Derivation and application of effect-based trigger values for persistent and nonpersistent aryl hydrocarbon receptor-mediated activities in coastal sediments

This study establishes sediment effect-based trigger (EBT) values for aryl hydrocarbon receptor (AhR)-mediated activity using the H4IIE-luc assay, distinguishing between non-persistent and persistent agonists. Sediment-specific EBTs were derived for AhR-mediated activity by translating sediment quality guidelines (SQGs) into bioanalytical equivalent concentrations using relative effect potencies (REPs) determined in the H4IIE-luc assay. Compound-specific bioanalytical equivalents (BEQs) were calculated using SQGs and REPs. For persistent and non-persistent AhR activators, BEQs showed log-normal distributions, and their 50th percentiles were assigned as EBT-BEQchem. The EBT-BEQbio values were derived from EBT-BEQchem by multiplying with mixture factor (MF) derived from potency balance analysis to account for bioassay responses unexplained by quantified target compounds. The resulting EBT-BEQbio for non-persistent AhR-mediated activity dominated by polycyclic aromatic hydrocarbons (PAHs) was 470 ngBaP gdm-1 [expressed as benzo[a]pyrene equivalents (BaP-EQ)]. The EBT-BEQbio for persistent AhR-mediated activity was 7.4 pgTCDD gdm-1 [expressed as 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQ)], by considering polychlorinated dibenzo-p-dioxins and dibenzofurans, coplanar polychlorinated biphenyls, polybrominated diphenyl ethers, and PAHs. Comparisons between bioassay-derived bioanalytical equivalents (BEQbio) for Busan Bay sediments and previously published datasets revealed that BaP-EQbio and TCDD-EQbio frequently exceeded the derived EBTs for non-persistent and persistent AhR-mediated mixtures. The EBT-BEQchem values were exceeded in all cases by the predicted mixture effects of quantified chemicals BEQchem. Benchmarking BEQbio values from previous case studies against EBT-BEQbio showed that sediments from industrialized coastal and riverine regions frequently exceeded EBT-BEQbio thresholds, whereas remote or open-water sites generally remained below them. These findings demonstrate that sediment-specific AhR EBTs incorporating mixture correction provide environmentally relevant benchmarks for sediment quality assessment. The proposed framework enhances the interpretation of bioassay data and supports an integrated sediment quality assessment combining bioanalytical tools with chemical analysis.