Uptake and Release of Cesium-137 by Five Plant Species as Influenced by Soil Amendments in Field Experiments
2003
Fuhrmann, Mark | Lasat, Mitch | Ebbs, Stephen | Cornish, Jay | Kochian, Leon
Phytoextraction field experiments were conducted on soil contaminated with 0.39 to 8.7 Bq/g of ¹³⁷Cs to determine the capacity of five plant species to accumulate ¹³⁷Cs and the effects of three soil treatments on uptake. The plants tested were redroot pigweed (Amaranthus retroflexus L. var. aureus); a mixture of redroot pigweed and spreading pigweed (A. graecizans L.); purple amaranth (A. cruteus L.) × Powell's amaranth (A. powellii S. Watson), referred to here as the amaranth hybrid; Indian mustard [Brassica juncea (L.) Czern.]; and cabbage (Brassica oleracea L. var. capitata). For control plants, the concentration ratios (CR) of ¹³⁷Cs were greatest for redroot pigweed and the amaranth hybrid, with average CR values of 1.0 ± 0.24 and 0.95 ± 0.14, respectively. The lowest value was for Indian mustard at 0.36 ± 0.10. The soil treatments included (i) application of NH₄NO₃ solution to the soil after plants had matured, (ii) addition of composted manure to increase organic matter content of the soil, (iii) combination of the manure and ammonium solution treatments, and (iv) controls. The ammonium solution gave little overall increase in accumulation of ¹³⁷Cs. The use of composted manure also had little influence, but the combination of the composted manure with application of ammonium solutions had a distinctly negative effect on plant uptake of ¹³⁷Cs. On average the fraction of ¹³⁷Cs taken up from the soil was reduced by 57.4 ± 1.2% compared with controls. This was the result of release of competing ions, primarily Ca, from the manure and was observed across all five plant species tested. The application of ammonium solution took place in the last two weeks before harvest. The reduction of plant ¹³⁷Cs content, by addition of the ammonium solution, as it interacted with the manure, indicates that substantial quantities ¹³⁷Cs can be released from the shoots of plants as a result of sudden changes in soil solution chemistry.
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