Distribution of hydrophobic organic contaminants in marine sediment fines-An alternative normalization strategy?

The necessary normalization of contaminant concentrations, in order to be able to compare contaminant content in sediments with different sediment properties, is currently not standardized within environmental monitoring and assessment programs. Therefore, this study investigates an alternative normalization strategy for hydrophobic organic contaminants (HOCs) by removing the coarse and chemically inert sediment fraction using an improved, half-automated wet-sieving method. We compare the results to commonly used TOC normalization (2.5% total organic carbon [TOC], OSPAR). Simultaneously, the study provides a comprehensive overview of HOC concentrations in sediment fines (<63 µm) for the German Exclusive Economic Zone and therefore gathers information about the more bioavailable and mobile part of the sediment that particularly accumulates HOCs due to its high surface area. We analyzed bulk sediment samples and their corresponding fine grain fractions from 25 stations in the German Exclusive Economic Zone for 41 HOCs including polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and organochlorine pesticides. The results indicate that the wet-sieving procedure is capable of physically normalizing the concentrations of the investigated HOCs and is useful for the comparison of concentrations in different sediment types. The wet-sieving procedure is more time consuming than the normalization to the TOC content. However, it offers the possibility of lowering the detection limits (LODs) through the analytical sample preparation procedure used, as sieving concentrates the contaminants. Therefore, a higher number of results >LOD were detected in sediment fines, leading to more informative data sets. In contrast to the commonly used normalization to 2.5% TOC, the statistical analyses carried out (principal component analysis with subsequent cluster analysis) additionally indicate that physical normalization allows better differentiation of sampling sites by contaminant sources and geographic location rather than their sediment characteristics. Integr Environ Assess Manag 2023;19:1348-1360. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Using the HPTLC-bioluminescence bacteria assay for the determination of acute toxicities in marine sediments and its eligibility as a monitoring assessment tool.

For an integrated ecological risk assessment of marine sediment contamination, the determination of target-compound concentrations by e.g. mass spectrometric methods is not sufficient to explain sediment toxicity. Due to the presence of a multitude of environmental contaminants in this complex matrix causing a mixed toxicity, the identification and assessment of main toxicants is a challenge. One approach in identifying main toxicants is the application of effect-directed analysis (EDA). In this study, an EDA approach was developed using high performance thin layer chromatography (HPTLC) coupled to bioluminescence bacteria detection with Aliivibrio fischeri for the determination of marine sediments acute toxicity. In a first attempt, the HPTLC separation was optimized with a fast, two-step gradient to separate main hydrophobic organic contaminant (HOC) classes found in marine sediments. An easy-to-use evaluation script for the resulting bioluminescence inhibition images was programed using R. The developed method was applied to sediment extracts of two different sample sets: (i) Fourteen marine sediment samples from the German Bight representing a wide range of contaminant loads and sediment properties and (ii) sediment samples from a core representing temporal trends of contamination. Results from the HPTLC-bioluminescence bacteria assay were compared to HOC concentrations determined by GC-MS/MS. A correlation of the determined inhibition Γ-values for the PAH inhibition zone to PAH concentrations showed a very good agreement (R2 = 0.91). The results of this study were used to evaluate the suitability of the EDA approach to be used as an assessment tool for marine sediments.