Linking micro-aggregation to the sequestration of organic pollutants in soils

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Physicochemical and steric properties of organic chemicals on the one hand and physicochemical surface properties and structural properties of the sorbent on the other hand determine sorptive interactions at biogeochemical interfaces. In order to gain a mechanistic understanding of these interactions we want to combine macroscopic, micro-calorimetric, and spectroscopic methods. We hypothesise that sorption and distribution of a polar organic chemical at biogeochemical interfaces is either determined by the molecules hydrophobic R-groups (R-determined) or its functional groups (F-determined). To test our hypothesis we will study sorption of bisphenol A and fenhexamid (R-determined chemicals), and bentazon and naproxen (F-determined chemicals) in pure systems of minerals (kaolinite, illite, gibbsite, and quartz), in model substances for biofilms (polygalacturonic acid and dextran), in combined systems of mineral phases with organic layers, and in topsoils and subsoils. Interpretation and modelling of sorption isotherms and sorption kinetics derived from batch experiments together with results from diffusion experiments with polysugars of variable crosslinking will provide macroscopic insight into sorptive interactions. Information regarding the thermodynamics of sorption will by derived from micro-calorimetry. Spectroscopic (ATR FTIR, NMR) measurements deliver information on molecular interactions and structure.