Bioavailable Environmental Pollutant Patterns in Sediments from Passive Equilibrium Sampling

Sediment-associated risks depend
on the bioavailable fraction of
organic chemicals and cannot be comprehended by their total concentrations.
The present study investigated contamination patterns of bioavailable
chemicals in sediments from various sites around the globe by using
passive equilibrium sampling. The extracts had been characterized
previously for mixture effects by in vitro reporter gene assays and
were in this study analyzed using gas chromatography-high resolution
mass spectrometry for 121 chemicals including both legacy and emerging
contaminants. The spatial distribution of the detected chemicals revealed
distinct contamination patterns among sampling sites. We identified
compounds in common at the different sites but most contaminant mixtures
were site-specific. The mixture effects of the detected chemicals
were predicted with a mixture toxicity model from effect concentrations
of bioactive single chemicals and detected concentrations, applying
a joint model for concentration addition and independent action. The
predicted mixture effects were dominated by polycyclic aromatic hydrocarbons,
and among the chemicals with available effect data, 17% elicited oxidative
stress response and 18% activated the arylhydrocarbon receptor. Except
for two sites in Sweden, where 11 and 38% of the observed oxidative
stress response were explained by the detected chemicals, less than
10% of effects in both biological end points were explained. These
results provide a comprehensive investigation of bioavailable contamination
patterns of sediments and may serve as an example of employing passive
equilibrium sampling as a monitoring technique to integrate the risk
of bioavailable sediment-associated chemicals in aquatic environments.