This project proposal will answer the following questions:
Objective: How can the aqueous phase biodegradation kinetics of poorly water soluble substances be measured without the influence of bioavailability factors, i.e., without (de)sorption effects?
Objective: How can the desorption rates of poorly water soluble substances from soils, sediments and STPs be reliably assessed over time?
Objective: How can both biodegradation and (de)sorption be unified in one model, and can the model be used to differentiate (de)sorption and biodegradation in standard tests?
Chemicals with an extremely low aqueous solubility in the range of a few µg/L are used in a broad range of applications. Organic compounds with low aqueous solubility are also hydrophobic. Currently, more than 850 substances with a log KOW ≥ 5.5 are registered in the European Chemicals Agency (ECHA) database under the EU Chemical Legislation regulation (REACh; data merging: ECHA 2015, OECD 2015). In the field of cosmetics, often referred to as Personal Care Products (PCP), 2 – 5 % of the total annual production in Germany is estimated to consist of highly hydrophobic compounds and are, for example, used as emulsifiers (Tolls et al. 2009). Besides the high production volumes, the typical way of application, i.e., ‘rinse off’ application, promotes the potential release of substantial amounts of these chemicals into wastewater and the aquatic environment (Brooks et al. 2009, Daughton 2002). Therefore, reliable assessments of the environmental fate and potential toxicity are urgently needed for poorly soluble chemicals.