Pasture grass interception and retention of /sup 131/I, /sup 7/Be, and insoluble microspheres deposited in rain
During the summer of 1987, a series of field experiments was conducted for the National Cancer Institute to investigate the initial interception and postdeposition retention by pasture vegetation of soluble and insoluble forms of /sup 131/I in rain. These experiments employed mechanical rain simulators to reproduce rain intensities ranging from 1.4 to 12.2 cm/h and droplet sizes of 1.7 and 2.5 mm. The tracers used in this study were /sup 131/I as either iodide or periodate, /sup 7/Be/sup 2 +/, and three size classes of radioactively labelled polystyrene microspheres (3, 9, and 25 ..mu..m in diameter). These materials were applied in simulated rain, in amounts varying from 1 to 30 mm, to pure stands of white clover and fescue and to mixed stands of old field vegetation. For either chemical form of /sup 131/I, the fraction intercepted by vegetation over 5 cm tall decreased in almost direct proportion to the amount of rain. At low amounts of rain (1 to 2.5 mm) and high biomass (0.2 to 0. 3 kg/sub dry//m/sup 2/), the highest values of interception for /sup 131/I ranged from 20 to 55%. At high amounts of rain (20 to 30 mm) and low values of biomass (0.05 to 0.12 kg/sub dry//m/sup 2/), the interception fraction decreased to about 0.6 to 2%. Unlike the results for /sup 131/I, approximately 10 to 80% of the insoluble microspheres and soluble /sup 7/Be/sup 2 +/ was intercepted by vegetation over 5 cm tall, with only minor differences attributed to the amount or intensity of rain. The most important variable for the vegetation interception of these substances was the amount of standing biomass. The effect of differences in vegetation type was minor compared to the combined influence of biomass and the amount and intensity of rain. 26 refs., 37 figs., 20 tabs.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 6034285
- Report Number(s):
- ORNL-6542; ON: DE89014567
- Resource Relation:
- Other Information: Portions of this document are illegible in microfiche products. Environmental Sciences Division Publication No. 3247
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BERYLLIUM 7
DEPOSITION
IODINE 131
ABSORPTION
CONCENTRATION RATIO
CONTAMINATION
MICROSPHERES
PLANTS
RADIATION PROTECTION
RAIN
REMOVAL
ALKALINE EARTH ISOTOPES
ATMOSPHERIC PRECIPITATIONS
BERYLLIUM ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
EVEN-ODD NUCLEI
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPES
LIGHT NUCLEI
NUCLEI
ODD-EVEN NUCLEI
RADIOISOTOPES
500300* - Environment
Atmospheric- Radioactive Materials Monitoring & Transport- (-1989)