Soil–water distribution coefficients and plant transfer factors for 134Cs, 85Sr and 65Zn under field conditions in tropical Australia
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Date
2004
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Elsevier B. V.
Abstract
Measurements of soil-to-plant transfer of 134Cs, 85Sr and 65Zn from two tropical red earth soils (‘Blain’ and ‘Tippera’) to sorghum and mung crops have been undertaken in the north of Australia. The aim of the study was to identify factors that control bioaccumulation of these radionuclides in tropical regions, for which few previous data are available. Batch sorption experiments were conducted to determine the distribution coefficient (Kd) of the selected radionuclides at pH values similar to natural pH values, which ranged from about 5.5 to 6.7. In addition, Kd values were obtained at one pH unit above and below the soil–water equilibrium pH values to determine the effect of pH. The adsorption of Cs showed no pH dependence, but the Kd values for the Tippera soils (2300–4100 ml/g) exceeded those for the Blain soils (800–1200 ml/g) at equilibrium pH. This was related to the greater clay content of the Tippera soil. Both Sr and Zn were more strongly adsorbed at higher pH values, but the Kd values showed less dependence on the soil type. Strontium Kds were 30–60 ml/g whilst Zn ranged from 160 to 1630 ml/g for the two soils at equilibrium pH. With the possible exception of Sr, there was no evidence for downward movement of radionuclides through the soils during the course of the growing season. There was some evidence of surface movement of labelled soil particles. Soil-to-plant transfer factors varied slightly between the soils. The average results for sorghum were 0.1–0.3 g/g for Cs, 0.4–0.8 g/g for Sr and 18–26 g/g for Zn (dry weight) with the initial values relating to Blain and the following values to Tippera. Similar values were observed for the mung bean samples. The transfer factors for Cs and Sr were not substantially different from the typical values observed in temperate studies. However, Zn transfer factors for plants grown on both these tropical soils were greater than for soils in temperate climates (by more than an order of magnitude). This may be related to trace nutrient deficiency and/or the growth of fungal populations in these soils. The results indicate that transfer factors depend on climatic region together with soil type and chemistry and underline the value of specific bioaccumulation data for radionuclides in tropical soils. Crown Copyright © 2004 Published by Elsevier Ltd.
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Keywords
Cesium 134, Zinc isotopes, Strontium isotopes, Beta decay radioisotopes, Soils, Years living radioisotopes, Even-odd nuclei, Water, Plants, Biological accumulation, Australia
Citation
Twining, J. R., Payne, T. E., & Itakura, T. (2004). Soil–water distribution coefficients and plant transfer factors for 134Cs, 85Sr and 65Zn under field conditions in tropical Australia. Journal of Environmental Radioactivity, 71(1), 71-87. doi:10.1016/S0265-931X(03)00142-5