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 polychlorinated biphenyl (PCB) bioaccumulation from Lake Erie region sediments was studied using polydimethylsiloxane (PDMS) coated fibers and Dow Corning (DC) silicone coated jars, both with ex situ mixing (i.e., agitation). Polymers equilibrated with the sediments were compared to bioaccumulation in blackworms (Lumbriculus variegatus), exposed to the sediments for 28 days. Sediments were from Cleveland Harbor, Ashtabula Harbor (Ohio, USA), and Buffalo River (New York, USA). The sediment from Ashtabula was amended with activated carbon (AC). 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’ (lipid concentration ≈ 20 × PDMS concentration), but the relation was still strong (r² = 0.87). Different doses of AC were mixed into Ashtabula sediment in the laboratory, corresponding to 1 %, 10 %, and 100 % of the native total organic carbon (TOC). Based on PCB concentrations in DC silicone, a target AC dose equal to 10 % of the TOC would substantially reduce (∼62 %) bioaccumulation of the more hydrophobic PCBs (log octanol–water partition coefficient > 6) 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.