Permanently charged and ionizable organic compounds (IOC) are a large and diverse group of compounds belonging to many contaminant classes, including pharmaceuticals, pesticides, industrial chemicals, and natural toxins. Sorption and mobility of IOCs are distinctively different from those of neutral compounds. Due to electrostatic interactions with natural sorbents, existing concepts for describing neutral organic contaminant sorption, and by extension mobility, are inadequate for IOC. Predictive models developed for neutral compounds are based on octanol-water partitioning of compounds (Kow) and organic-carbon content of soil/sediment, which is used to normalize sorption measurements (KOC). We revisit those concepts and their translation to IOC (Dow and DOC) and discuss compound and soil properties determining sorption of IOC under water saturated conditions. Highlighting possible complementary and/or alternative approaches to better assess IOC mobility, we discuss implications on their regulation and risk assessment. The development of better models for IOC mobility needs consistent and reliable sorption measurements at well-defined chemical conditions in natural porewater, better IOC-, as well as sorbent characterization. Such models should be complemented by monitoring data from the natural environment. The state of knowledge presented here may guide urgently needed future investigations in this field for researchers, engineers, and regulators.

College of Environmental Science and Engineering Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria Tianjin Key Laboratory of Environmental Remediation and Pollution Control Nankai University Tianjin 300350 P R China

Department of Analytical Chemistry Helmholtz Centre for Environmental Research UFZ Permoserstrasse 15 04318 Leipzig Germany

Department of Cell Toxicology Helmholtz Centre for Environmental Research UFZ Permoser Strasse 15 DE 04318 Leipzig Germany

Department of Environmental Geosciences Centre for Microbiology and Environmental Systems Science University of Vienna 1090 Wien Austria

Department of Environmental Sciences The Connecticut Agricultural Experiment Station New Haven; 123 Huntington St New Haven Connecticut 06504 1106 United States

Department of Soil and Water Sciences Institute of Environmental Sciences; Faculty of Agriculture Food and Environment The Hebrew University of Jerusalem P O Box 12 Rehovot 7610001 Israel

Environmental Analytics Agroscope 8046 Zürich Switzerland

Environmental Toxicology Center for Applied Geoscience Eberhard Karls University Tübingen Schnarrenbergstr 94 96 DE 72076 Tübingen Germany

Health and Environmental Risk Division National Institute for Environmental Studies Onogawa 16 2 305 8506 Tsukuba Ibaraki Japan

Institute for Analytical Chemistry University of Leipzig Linnéstrasse 3 04103 Leipzig Germany

Institute of Biogeochemistry and Pollutant Dynamics ETH Zürich 8092 Zürich Switzerland

Instrumental Analytical Chemistry and Centre for Water and Environmental Research University of Duisburg Essen Universitätsstrasse 5 45141 Essen Germany

Norwegian Geotechnical Institute P O Box 3930 Ullevaal Stadion N 0806 Oslo Norway

Norwegian University of Science and Technology NO 7491 Trondheim Norway

RECETOX Masaryk University 625 00 Brno Czech Republic

RWTH Aachen University Institute of Environmental Engineering Mies van der Rohe Straße 1 52074 Aachen Germany

Wageningen Environmental Research Wageningen University and Research P O Box 47 6700AA Wageningen Netherlands

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Environ Sci Technol. 2022 Aug 2;56(15):11093. doi: 10.1021/acs.est.2c05051. PubMed

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