Consensus sediment quality guidelines for polycyclic aromatic hydrocarbon mixtures

Sediment duality guidelines (SQGs) for polycyclic aromatic hydrocarbons (PA Hs) have been derived from a variety of laboratory, field, and theoretical foundations. They include the screening level concentration, effects ranges -low and-median, equilibrium partitioning concentrations, apparent effects threshold, Sigma PAH model, and threshold and probable effects levels. The resolution of controversial differences among the PAH SQGs lies in an under standing of the effects of mixtures. Polycyclic aromatic hydrocarbons virtu ally always occur in field-collected sediment as a complex mixture of covar ying compounds. When expressed as a mixture concentration. that is, total P AH (TPAH), the guidelines form three clusters that were intended in their o riginal derivations to represent threshold (TEC = 290 mu g/g organic carbon [OC]), median (MEC = 1.800 mu g/g OC). and extreme (EEC = 10.000 mu g/g OC ) effects concentrations. The TEC/MEC/EEC consensus guidelines provide a un ifying synthesis of other SQGs, reflect causal rather than correlative effe cts. account for mixtures, and predict sediment toxicity and benthic commun ity perturbations at sites of PAH contamination. The TEC offers the most us eful SQG because PAW mixtures are unlikely to cause adverse effects on bent hic ecosystems below the TEC.