Uptake and Loss of Radioactive Ruthenium by Freshwater Organisms

Abstract

The uptake of radioactive ruthenium by freshwater organisms in a biocenose was studied in an aquarium ecosystem which consisted of natural river water, duckweeds, mud snails, river snails, freshwater mussels, crucian carps and bottom sands. The aquarium was equipped with a filtration-aeratian apparatus.
After a single addition of ¹⁰⁶Ru in nitrosyl ruthenium nitrato complex forms into the aquarium ecosystem, the uptake and distribution of ¹⁰⁶Ru in organisms were observed.
The loss of ¹⁰⁶Ru from organisms were also studied.
The radioactive concentration in rearing water rapidly decreased in 1 or 2 days and then maintained a constant level. The radioactive concentrations of ¹⁰⁶Ru in organisms reached peaks in 1 or 2 days, then gradually decreased with a gradual tendency to reach an equilibrium state. The deposition of ¹⁰⁶Ru in upper layer of bottom sands reached an equilibrium state in about 7 days.
The average concentration factors for ¹⁰⁶Ru in organisms showed a decreasing tendency in following order: duckweeds, mud snails, river snails, freshwater mussels and crucian carps.
In soft tissues of mud snails, freshwater mussels and river snails, the concentration factors for ¹⁰⁶Ru (RuNO-nitrato) were less than about several times in rearing single species.
However, in crucian carps no significant difference of the concentration factor for ¹⁰⁶Ru was observed with different rearing conditions.
In crucian carps, about 80% of total radioactivity was distributed in visceral mass including digestive tract.
The loss of ¹⁰⁶Ru in chlorocomplex forms from some organisms was more rapid than that of ruthenium in nitrosyl nitrato complex forms. Two biological half-lives of ¹⁰⁶Ru were observed in some tissues.