Comparison of radium-226 separation methods based on chromatographic and extraction resins for its determination by ICP-MS in drinking waters.

Over the past century, human activities have contributed to the release of 226 Ra (t½ = 1,600 y) in the environment, increasing the potential risks for human exposure and thus prompting scientists to monitor it. Inductively coupled plasma mass spectrometry (ICP-MS) is an alternative to alpha-spectrometry for the quantification of 226 Ra. However, the performances of radioanalytical procedures are rarely compared in a rigorous framework, which means that researchers may choose one on subjective factors or guesses. This article compares five published methods for the separation and preconcentration of 226 Ra in drinking waters based on chromatographic and extraction resins prior to its analysis by ICP-MS. We evaluated the turnaround time, generated wastes, and final cost of each protocol as the economic aspect can be an important criterion when selecting a method, particularly for sustainable environmental monitoring. Our results showed that 226 Ra was successfully separated and preconcentrated, yielding recoveries ranging between 84% and 105%. Method detection and quantification limits of respectively 2-7 fg L-1 (0.1-0.3 mBq L-1 ) and 6-24 fg L-1 (0.2-0.9 mBq L-1 ) were achieved when the separation method was coupled with ICP-MS. The turnaround times ranged between 6 and 21 hours, whereas the cost of the methods varied between 40 and 132 USD. This study highlights for the first time that methodologies recently published on the evaluation of 226 Ra levels in drinking water by ICP-MS have comparable figures of merit. Our results offer essential insights into the selection of the most suitable separation method.

Toxicity of tailing leachates from a niobium mine toward three aquatic organisms.

The aim of this research was to assess the ecotoxicity of leachates originating from a niobium mine located in Canada. These tailings contain considerable amounts of carbonates and phosphates and could potentially be used as fertilizer for agriculture. However, the presence of different contaminants linked with the ores mined, including rare earth elements and daughter elements of the uranium disintegration chain is of concern. Bioassays have been used to determine if the tailings leachates could be harmful. The assessment of the toxicity of progressive dilutions of five tailing leachates (808, 809, 810, 811 and 897) was performed on different organisms: phytoplankton Raphidocelis subcapitata and duckweed Lemna minor, based on their growth and chlorophyll a content, and water flea Daphnia magna based on their mobility, mortality and reproduction. Overall, the leachates showed higher toxicity to Raphidocelis subcapitata and Lemna minor, than toward Daphnia magna. Leachate 808 showed no toxicity to all organisms while leachate 810 showed significant effects to all species. The results can be explained by the leachate dissolved metal or nutrient concentrations, but also by the metal bioavailability which depends on pH and hardness. Generally, toxicity was observed in undiluted samples tested, which is not representative of the conditions that could occur in the environment. This supports the idea that these tailings could be used as fertilizer albeit more studies may be required, particularly to assess the toxicity of the tailings leachate for benthic organisms, the toxicity of the tailings for terrestrial organisms and the variations of soil and sediment physicochemical properties after tailing treatments.