Progress achieved in EURAMET project 21GRD09 MetroPOEM: Metrology for the harmonisation of measurements of environmental pollutants in Europe

. The European Green Deal’s ambition for zero pollution requires development of highly sensitive techniques to detect ultra-low amounts of pollutants and isotope ratios, where mass spectrometry is a key method. The MetroPOEM project bridges the traceability gap between activity and mass-based measurements. Low level radioactive standard solutions ( 90 Sr, 237 Np, 234 U, 236 U, natural uranium (U nat ), 239 Pu, 240 Pu, 241 Am, 239,240 Pu) were distributed to 18 partner laboratories for measurement by mass spectrometric and decay counting techniques. The results and data analysis will be published separately. SI-traceable high precision methods were developed for isotope ratio determination of Li, B, Cr, Cd, Ni, Sb, Pb and U in seawater. Method development addressed analyte separation from the matrix, evaluation of calibration approaches, isotope fractionation corrections and uncertainty estimation. Seawater (250 L) was taken from the German North Sea exclusive economic zone (DE-EEZ) to develop two certified reference materials (CRMs). Part of this material was used to generate a CRM with SI traceability for isotope ratios of Li, B, Cr, Cd, Ni, Sb, Pb and U. The second part was used to generate a seawater CRM, spiked with U nat , 237 Np, 239,240 Pu and 241 Am. A solid silica-based CRM, spiked with U nat , 237 Np, 239,240 Pu and 241 Am, was produced by sol-gel synthesis, with ∼10 kg of inactive material for method development. These materials were characterised in accordance with ISO 17034 by interlaboratory studies between project partners, using techniques developed in the project. Two Good Practice Guides, on (i) measurement of radioactivity by mass spectrometry, and (ii) sample treatment, uncertainties, and mass bias quantification, are in draft.