Inter-cultivar variation in soil-to-plant transfer of radiocaesium and radiostrontium in Brassica oleracea.

Radiocaesium and radiostrontium enter the human food chain primarily via soil-plant transfer. However, uptake of these radionuclides can differ significantly within species (between cultivars). The aim of this study was to assess inter-cultivar variation in soil-to-plant transfer of radiocaesium and radiostrontium in a leafy crop species, Brassica oleracea. This study comprised four independent experiments: two pot experiments in a controlled environment artificially contaminated with radiocaesium, and two field experiments in an area contaminated with radiocaesium and radiostrontium in the Chernobyl Exclusion Zone. Radiocaesium concentration ratios varied 35-fold among 27 cultivars grown in pots in a controlled environment. These 27 cultivars were then grown with a further 44 and 43 other cultivars in the Chernobyl Exclusion Zone in 2003 and 2004, respectively. In the field-grown cultivars radiocaesium concentration ratios varied by up to 35-fold and radiostrontium concentration ratios varied by up to 23-fold. In three of these experiments (one pot experiment, two field experiments) one out of the 27 cultivars was found to have a consistently lower radiocaesium concentration ratio than the other cultivars. The two field experiments showed that, five out of the 66 cultivars common to both experiments had consistently lower radiocaesium concentration ratios, and two cultivars had consistently lower radiostrontium concentration ratios. One cultivar had consistently lower radiocaesium and radiostrontium concentration ratios. The identification of cultivars that have consistently lower radiocaesium and/or radiostrontium concentration ratios suggests that cultivar selection or substitution may be an effective remediation strategy in radiologically contaminated areas. Future research should focus on plant species that are known to be the largest contributors to human dose.

Inter-varietal variation in caesium and strontium uptake by plants: a meta-analysis.

Radiocaesium and radiostrontium enter the foodchain primarily via plant root uptake. Selecting varieties of crop that display low accumulation of these radionuclides has been suggested as an economically and socially acceptable remediation strategy for radiologically contaminated land. However, there is insufficient information available to assess the feasibility of this remediation approach. This paper presents a comprehensive literature-based evaluation of inter-varietal variation in accumulation of Cs and Sr in crop plants. Thirty-seven publications studying 27 plant species were identified as appropriate for these analyses. Inter-varietal variation was expressed at the ratio of the maximum to minimum observed concentrations for a given crop species and element and ranged from 1.0 to 6.3 and from 1.0 to 4.5 for Cs and Sr respectively. This variation suggests that exploitation of inter-varietal variation could be used in some crop species to reduce the transfer of these radionuclides to a similar extent to existing remediation strategies. Low-Sr accumulating varieties were also found to have lower concentrations of Ca, whereas low Cs-accumulating varieties were not shown to have low K accumulation. Concentrations of Cs and Sr in plants were not related, suggesting that finding varieties displaying low accumulation of both Sr and Cs may not be feasible. Varietal selection could be an effective remediation strategy, and could be used in combination with other existing methods, such as fertilisation and ploughing. However, a thorough investigation of species contributing the most to ingestion doses is recommended to fully determine the feasibility of varietal selection as a remediation strategy. The reproducibility of inter-varietal variation between sites and growing seasons should be the focus of future research.