apparent in these borings (DOE-RL 1990). Mechanisms that control the lateral migration of contaminants through the unsaturated zone include dispersion, diffusion, capillary flow, migration through a low-permeability zone because of increased moisture content and perched water, and the adsorption capacity of the soil. 

Table 5-15. 1980 Select Radionuclide Concentrations Detected in Soil...

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