Abstract
BackgroundChemical quality of sediment and suspended particulate matter (SPM) is usually assessed by total chemical concentrations (Ctotal). However, the freely dissolved concentration (Cfree) is the ecologically more relevant parameter for bioavailability, diffusion and bioaccumulation. In recent studies, equilibrium sampling has been applied to determine Cfree of hydrophobic organic contaminants (HOCs) in the sediment pore water, whereas such data are missing for SPM. We applied solid-phase micro-extraction to measure and compare Cfree of PAHs and PCBs in pore water of sediments and SPM sampled along the German part of the river Elbe. Moreover, site-specific distribution ratios were evaluated and Cbio,lipid was predicted using Cfree.ResultsCfree of PAHs remained largely constant while Cfree of PCBs varied along the Elbe River. The highest Ctotal of PCBs and PAHs were found at Prossen (km 13) and Meißen (km 96). PCB Ctotal even exceeded the environmental quality standard for sediment and SPM in Prossen. Site-specific distribution ratios (KD) revealed a stronger sorption for PAHs compared to PCBs, indicating a higher availability of PCBs. Equilibrium partitioning concentrations in lipids (Clip↔sed) showed a high correlation with actually measured lipid-normalised concentrations (Cbio,lipid) in bream. This indicates that PCB bioaccumulation in this benthic fish species is closely linked to the sediment contamination.ConclusionsIn rivers, SPM functions as a transportation vehicle for HOCs along the stream until it eventually deposits to the sediment. This study demonstrates that due to weaker sorption of PAHs and PCBs to the SPM this matrix poses a higher risk to the aquatic environment compared to the sediment. The prediction of Cbio,lipid of PCBs was correct and shows that solid-phase micro-extraction is highly suited to predict lipid concentration, and thus a valuable tool for risk-assessment or sediment management.
Highlights
Chemical quality of sediment and suspended particulate matter (SPM) is usually assessed by total chemical concentrations (Ctotal)
The principle is based on Niehus et al Environ Sci Eur (2018) 30:28 a polydimethylsiloxane (PDMS)-coated glass fibre that is equilibrated in the sediment or SPM sample and directly measured using GC–MS [2]
In several studies equilibrium sampling using SPME fibres has been successfully applied to determine Cfree of hydrophobic organic contaminants (HOCs) in the sediment pore water [2, 6], whereas such data are missing for SPM
Summary
Chemical quality of sediment and suspended particulate matter (SPM) is usually assessed by total chemical concentrations (Ctotal). The freely dissolved concentration (Cfree) is the ecologically more relevant parameter for bioavailability, diffusion and bioaccumulation. Equilibrium sampling has been applied to determine Cfree of hydrophobic organic contaminants (HOCs) in the sediment pore water, whereas such data are missing for SPM. We applied solid-phase micro-extraction to measure and compare Cfree of PAHs and PCBs in pore water of sediments and SPM sampled along the German part of the river Elbe. In terms of the assessment of sediment or suspended particulate matter (SPM), the total concentration (Ctotal) is not the deciding factor when describing ecotoxicological impacts. To assess accessibility/bioavailability, diffusion or bioaccumulation, it is well known that the relevant parameter is the chemical activity (a).
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