Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Chiba 263-8555, Japan.
J Environ Radioact. 2012 Feb;104:81-6. doi: 10.1016/j.jenvrad.2011.09.005. Epub 2011 Sep 29.
Effects of chronic γ-irradiation were investigated in the aquatic microcosm consisting of flagellate algae Euglena gracilis as producers, ciliate protozoa Tetrahymena thermophila as consumers and bacteria Escherichia coli as decomposers. At 1.1 Gy day(-1), no effects were observed. At 5.1 Gy day(-1), cell densities of E. coli showed a tendency to be lower than those of controls. At 9.7 and 24.7 Gy day(-1), population decrease was observed in E. coli. E. gracilis and T. thermophila died out after temporal population decrease and subsequent population increase in T. thermophila. It is likely that this temporal population increase was an indirect effect due to interspecies interactions. Effect dose rates of γ-rays were compared with effect concentrations of some metals using the radiochemoecological conceptual model and the effect index for microcosm. Comparison of these community-level effects data with environmental exposure data suggests that ionising radiation, gadolinium and dysprosium have low risks to affect aquatic microbial communities while manganese, nickel and copper have considerable risks. Effects of chronic irradiation were smaller than those of acute irradiation, and an acute to chronic ratio was calculated to be 28 by dividing an acute dose by chronic daily dose rate at which the effect index was 10%. This ratio would be useful for community-level extrapolation from acute to chronic radiation effects.
研究了由鞭毛藻类衣藻作为生产者、纤毛虫原生动物嗜热四膜虫作为消费者和细菌大肠杆菌作为分解者组成的水生微宇宙中慢性γ辐射的影响。在 1.1 Gy·day-1 时，没有观察到影响。在 5.1 Gy·day-1 时，大肠杆菌的细胞密度有低于对照的趋势。在 9.7 和 24.7 Gy·day-1 时，大肠杆菌的种群减少。衣藻和嗜热四膜虫在经历了暂时的种群减少和随后的嗜热四膜虫种群增加后死亡。这种暂时的种群增加很可能是由于种间相互作用的间接影响。利用放射化学生态学概念模型和微宇宙效应指数，将 γ 射线的效应剂量率与一些金属的效应浓度进行了比较。将这些群落水平效应数据与环境暴露数据进行比较表明，电离辐射、钆和镝对水生微生物群落的影响风险较低，而锰、镍和铜的影响风险较大。慢性照射的影响小于急性照射的影响，通过将急性剂量除以效应指数为 10%的慢性日剂量率，计算出急性到慢性的比值为 28。该比值可用于从急性到慢性辐射效应的群落水平外推。
