Radium uptake by freshwater invertebrates

Questions regarding the mechanism and capacity for accumulation of 226Ra have only been addressed for one freshwater invertebrate, i.e. the freshwater mussel V. angasi. All of the results from studies conducted on V. angasi have confirmed the notion that calcium is the model for radium's metabolism by the mussel. The mussel takes up 226Ra and stores it in the granular deposits as an analogue of calcium. The mussel's ability to naturally accumulate 226Ra to high concentrations, i.e. to ∼ 3.4 Bq/g dry weight is due to a number of factors that are outlined below: (a) The mussel accumulates 226Ra in granules in a form (as a phosphate) that is relatively metabolically inert. (b) The mussel has the capacity to produce and store high densities of granules containing 226Ra within its tissue. (c) The store of granules per unit tissue tends to increase as the mussel increases in size and age. (d) Given this pattern of continual accumulation, the relatively long lifespan (∼ 25 a) of the mussel contributes to its ability to accumulate such high 226Ra concentrations. (e) Experimental studies demonstrated that it is the ratio of the water concentrations of 226Ra to calcium and, to a lesser extent magnesium, that determines the rate of accumulation of 226Ra by V. angasi. 38 refs, 11 figs, 2 tabs