Sorption of Polar and Ionogenic Organic Chemicals
The sorption process of polar chemicals to soil is in general similar to that of nonpolar chemicals and is in most cases still dominated by interactions with soil organic matter. In contrast, the sorption process for ionogenic organic chemicals (IOCs) is
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Contents 1 Sorption of Polar (Nonionic) Chemicals 1.1 Classical Linear Free Energy Relationships 1.2 Using a Systematic Polyparameter Approach to Account for all Nonionic Sorptive Interactions 2 Sorption of Ionogenic Chemicals 2.1 Relevance of Ionogenic Chemicals for Risk Assessment 2.2 Chemical Speciation for Ionogenic Chemicals 2.3 Sorbent Speciation Driving Surface Potentials 2.4 Relevant Solvent Parameters for Ionogenic Chemicals 2.5 Relevant Chemical Parameters for Ionogenic Chemicals 2.6 Relevant Sorbent Phases in Soils for Organic Cations 2.7 Sorption of Amphoteric IOCs References
Abstract The sorption process of polar chemicals to soil is in general similar to that of nonpolar chemicals and is in most cases still dominated by interactions with soil organic matter. In contrast, the sorption process for ionogenic organic chemicals (IOCs) is very different from that of nonpolar chemicals, particularly for IOCs where >90% is ionized as a cation, anion, or zwitterion. Organic ions in soil sorb to different parts of organic matter, by different processes, and often also to different soil components, such as minerals. This chapter provides a summary of several relatively recent studies that aimed to systematically uncover how the interactions between polar chemicals and ionic chemicals and soil components are influenced by (a) sorbate descriptors, (b) sorbent composition, and (c) aqueous phase conditions. The sorption data in several of these studies were collected on a single type of soil organic matter, micronized Pahokee peat, by a single method, dynamic highpressure flow-through column studies using controlled aqueous medium. This S. T. J. Droge (*) Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands e-mail: [email protected] Jose Julio Ortega-Calvo and John Robert Parsons (eds.), Bioavailability of Organic Chemicals in Soil and Sediment, Hdb Env Chem, DOI 10.1007/698_2020_517, © Springer Nature Switzerland AG 2020
S. T. J. Droge
chapter collected these consistent KOC values obtained for a structurally diverse range of (non)polar, cationic, (perfluorinated) anionic, and zwitterionic chemicals, which could serve as a (growing) reference database for environmental scientists, modelers, regulators, and registrants. Keywords Linear free energy relationships, Minerals, Organic matter, Polyparameter relationships, Sorption mechanisms
1 Sorption of Polar (Nonionic) Chemicals The sorption process of polar chemicals to soil is not too different from that of nonpolar chemicals. In most cases it is still dominated by the chemical’s hydrophobicity, the disruption of the cohesive energy of water, making it more favorable to be absorbed in the far less cohesive matrix of soil organic matter (SOM). Polar interactions such as hydrogen bonding typically weaken the sorption process, because they result in more favorable chemical interactions with water molecules relatively to SOM [1]. Whereas the octanol-water partitioning coefficient does include hydrogen bond interactions,
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