氚化水(HTO)气态释放后在大豆中的积累和转化研究

为了研究气态氚化水(Tritiated water,HTO)事故释放情况下其在植物中的迁移转化情况,选取盆栽大豆作为研究对象,分别在苗期、花荚期、灌浆期和成熟期模拟气态氚化水短期释放1 h,分不同时期采集样品测量大豆叶片和籽粒中的组织自由水氚(Tissue free water tritium,TFWT)和有机氚(Organically bound tritium,OBT)浓度,研究了TFWT和OBT的变化情况.结果表明,如果暴露试验在苗期和成熟期进行,叶片中的TFWT与周围空气中氚化水达到平衡的时间大于1 h,而花荚期和灌浆期则小于1 h.总的来说,随着时间的推移,大豆叶片和籽粒中的TFWT和OBT均呈现降低的趋势,与暴露试验结束后相比,差异达极显著水平.4个不同生育期进行暴露试验,收获时叶片中TFWT浓度分别为暴露试验结束时的 0.122%、0.0234%、0.0948%和75.87%,OBT的浓度分别为暴露试验结束时的 2.47%、4.32%、3.67%和31.68%;花荚期、灌浆期和成熟期进行暴露试验收获时籽粒中TFWT的浓度与暴露试验结束时TFWT的浓度相差倍数分别为6486、7902和4,OBT的浓度分别为暴露试验结束时的31.48%、32.03%和116.73%.4个不同生育期进行暴露试验,收获时大豆籽粒中的OBT与TFWT的浓度比率分别为5、9、34和0.4,说明摄入剂量中OBT的贡献大于TFWT,但气态氚化水在大豆成熟期释放,TFWT在摄入剂量的贡献中要大于OBT.因此,在植物氚浓度预测模型中,应根据气态氚化水事故释放时植物所处的不同生育期确定相应的参数,这样才能更为准确和客观的评价氚的摄入剂量.

Study of accumulation and transformation of HTO in soybean for atmospheric releases of tritiated water

In order to study the transfer and transformation of released accidentally tritiated water (HTO) in plant, the potted soybean plants from seedling to mature stages were exposed to HTO vapor for 1 h. The concentrations of tissue-free water tritium (TFWT) and organically bound tritium (OBT) in leaf and grain collected at different stages were measured. It was indicated that the leaf TFWT concentration reached equilibrium with the atmospheric HTO over 1 h at seedling and mature stage, but less than 1 h at flowering and filling periods. The TFWT and OBT concentration in the leaves and grain decreased after the exposure experiment of HTO vapor at different growth stages, with significant differences from those at the end of exposure. During the period between the exposure and harvest, the TFWT concentrations in leaves were 0.122%, 0.0234%, 0.0948% and 75.87% of that at the end of exposure, respectively, and the leaf OBT concentrations at harvest were 2.47%, 4.32%, 3.67% and 31.68% of that at the end of exposure, respectively. At the harvest, the reduction factor of the TFWT concentration in the grain were 6486, 7902 and 4 and the OBT concentration in the grain were 31.48%, 32.03% and 116.73% of that at the end of exposure for different exposure experiments conducted at podding, filling and mature period. The ratios of OBT concentrations to TFWT concentrations in the grain at harvest were 5,9,34 and 0.4 for different exposure times, and it showed that OBT contributed much more to the ingestion dose than TFWT. However, lower OBT contributions could be estimated for an exposure occurring in the mature stages. Therefore, the parameters of tritium concentration prediction model in plant should be determined based on the different growth stages for accidental release of atmospheric HTO so that the ingestion doses for tritium could be estimated accurately and objectively.