Beresford N A, Mayes R W, Barnett C L, MacEachern P J, Crout N M
Institute of Terrestrial Ecology, Merlewood Research Station, Grange-over-Sands, Cumbria, UK.
Radiat Environ Biophys. 1998 Dec;37(4):277-81. doi: 10.1007/s004110050129.
Considerable variability has been recorded in the radiocaesium activity concentration of muscle between individual sheep in the same flocks in upland areas that received fallout from the Chernobyl accident. In a previous paper we demonstrated that there is a propensity for certain sheep within a flock to be always amongst the most contaminated and others to be consistently the least contaminated. Here we report a study to determine the extent to which variation in the metabolism of radiocaesium by individual sheep may contribute to the observed variability within sheep flocks. The transfer coefficient and biological half-life of orally administered ionic radiocaesium in muscle were determined under controlled conditions in 22 ewes from an upland farm in an area of the UK which received comparatively high levels of Chernobyl fallout. There was considerable variation between individuals in both the transfer coefficient (0.19-0.56 day x kg(-1); mean 0.34 day x kg(-1)) and biological half-life in muscle (5.2-18.7 days; mean 9.8 days). Changes in liveweight during the study and feed intake together accounted for 72% of the variation in the derived transfer coefficients; liveweight change also accounted for 56% of the observed variation in biological half-life. In a subsequent study, the true absorption coefficient of radiocaesium was determined in 12 of the ewes. There was a positive correlation between transfer and true absorption coefficients (R = 0.57). We conclude that differences in the metabolism of radiocaesium will contribute to the observed variability in radiocaesium activity concentrations within sheep flocks in areas which were contaminated by Chernobyl fallout. We also suggest that for growing animals, the influence of liveweight change and feed intake on radiocaesium transfer may be greater than observed here. Similarly, in dairy cattle, for which feed intake changes considerably during the course of a lactation, large temporal variation in radiocaesium transfer to milk could be expected.
在切尔诺贝利事故沉降物影响的高地地区，同一羊群中个体绵羊肌肉的放射性铯活度浓度存在显著差异。在之前的一篇论文中，我们证明了羊群中的某些绵羊往往总是受污染最严重的，而其他一些则始终是受污染最轻的。在此，我们报告一项研究，以确定个体绵羊对放射性铯代谢的差异在多大程度上可能导致观察到的羊群内部差异。在英国一个受切尔诺贝利沉降物影响程度相对较高地区的山地农场，对22只母羊在受控条件下测定了口服离子放射性铯在肌肉中的转移系数和生物半衰期。个体之间的转移系数（0.19 - 0.56天×千克⁻¹；平均0.34天×千克⁻¹）和肌肉中的生物半衰期（5.2 - 18.7天；平均9.8天）均存在显著差异。研究期间体重变化和采食量共同解释了推导转移系数中72%的变异；体重变化也解释了观察到的生物半衰期变异的56%。在随后的一项研究中，测定了12只母羊放射性铯的真实吸收系数。转移系数和真实吸收系数之间存在正相关（R = 0.57）。我们得出结论，放射性铯代谢的差异将导致切尔诺贝利沉降物污染地区羊群中观察到的放射性铯活度浓度差异。我们还认为，对于生长中的动物，体重变化和采食量对放射性铯转移的影响可能比这里观察到的更大。同样，对于奶牛，在泌乳过程中采食量变化很大，预计放射性铯向牛奶中的转移会有很大的时间变化。
