A Guideline Value for Dioxin-Like Compounds in Marine Sediments

Area of Science:

• Environmental Chemistry
• Ecotoxicology
• Marine Biology

Background:

• Dredged sediments from Sydney harbor contained dioxin-like compounds, necessitating an ocean disposal guideline.
• Existing methods for deriving sediment quality guideline values (SQGV) had uncertainties, particularly those using field effects or sediment-pore water partitioning.
• A robust SQGV was required to assess the suitability of sediments for ocean disposal.

Purpose of the Study:

• To establish a defensible sediment quality guideline value (SQGV) for dioxin-like compounds in Sydney harbor sediments.
• To ensure the protection of aquatic biota from contaminants during ocean disposal.
• To develop a transferable methodology for similar international situations.

Main Methods:

• Utilized a tissue residue approach based on equilibrium partitioning between sediment and aquatic organisms.
• Employed tissue concentrations in fish, identified as the most sensitive biota.
• Incorporated biota-sediment accumulation factors and data from Sydney Harbor fish and sediments.

Main Results:

• A conservative SQGV of 70 pg toxic equivalent (TEQ)/g dry weight was calculated for dioxin-like compounds.
• This value is considered adequately protective of aquatic biota exposed to contaminants in ocean spoil grounds.
• The tissue residue approach offered greater certainty compared to effects data or pore water partitioning.

Conclusions:

• The developed SQGV of 70 pg TEQ/g dry weight is suitable for the ocean disposal of Sydney harbor sediments.
• The tissue residue approach provides a reliable and transferable method for setting sediment quality guidelines.
• This study contributes to the safe management of marine sediments and protection of aquatic ecosystems.