“…We have also previously described sources of uncertainty and challenges for the harmonization of AAS and PAS SVOC air sampling, such as differences in sampler design, 11,24,25 including potentially problematic artifacts, 4,26 as well as differences in analytical performance between laboratories generating global SVOC air monitoring data. 27 This study focuses on the nal source of uncertainty for harmonization of AAS and PAS datathe determination of R Susing ten years (2009-2018) of continuous air monitoring data for PAHs, PCBs, OCPs, and PBDEs from the six sites in Europe with co-located EMEP AAS and MONET PAS to derive eld-based R S and compare them with results from the most commonly used models 22,23 for R S determination. This comparison enables us to address the challenge of reducing the uncertainties of PAS data 7 to improve the potential for harmonization of SVOC air monitoring data across Europe.…”