19 Aug 2025

Bioaccumulation in Fish (Cyprinodon variegatus) During Rejuvenations of a Thin Active Cap over Field-Aged PCB Contaminated Sediment: The Effect of Clean Versus Contaminated Ongoing Influx

Abstract: Repeated addition of activated carbon (AC) via the water column was applied to rejuvenate sorption capacity of thin AC-amended sand caps placed over polychlorinated biphenyl- (PCB) contaminated marine bed sediment receiving ongoing input of sediment (contaminated or clean) in mesocosms. Bioaccumulation of PCBs in sheepshead minnows (Cyprinodon variegatus) from bed sediment was reduced by repeated application of reju-venating AC when the ongoing input was contaminated. However, when the input sediment was clean, the novel AC addition increased fish uptake of bedded PCBs in the first 60-days of the 90-day experiments. The 79 % increase of bedded PCB bioaccumulation in fish, for clean versus contaminated inputs, was statistically signifi-cant (p < 0.05) in experiments where the rejuvenating AC was applied. Equilibrium concentrations in low- density polyethylene (LDPE) passive samplers did not fully explain bioaccumulation. Field implications of this research include setting appropriate temporal expectations of this novel remediation strategy regarding the primary desired effect (i.e., PCB bioavailability reductions).

7 Aug 2025

Thermodynamic Exposure Reductions of PCBs Available to Lumbriculus variegatus in Lake Erie Region Sediments Amended with Activated Carbon

Abstract: A chemical activity-based assessment of PCB bioaccumulation from Lake Erie region sediments was studied using polydimethylsiloxane coated fibers and Dow Corning silicone coated jars. Polymers equilibrated with the sediments were compared to bioaccumulation in blackworms, exposed to the sediments for 28 days. Sediments were from Cleveland Harbor, Ashtabula Harbor, and Buffalo River. Sediment from Ashtabula was amended with activated carbon. Using lipid-polymer partition coefficients, the polymers were able to estimate actual bioaccumulation in worms, with close to a 1:1 relationship and r2 = 0.94. If lipid normalized worm bioaccumulation was compared to equilibrated PDMS concentrations, there was a 20:1 ‘off-set,’ but the relation was still strong. Different doses of AC were mixed into Ashtabula sediment in the laboratory, corresponding to 1 %, 10 %, and 100 % of the native total organic carbon. Based on PCB concentrations in DC silicone, a target AC dose equal to 10 % of the TOC would substantially reduce bioaccumulation of the more hydrophobic PCBs from Ashtabula Harbor dredged material. Widespread AC amendment to surficial sediment of the eastern basin of Lake Erie may reduce the thermodynamic pressure of PCBs from that sediment source and allow for a continued decline in fish tissue concentrations.