Test of Sigma polycyclic aromatic hydrocarbon model at a creosote-contaminated site, Elliott Bay, Washington, USA

At a creosote-contaminated site, 33 individual polycyclic aromatic hydrocar bon (PAH) compounds were quantified in sediment and interstitial water (IW) at 30 stations. These compounds included the 13 parent PAHs from the Sigma PAH model, 7 additional parent, and 13 alkylated compounds. Fourteen group s of alkylated compounds were also quantified in sediment extracts. Amphipo d mortality using the Sigma PAH model was predicted within +/-10% of the ob served when freely dissolved concentrations of PAHs with log K(ow)s < 6.0 w ere used in the calculation of toxic units (TUs). The TUs computed from bul k sediment tended to overestimate the observed distribution of mortality. A lthough present, alkylated PAHs did not contribute significantly to the obs erved toxicity that was dominated by parent PAHs. The dominant parent compo unds were in equilibrium with the interstitial water and sediment at the mo st contaminated stations (>500 ppm dry). However, most compounds were not i n equilibrium with the sediment at stations with lower bulk concentrations but were in equilibrium with dissolved organic matter throughout the study area.