厦门港海区沉积物中^(226)Ra的测定

DETERMINATION OF ^(226)Ra IN THE MARINE SEDIMENTS IN THE XIAMEN HARBOUR

一、前言在用210Pb法测定湖泊或近海的现代沉积速率时,由226Ra的放射性强度来计算补偿的210Pb可获得更准确的沉积速率;此外,226Ra是极毒的长寿命亲骨性核素,对人体危害极大,故被列为环境监测的主要对象。鉴于上述原因,建立一种快速、灵敏、可靠的测定沉积物中226Ra的分析方法,具有重要意义。测定226Ra的方法主要有α放射法,射气法,和γ谱法等。由于沉积物中226Ra的含量很低,一般在10-12居里/克以下。因此在分析过程中,必须对沉积物中的226Ra进行分离和富集,同时选择一种既灵敏又准确的分析方法。本文提出了用阴离子交换分离,EDTA再纯化,硫酸钡镭制源,最后进行α计数的测定226Ra的方法。用该方法测定了厦门港海区三个站位沉积岩心中不同层次的226Ra含量,为该海区的环境评价提供了必要的数据。

A method for marine sediment 226Ra analys’s by anion-exchange separation,EDTA purification and(RaBa)SO4 source has been developed.It has a sensitivity of 3.0×10-14Ci/g(dried weight)for 5 g of sediment samples.The decontamination factors for some importer alpha radionuclei,such as U,Th and Po,approached 103 or greater.The chemical recovery of Ba was 73.5±3.6%and the radiochemidal recovery of 226Ra was 65.7±5.7%.The method has been applied to the determination of 226Ra in marine sediment samples from the Xiamen Harbour.The 226Ra content in cores from three stations was about 1.0 dpm/g(dried weight).