Abstract
In situ amendment of surface sediment with activated carbon (AC) is a promising technique for reducing the availability of hydrophobic organic compounds in surface sediment. This study evaluated the performance of a logistically-challenging AC placement in a high-energy hydrodynamic environment adjacent to and beneath a pier in an active military harbor. Measurements conducted pre-amendment and 10-, 21-, and 33-months post-amendment using in situ exposures of benthic invertebrates and passive samplers indicated that the targeted 4% (by weight) addition of AC (particle diameter ≤ 74 µm) in the uppermost 10 cm of surface sediment reduced PCB availability by an average (± standard deviation, SD) of 81% ± 11% in the first 10 months following amendment. The final monitoring event (33 months after amendment) indicated an approximate 90% ± 6% reduction in availability, reflecting a slight increase in performance and demonstrating stability of the amendment. Benthic invertebrate census and Sediment Profile Imagery did not indicate significant differences in benthic community ecological metrics among the pre- and three post-amendment monitoring events, supporting existing scientific literature that this approximate AC dosage level does not significantly impair native benthic invertebrate communities. Recommendations for optimizing typical site-specific assessments of AC performance are also discussed, and include quantifying reductions in availability and confirming placement of AC. This article is protected by copyright. All rights reserved
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