Partitioning-Based Dosing: An Approach To Include Bioavailability in the Effect-Directed Analysis of Contaminated Sediment Samples

Abstract

One of the major challenges of effect-directed identification of hazardous chemicals in sediments is the appropriate consideration of bioavailability for a hazard-based prioritization of fractions and toxicants. The equilibrium partitioning approach is frequently used to estimate the bioavailability of sediment contaminants. To simulate partitioning ofthe constituents of complex sediment contaminations in the sediment-water-biota system, a new dosing technique based on silicone elastomer stirrer bars (silicone rods) for use in a growth inhibition test with the green algae Scenedesmus vacuolatus was developed. The dosing technique has a high loading capacity and a fast achievement of equilibrium (5-50 min) for a broad range of model compounds. The subsequent delivery of compounds stored by the silicone during the bioassay compensates possible losses of compounds and keeps the concentrations constant. Furthermore, a dose-dependent response is achieved for single compounds and complex mixtures from sediment extracts. The extracts of three sediment samples from the Elbe River Basin were fractionated using a multistep HPLC method and investigated in the bioassay using conventional DMSO dosing and loaded silicone rods. The results of the toxicity test clearly show that the toxicity patterns are quite different for the two dosing techniques, whereas the differences between the sampling locations are less pronounced. We suggestthat partitioning-based dosing better reflects exposure in sediments and thus provides a more realistic identification of key toxicants.

Passive dosing of triclosan in multigeneration tests with copepods – stable exposure concentrations and effects at the low μg/L range

“…The applicability of passive dosing in experimental ecotoxicology has been demonstrated in a large number of studies [6,[8][9][10][11][12][13]. Silicone polymers are favorable to use in passive dosing because of the high diffusion coefficients of organic chemicals in silicone compared with other materials [14].…”

Measuring the toxicity of alkyl-phenanthrenes to early life stages of medaka (Oryzias latipes) using partition-controlled delivery

“…Poly(dimethyl siloxane) (PDMS)-coated glass fibers [10], silicone rods [11], and silicone cast into glass vials [12,13] were used to partition test compounds into the liquid phase of a bioassay. The method used in the present study, partition-controlled delivery (PCD), has been devised for chronic embryo toxicity assays with eggs from Japanese medaka (Oryzias latipes) [14].…”

Modelkey

“…Finally, the components of the toxic fractions are analytically identified, quantified and confirmed as the cause of the effect. MODELKEY developed an extensive integrated toolbox for EDA including tools for exhaustive and bioaccessibility-directed extraction (Schwab and Brack 2007), clean-up and fractionation tools (Lübcke-von Varel et al 2008;Meinert et al 2010), biotests and bioavailability-directed dosing techniques (Bandow et al 2009), and analytical and computer tools for structure elucidation . We applied this toolbox to sediments and waters at several sites in the three river basins mentioned above.…”