Bioaccumulation in Functionally Different Species: Ongoing Input of PCBs with Sediment Deposition to Activated Carbon Remediated Bed Sediments

Activated carbon (AC) amended bed sediments reduced total polychlorinated biphenyl (PCB) accumulation in three functionally different marine species, sandworms (Alitta virens), hard clams (Mercenaria mercenaria), and sheepshead minnows (Cyprinodon variegatus), during both clean and contaminated ongoing sediment inputs. Mesocosm experiments were conducted for 90 days to evaluate native, field-aged bed sediment PCBs and ongoing input PCBs added thrice a week. Simulated in situ remediation applied an AC dose equal to the native organic carbon content, which was pre-mixed into the bed sediment for one month. The highest bioaccumulation of native PCBs was in worms, which remained in and directly ingested the sediment, whereas the highest bioaccumulation of the input PCBs was in fish, which were exposed to the water column. When periodic PCB contaminated sediment inputs were introduced to the water column, the AC remedy had minimal effect on the input PCBs, while the native bed PCBs still dominated bioaccumulation in the control (no AC). Therefore, remediation of only the local bedded sediment in environmental systems with ongoing contaminant inputs may have lower efficacy for fish and other pelagic and epibenthic organisms. While ongoing inputs can continue to obscure remedial outcomes at contaminated sediment sites, this study showed clear effectiveness of AC amendment remediation on native PCBs despite these inputs, but no remediation effectiveness for the input-associated PCBs (at least within the study duration).