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.

Mercury speciation and mercury stable isotope composition in sediments from the Canadian Arctic Archipelago.

Total mercury (THg) and monomethylmercury (MMHg) concentrations as well as mercury (Hg) isotope ratios were determined in sediment cores sampled from six locations from the Canadian Arctic Archipelago (CAA). At most sites, THg concentrations showed a decreasing trend with depth, ranging from 5 to 61 ng/g, implicating possible increased Hg deposition and/or riverine inputs in top sediment layers. MMHg values showed large oscillations within the top 10 cm of the cores. This variability decreased at the bottom of the cores with MMHg concentrations ranging from less than12 to up to 1073 pg/g. Average concentrations of THg and MMHg in the top 10 cm were linearly correlated, whereas no correlation was observed with organic matter (loss on ignition). Mercury isotope ratios showed negative values for both δ202Hg (-1.59 to -0.55‰) and Δ199Hg (-0.62 to -0.01‰). δ202Hg values became more negative with depth, while the opposite was observed for Δ199Hg. The former is consistent with predicted historical atmospheric Hg trends as a result of increased coal burning worldwide. Hg isotope ratio measurements in CAA sediments offer additional opportunities to trace Hg processes and sources in the Arctic.