Buried oil residues in selected beaches that were heavily contaminated by the 1989 Exxon Valdez Oil Spill (EVOS) continue to leach oil-contaminated suspended particulate material (SPM) and dissolved-phase polycyclic aromatic hydrocarbons (PAH) into interstitial- and near-shore waters. Both are bioavailable forms of hydrocarbons that can be absorbed or consumed. On selected intertidal beaches in Prince William Sound (PWS) during June 2002, nearshore- and interstitial-water samples were collected during outgoing tides, first from a water depth of 10–15 cm above undisturbed sediments at water's edge and then from pits dug just above the waterline. At the time of collection, all samples were vacuum-filtered through 0.7-µm pore-size, glass-fiber filters using a Portable Large Volume Water Sampling System (PLVWSS) to separate dissolved- and oil-contaminated SPM fractions for detailed hydrocarbon analyses and fingerprinting.

From intertidal pits at oil-impacted sites, interstitial water and SPM displayed strong oil signatures and elevated (albeit variable) PAH and n-alkane levels compared to the trivial non-petrogenic signatures seen at the reference sites. The dissolved-phase samples at the oil-impacted sites were typically characterized by water-soluble, lower-molecular-weight PAH, while the SPM/oil-phase contained the relatively-insoluble, higher-molecular-weight PAH and n-alkanes. Water's-edge samples (collected before any pits were excavated) typically showed a diluted- and degraded-compositional signature traceable to the interstitial water from higher tide levels. Interstitial-water dissolved-phase concentrations (average 1,200 ng/L.; 76–4,600 ng/L vs. 18–27 ng/L for reference sites) were above those reported to cause impacts to herring and salmon eggs (<1,000 ng/L; Rice et al., 2001). At reference sites, the water's edge samples matched the interstitial water with very low, non-petrogenic signatures. A recent diesel spill at a nearby site showed dissolved-phase patterns similar to those at the current EVOS sites.

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