Determination of environmental criteria for Polonium-210 in freshwater ecosystems
Tooshika H. Ramah (1), Richard R. Goulet (1,2)
(1) Department of Earth and Environmental Sciences, University of Ottawa
(2) CANMET-Mining, Natural Resources Canada, Ottawa
Tooshika H. Ramah (1), Richard R. Goulet (1,2)
(1) Department of Earth and Environmental Sciences, University of Ottawa
(2) CANMET-Mining, Natural Resources Canada, Ottawa
Polonium-210 released via effluent discharge from uranium, oil and gas and coal mining may have many ecological consequences on the freshwater environment. The residual uranium and other radioactive wastes in the form of tailings takes part in a decay chain generating radionuclides; 210Po is the decay product of 210Pb via 210Bi in the 238U series. With its limited solubility in water, Po-210 is an alpha emitter which tends to get adsorbed onto mineral surfaces and particulates dissolve and suspended in freshwater. Hence, it accumulates in bottom sediments. There is little information on transfer of polonium-210 along the food chain. In this paper, bioaccumulation data is collected along with concentrations in water and sediments and radioactive doses to freshwater organisms are computed in an attempt to determining a safe level of Po-210 in sediment and water for freshwater organisms. We hypothesize that the bioaccumulation of Polonium-210 by freshwater organism is linked to its concentrations in water and sediments. The activity concentration of Po-210 in freshwater, sediments and 41 freshwater organisms were therefore tabulated in a database, which were used to calculate the total dose rate using a tier 2 ERICA assessment. Bivalves had the highest total dose rate of 3.279 µGy h-1. Dose to pelagic fish, benthic fish, mollusks, gastropods, and crustaceans were graphically compared to Po-210 concentrations in water and in sediments with a safe dose rate set at 10 µGy h-1. A correlation analysis performed on GraphPad Prism showed that pelagic fish had a significant positive relationship with the total activity concentration of Po-210 in both water and sediment, while the others expressed a weak or no significant correlation which might be due to exposure via the food chain. The water criterion for Po-210 based on total dosage from pelagic fish was found to be 0.261 Bq L-1 and the sediment criterion 848.05 Bq kg-1. Although the current levels of Po-210 in freshwater bodies are relatively low compared to the environmental criteria obtained and do not seem to pose a significant radiological risk, its concentration should be closely monitored because of its enhanced bioaccumulation and its strong affinity towards certain internal tissues.