Comparison of 1996 and 2009 Data for Pearl Harbor Sediment and Fish Tissue

摘要

Sediment and fish-tissue samples were collected from locations throughoutthe 5,000-acre Pearl Harbor (Oahu, Hawaii) site in 2009 for a follow-on CERCLAremedial investigation of the harbor’s sediment. Data from a 1996 remedial investigationsampling effort had indicated that sediments in some areas of the harbor pose unacceptablerisk to human and ecological receptors, but that dataset focused on 209 surface(upper 2 cm) sediment samples and fish samples from 15 locations. The 2009 effortcollected surface and subsurface discrete core samples and surface composite sedimentsamples from 74 locations; fish-tissue samples from 23 locations collocated with thesediment sampling locations; and sediment transport measurements for modeling thedepositional or erosional characteristics of the harbor.The highest exceedance rates and maximum concentrations in both sediment and fishtissuesamples were reported from two of the harbor’s five geographic areas: SoutheastLoch and Navigation Channel. Assessment of temporal variations through comparison ofcollocated 2009 and 1996 surface-sediment analytical results showed that, although the2009 data indicate the continued presence of contaminated surface sediments in Shipyard(Southeast Loch), Navigation Channel, and portions of East Loch, concentrations ofcontaminants have decreased significantly over the 13 years between the two samplingevents. These decreases may be associated with reduction of land-based contaminantsources and with the deposition since 1996 of relatively clean sediments from the harbor’stributary streams. Comparison of fish-tissue data for the collocated 2009 and 1996samples suggests that concentrations of most metals, total polychlorinated biphenyls(PCBs), pesticides, and dioxins (polychlorinated dibenzo-p-dioxins [PCDDs] and polychlorinateddibenzo-p-furans [PCDFs]) in Pearl Harbor fish tissues have also decreasedsignificantly since 1996. The location-specific data, combined with evaluation of collocatedsurface sediment and sediment-core analytical results, enabled identification of themost significant historical and potentially continuing sources of sediment contaminationfor each region of the harbor.The results generally confirmed lower overall levels of contaminants in the harborand were used to identify specific areas warranting further consideration. The need forremedial actions for sediment in specific areas of the harbor identified for further considerationwill be evaluated in the project’s follow-on feasibility study (FS).