Passive samplers as a proxy for the internal exposure of freshwater organisms

Wernicke, Theo; Birnbaum, Annika (Thesis advisor); Schäffer, Andreas (Thesis advisor)

Aachen : RWTH Aachen University (2022, 2023)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2022


Bioaccumulation of hydrophobic organic compounds (HOCs) in aquatic food webs is a major environmental concern. HOCs accumulated in biota can reach toxic levels, leading to adverse health effects in individuals and ecosystems. Fish as top predators are especially vulnerable for contamination with bioaccumulative HOCs and hence are subject of monitoring programs, in order to characterize the associated risks. However, large variability in HOC accumulation among individuals of one or different species has to be accounted for. To achieve this, considerable numbers of organisms have to be sampled on a regular basis, which raises ethical and financial issues. This situation calls for an alternative monitoring approach with a more robust concept, that circumvents large variability between individuals. Passive sampling devices (PSDs) offer a chemical activity-based approach for the assessment of pollutant enrichment from different abiotic environmental compartments with a subsequent estimation of bioaccumulation in fish or invertebrates. The first part of this work aimed to explore the potential of suspended particulate matter (SPM) to serve as a representative phase for HOC accumulation in bream and zebra mussels from different German rivers and to show the advantages of PSDs as a monitoring tool. In a second part, the potential of PSDs in water and SPM as a proxy for the internal exposure of different fish species was studied. For both approaches, muscle tissue of different fish or the whole soft tissue of zebra mussels was extracted using traditional exhaustive solvent extraction. The lipid-normalized concentrations of HOCs were determined and compared to total extracts from SPM (organic carbon-normalized) or the calculated corresponding concentrations in model lipids derived from PSDs in SPM or water. The results show that HOCs in SPM can have different levels of bioavailability, thus chemical activity-based sampling with PSDs should be preferred to total extraction methods to estimate the concentration in the lipid phase of biota. In most cases, lipids in bream and zebra mussel did not reach thermodynamic equilibrium with SPM, which makes the chemical activity-based sampling of SPM a conservative proxy for biota. However, in some cases, old bream exceeded the equilibrium partitioning concentration with SPM. This observation was explored in more details in the second study: top predatory fish of large size exceeded the equilibrium with SPM and water as a result of biomagnification. The PSD-based data from SPM proved to be a more conservative estimator for HOCs accumulated in fish than those from water. The body length of the fish was found to be more suitable to describe increasing accumulation of HOCs than their trophic level as derived from stable isotope analysis in the studied areas. By combining chemical activity-based sampling in the abiotic environment, the translation into corresponding concentrations in model lipids and body length as an indicator for increasing bioaccumulation in fish, a robust approach that has the potential to be complementary to conventional monitoring methods, was established.