用中子活化法研究鸡蛋中铱的含量与富铱饲料的关系

A study on the relationship between iridium concentration in hen eggs and the iriditum-enriched feedstuff by INAA

在鸡饲料中添加一定量的铱化合物（ＮＨ４）２ＩｒＣｌ６），喂养１４ｄ，用中子活化法分析所产蛋的铱含量．结果在蛋壳、蛋清、蛋黄中均发现了铱元素，其中蛋黄为最高。且它们的铱含量都随鸡饲养天数的增加呈上升趋势，到７、８ｄ后稳定在一定范围；当停止喂养含铱饲料后，铱含量迅速下降．另外，铱从食物到蛋壳的比率大约为万分之七．这一结果为铱有可能从食物链进入恐龙体内，并通过代谢作用沉积到蛋壳中的推断提供了科学依据。

Several hens were fed by adding ammonium chloroiridate into their forage. After two weeks, the Ir concentration in three fractions (eggshell, albumen, egg yolk) of their eggs were measured by INAA. Ir was found in all of the three parts. However, the highest concentration of Ir was found in the egg yolk fraction, which was about 10 times higher than that in the eggshell and albumen. Moreover, the longer the Ir-containing feedstuff was used, the higher the Ir concentration in the egg fractions was. After 7-8 days feeding, it kept stable. On the other hand, as soon as adding the Ir-containing additives were stopped, the Ir concentration in the egg fractions fell down quickly. The experimental results indicated that the ratio from the feedstuff to the eggshell via gastrointestinal pathway to be about 0.07 percent. The new result might be beneficial to explain the iridium-enriched dinosaur eggshell fossils and to interpret the origin of the mass extinct event of dinosaur occurred at the end of Cretaceous.