氚化水蒸气短期暴露后胡萝卜中氚的浓度

Tritium concentration in carrot plant after short-term exposure to HTO vapor

为了研究气态氚化水(HTO)事故释放后胡萝卜对HTO的吸收和有机结合氚(OBT)的形成,在4个不同的生长发育期把盆栽的胡萝卜暴露于氚化水蒸气1 h,并于试验结束和收获时分别测量胡萝卜地上部和地下部的组织自由水氚(TFWT)和有机结合氚(OBT)的含量。结果表明大部分情况下胡萝卜地上部分的TFWT浓度在一小时内就能与周围空气中HTO的浓度达到平衡。收获时地上部和地下部的相对TFWT浓度均低于试验结束时的值,收获时的值分别为试验结束时值的1/389~1/86和1/116~1/3,地下部减少的幅度小于地上部。试验在地上部和地下部的生长旺盛期进行,试验结束和收获时相应的这两部分OBT浓度也最高。收获时地上部和地下部OBT浓度小于试验结束时的值,但是肉质根膨大期时期进行试验,收获和试验结束时地上部和地下部相对OBT的浓度差异不大。收获时地下可食部分中OBT与TFWT的比值范围为2.79~20.73,在食入剂量评价中OBT的贡献要大于TFWT。

In order to study uptake and formation of tritiated water （HTO） and organically bound tritium （OBT） in carrots following acute exposure of airborne HTO, potted carrot plants were exposed to evaporated HTO for lh in an exposure box at four different growth stages. The concentrations of tissue free water tritium （TFWT） and OBT in top and root were measured at the end of exposure and at harvest, respectively. The results showed that in most cases, it usually takes shorter than 1 h for the TFWT concentrations in the whole carrot top to reach equilibrium with the HTO concentration in the ambient air moisture. The TFWT concentration in the carrot top and root at harvest were lower than those at the end of exposure. In the carrot top, the relative TFWT concentrations at harvest represented about 1/359-1/86 of those obtained at the end of exposure; while these values were found to be about 1/116-1/3 in the root. In the carrot top and root, the exposure at the vigorous growth period generally ended with a higher OBT concentration at the end of exposure and at harvest. The OBT concentrations in the carrot top and root at harvest were lower than those at the end of exposure. When the exposure was conducted at the fleshy root expending stage, no obvious difference was observed for the OBT concentrations in the carrot top and root between at harvest and at the end of exposure. The concentration ratios of OBT to TFWT at harvest ranged from 2.79 to 20.73 in root, it is estimated that OBT would contribute much more to the ingestion dose than TFWT does.