Comparison of methods used to determine the availability of polycyclic aromatic hydrocarbons in marine sediment

Semipermeable membrane devices (SPMDs), Tenax TA, and a polyethylene tube dialysis (PTD) methods were used to estimate the "available" fraction of PAH in marine sediment slurries. The polyethylene membrane used in the SPMD and PTD methods mimics a biomembrane. The PAH must diffuse through the membrane into triolein or pentane, respectively. The Tenax TA scavenges PAH from the water phase and is separated from the sediment, thus particle-associated PAH are excluded from all three methods. Spiked PAH were more readily available than endogenous (unspiked) PAH, and the presence of sediment organic matter decreased desorption and thus availability of the PAH. All three methods could aid in bioremediation feasibility assessments and predictions on the potential toxicity of sediments or soils. The SPMD method has the advantage of being available commercially, and the use of such a standard method allows comparison with other samples from the literature. The Tenax method gave similar results with the exception of the larger compounds that were recovered more efficiently, and it was less expensive. The PTD method was the most stringent assay for availability and could be useful in assessing the risk associated with exposure to a contaminated sample.