^(60)Co在海水中化学种态及其在海洋生物体中浓集和排泄的研究

STUDY ON THE CHEMICAL SPECIES OF ^(60)Co IN SEAWATER AND ITS CONCENTRATION AND EXCRETION IN OCEANIC ORGANISMS

用超滤法研究了 pH =7.31的条件下60 Co在海水与不同粒度胶体间的分布 ,结果表明 ,大约86%的60 Co是以非胶体的形式存在。用阳离子交换法在离子强度为 0 .67的条件下测定了Cl- 、SO4 2 - 和CO32 - 与Co(Ⅱ )的一级配合物稳定常数 β1,它们分别为 0 .4 47、5 .5 6和 1 .31× 1 0 3。假设Co(Ⅱ )的化学平衡仅由海水中主要的无机阴离子决定 ,利用实验获得的配合物稳定常数 ,计算了 pH =8.0的海水中Co(Ⅱ )的各种化学种态所占的百分比 ,结果为 :Co2 + ( 70 %) ,CoCl+ ( 1 7%) ,CoSO4 ( 1 1 %) ,CoCO3( 1 %) ,CoOH+ ( 1 %)。并在此基础上研究了扇贝和贻贝对60 Co的吸收与排泄的生态参数和60 Co的两种化学种态比例的可能影响。结果表明 ,未发现不同化学种态比例会引起生态参数的显著改变 ;但是 ,不同化学种态比例可能会影响60 Co在海洋生物体内的分布。此外 ,实验结果表明 ,扇贝对60 Co的浓集因子比贻贝高 ,扇贝的生物半排期 (Tb1/ 2 )和吸收达到 90 %饱和度时所需时间 (SSt)也比贻贝长。

The distribution of 60Co on colloidal particles with different sizes in seawater were studied with ultrafiltration. It has been shown that about 86% of Co(Ⅱ) is in soluble form, the apparent stability constants for chloride, sulfate and carbonate anions with Co(II)at ionic strength of 0.67 were determined by the cation exchange method. Their β 1 values were 0.448, 5.56 and 1.31×103, respectively. It is estimated the chemical species of Co(II) in seawater at the pH of 8.0 presents as Co 2+(70%),CoCl+(17%),CoSO 4(11%),CoCO 3 (1%) and CoOH+(1%), assuming that only major inorganic anions are responsible for the chemical equilibrium of Co(Ⅱ). The concentration and excretion of oceanic organisms such as scallop, mussel and seaweed through seawater pathway were also investigated. The results show that the 60Co concentration factor(CF) in scallop was higher than mussel, the biological half-life and the time to get the intake maximum for scallop also longer than mussel. It has not been found that ecological parameters of oceanic organisms were changed significantly with the ratio of different chemical species. But it seems that the distribution of 60Co in scallop and mussel may be affected. (