Improved ecological risk assessment of phenol in sediments via species sensitivity distribution and equilibrium...

Phenol is a water-soluble contaminant frequently detected in sediments, yet sediment-specific toxicity data are scarce. To address this data gap, we evaluated the use of water-based toxicity data for sediment ecological risk assessment (ERA) by combining the equilibrium partitioning method (EPM) with species sensitivity distributions (SSDs). Acute and chronic toxicity data from laboratory and artificial-stream tests using native aquatic species were compiled and converted to sediment-equivalent values for SSD construction. We quantified how species origin (native vs. foreign), habitat type (benthic vs. non-benthic), taxonomic composition, and sample size affect SSD-derived hazardous concentration for 5% of species (HC₅). Inclusion of benthic taxa, including early life-stage amphibians classified as benthic, was associated with lower HC₅ estimates; sensitivity differences across groups were generally < one order of magnitude. At least 8 species were needed for stable SSD performance. Applying an assessment factor to the HC₅ yielded a PNEC_sediment of 0.81 µg/g dry weight. Using this value, phenol concentrations from 23 monitoring sites indicate that 87% of locations would be categorized as moderate to high risk. As a phenol case study, the EPM-SSD framework demonstrates a pragmatic, transparent route to sediment ERA for moderately hydrophilic substances under data-limited conditions.