Gas-particle partitioning is one of the key factors that affect the environmental fate of semivolatile organic chemicals. Many organophosphate esters (OPEs) have been reported to primarily partition to particles in the atmosphere. However, because of the wide range of their physicochemical properties, it is unlikely that OPEs are mainly in the particle phase "as a class". We compared gas-particle partitioning predictions for 32 OPEs made by the commonly used OECD POV and LRTP Screening Tool ("the Tool") with the partitioning models of Junge-Pankow (J-P) and Harner-Bidleman (H-B), as well as recently measured data on OPE gas-particle partitioning. The results indicate that half of the tested OPEs partition into the gas phase. Partitioning into the gas phase seems to be determined by an octanol-air partition coefficient (log KOA) < 10 and a subcooled liquid vapor pressure (log PL) > -5 (PL in Pa), as well as the total suspended particle concentration (TSP) in the sampling area. The uncertainty of the physicochemical property data of the OPEs did not change this estimate. Furthermore, the predictions by the Tool, J-P- and H-B-models agreed with recently measured OPE gas-particle partitioning.

Air Quality Processes Research Section Environment and Climate Change Canada Egbert Ontario Canada L0L 1N0

Leuphana University Lüneburg Institute of Sustainable and Environmental Chemistry Scharnhorststraße 1 21335 Lüneburg Germany Helmholtz Zentrum Geesthacht Centre for Materials and Coastal Research Institute of Coastal Research Department for Environmental Chemistry Max Planck Strasse 1 21502 Geesthacht Germany

Leuphana University Lüneburg Institute of Sustainable and Environmental Chemistry Scharnhorststraße 1 21335 Lüneburg Germany Institute for Chemical and Bioengineering ETH Zürich 8093 Zürich Switzerland RECETOX Masaryk University 625 00 Brno Czech Republic

Leuphana University Lüneburg Institute of Sustainable and Environmental Chemistry Scharnhorststraße 1 21335 Lüneburg Germany University of Toronto Department of Earth Sciences 22 Russell Street Toronto Ontario Canada M5S 3B1 Centre for Environment Fisheries and Aquaculture Science Lowestoft Suffolk NR33 0HT United Kingdom

University of Toronto Department of Earth Sciences 22 Russell Street Toronto Ontario Canada M5S 3B1

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