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Radionuclide Transport Above a Near‐Surface Water Table: IV. Soil Migration and Crop Uptake of Chlorine‐36 and Technetium‐99, 1990 to 1993
Author(s) -
Shaw G.,
Wadey P.,
Bell J. N. B.
Publication year - 2004
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2004.2272
Subject(s) - radionuclide , soil water , lysimeter , crop , bioavailability , transfer factor , chemistry , environmental science , chlorine , environmental chemistry , agronomy , soil science , biology , bioinformatics , physics , organic chemistry , quantum mechanics , immunology
Vertical distributions of 36 Cl and 99 Tc are presented from deep and shallow lysimeters above artificially controlled water tables for a 4‐yr experiment from 1990 to 1993. Activity concentration profiles were all measured in late summer when a winter wheat ( Triticum aestivum L. cv. Pastiche) crop was harvested. After harvest, activity concentrations in different organs of the crop were determined and crop uptake quantified as both an inventory ratio (IR) and a transfer factor (TF w ), weighted to account for differential root and radionuclide distributions within the soil profile. Vertical distributions of radionuclides, crop roots within the soil, and IR and TF w values were each subjected to analysis of variance to estimate the individual and combined effects of soil depth and the year of the experiment on the results obtained. Chlorine‐36 and 99 Tc exhibited highly significant variations in activity concentrations with soil depth and from year to year, indicating considerable physical mobility of both radionuclides. Soil‐to‐plant transfer was also high for both radionuclides compared with data obtained for gamma‐emitting radionuclides. The IR values indicated that up to 40% of 36 Cl was incorporated in the crop's tissues at harvest, compared with a maximum of less than 1% for the less mobile gamma‐emitting radionuclides. On the basis of the TF w values determined, 36 Cl uptake by winter wheat exceeded 99 Tc uptake, indicating that 36 Cl is highly bioavailable. Factors controlling the migration and bioavailability of both 36 Cl and 99 Tc in soils are discussed.