Spiking organic chemicals onto sediments for ecotoxicological analyses: an overview of methods and procedures

Improving Sediment Toxicity Testing for Very Hydrophobic Chemicals: Part 1—Spiking, Equilibrating, and Exposure Quantification

“…However, it should be stressed that only artificial sediment was tested in the present study and that any effects of equilibration time may, to some extent, be dependent on the type of sediment (You et al, 2009). Interestingly, the above plea for intensive mixing clearly contradicts the recommendation by Picone et al (2022) to perform equilibrations statically so as not to disturb partitioning. Likewise, the USEPA (2000) recommends an equilibration period of at least 2 months for VHOCs (i.e., chemicals with log K OW greater than 6), but if performed statically, 2 months may actually even be too short, in particular at low temperatures (4 °C), at which aqueous solubilities and diffusion rates are further reduced.…”

“…In prospective testing, VHOCs generally are introduced (spiked) into sediment through one of the following methods: (1) spiking directly in a slurry with or without a carrier solvent (direct spiking); (2) spiking via a solvent on the wall of a container and subsequent evaporation of the solvent and mixing (rolling) with the sediment sample (glass coating); or (3) spiking a small subsample of sediment (sand) and subsequent evaporation of the spike solvent and mixing the subsample with the full mass of sediment (sand coating). Some of these methods are also referred to as, for example, solvent, conventional, shell, and dilution mixing (Hiki et al, 2021a; Northcott & Jones, 2000a; Picone et al, 2022). The third method is recommended by the OECD for spiking chemicals to sediment (OECD, 2004, 2007).…”

When and How to Conduct Ecotoxicological Tests Using Natural Field‐Collected Sediment

“…Such properties may also affect the choice of contaminant solvent. For contaminants of low water solubility, water is seldom a viable choice (Picone et al, 2022). Organic compounds with low water solubility and high hydrophobicity (high log K OW ; i.e., polychlorinated biphenyls, polyaromatic hydrocarbons, and some phosphatidylcholines) often requires an organic solvent (e.g., acetone, methanol, hexane, or dimethyl sulfoxide) to be dissolved (see Méndez et al, 2001; Picone et al, 2022; Selck et al, 2003a).…”

“…For contaminants of low water solubility, water is seldom a viable choice (Picone et al, 2022). Organic compounds with low water solubility and high hydrophobicity (high log K OW ; i.e., polychlorinated biphenyls, polyaromatic hydrocarbons, and some phosphatidylcholines) often requires an organic solvent (e.g., acetone, methanol, hexane, or dimethyl sulfoxide) to be dissolved (see Méndez et al, 2001; Picone et al, 2022; Selck et al, 2003a). The choice of organic solvent depends on the solubility of the contaminant and the potential solvent impact on the test organisms (Picone et al, 2022).…”

“…A key challenge when working with any sediment system relates to the difficulties in comparing results among studies due to differences in the sediment base (i.e., sediment characteristics including grain size and type, organic matter [OM] content and quality, pH, background contamination) which may cause variations in, for example, compound partitioning and food availability (Picone et al, 2022). Although the majority of laboratory experiments use natural field-collected sediment (Picone et al, 2022), current OECD guidelines recommend artificially formulated sediment (see OECD, 2004OECD, , 2007OECD, , 2014, most likely due to the theoretically higher homogeneity. Though it has also been recognized that most test organisms do not thrive in artificially formulated sediment-a topic that was recently discussed at the Sediment Interest Group meeting at the Society of Environmental Toxicology and Chemistry, North America Conference, November 2022.…”