• Polycyclic aromatic hydrocarbons;
  • Sediment;
  • Mortality;
  • Toxic unit model


At a creosote-contaminated site, 33 individual polycyclic aromatic hydrocarbon (PAH) compounds were quantified in sediment and interstitial water (IW) at 30 stations. These compounds included the 13 parent PAHs from the ΣPAH model, 7 additional parent, and 13 alkylated compounds. Fourteen groups of alkylated compounds were also quantified in sediment extracts. Amphipod mortality using the ΣPAH model was predicted within ±10% of the observed when freely dissolved concentrations of PAHs with log Kows < 6.0 were used in the calculation of toxic units (TUs). The TUs computed from bulk sediment tended to overestimate the observed distribution of mortality. Although present, alkylated PAHs did not contribute significantly to the observed toxicity that was dominated by parent PAHs. The dominant parent compounds were in equilibrium with the interstitial water and sediment at the most contaminated stations (>500 ppm dry). However, most compounds were not in equilibrium with the sediment at stations with lower bulk concentrations but were in equilibrium with dissolved organic matter throughout the study area.