Exploring the partitioning of hydrophobic organic compounds between water, suspended particulate matter and diverse fish species in a German river ecosystem

Abstract

Background Bioaccumulation of hydrophobic organic compounds (HOCs) along freshwater food chains is a major environmental concern as top predators in food webs are relevant for human consumption. To characterize and manage the associated risks, considerable numbers of organisms are sampled regularly for monitoring purposes. However, ethical and financial issues call for an alternative, more generic and more robust approach for assessing the internal exposure of fish that circumvents large variability in biota sampling due to interindividual differences. Passive sampling devices (PSDs) offer a fugacity-based approach for pollutant enrichment from different abiotic environmental compartments with a subsequent estimation of bioaccumulation in fish which we explored and compared to HOC concentrations in fish as determined using traditional approaches. Results In this study, concentrations in silicone-based PSDs applied to the water phase and suspended particulate matter (SPM) of a river polluted with HOCs were used to estimate the concentration in model lipids at thermodynamic equilibrium with either environmental compartment. For comparison, muscle tissue of seven fish species (trophic level 1.8 to 2.8) was extracted using traditional exhaustive solvent extraction, and the lipid-normalized concentrations of HOCs were determined. The PSD-based data from SPM proved to be a more conservative estimator for HOCs accumulated in fish than those from water. 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 and might offer a suitable alternative for future studies. Conclusions By combining fugacity-based sampling in the abiotic environment, translation into corresponding concentrations in model lipids and body length as an indicator for increasing bioaccumulation in fish, we present a suggestion for a robust approach that may be a meaningful addition to conventional monitoring methods. This approach potentially increases the efficiency of existing monitoring programs without the need to regularly sacrifice vertebrate species. Graphical Abstract

Chemometers: an integrative tool for chemical assessment in multimedia environments

“…Using a similar approach, other studies like the one from Smedes et al, 86 have compared chemometer-based concentrations in water and fish from different trophic levels, in this case applying PRCs to extrapolate concentrations obtained with kinetic sampling in water to equilibrium using the dissipation of PRCs. In other publications, like Wernicke et al 25 and Allan et al 104 the activity ratios were approximated using chemometers in the abiotic compartment (water and/or suspended particulate matter) in combination with exhaustive extraction in fish, followed by their translation into lipid-based concentrations, assuming model lipids at equilibrium with the abiotic compartment. Chen et al 37,38 recently developed another interesting approach to study the thermodynamics of biomagnification through the application of chemometers in food before and after passing the gastrointestinal tract (feces) of different zoo-based predator species.…”

“…Then, the sampling rate R s for each compound can be calculated as follows in eqn (5): R s = B / M 0.47 .Despite this approach working reasonably well for chemical analysis (with larger uncertainties when the degree of equilibration is low), 25 it cannot be applied when the extracts are to be submitted to bioanalytical profiling because of the differences in degree of equilibration of the unknown chemicals and the potential effects elicited by the PRCs, which is one of the drawbacks of this approach. Having an equilibrium chemometer for the water phase would open up not only for broad use of bioassays, but also for routine applications, e.g.…”

“…Suspended particulate matter (SPM) from aquatic environments has been studied likewise. [24][25][26] More recently, biota have been sampled with chemometers, 38,78,96 and nowadays, methods are established even for lean tissues, based on frequent mixing of the samples to avoid local depletion, that make it feasible to reach equilibrium within a reasonable time frame, i.e., before the tissue starts to decay. The methods were originally developed for fish muscle tissue and whole fish, 78,80 but have recently been adapted to include different organs and tissues of marine mammals 75 and humans.…”