Comparing Equilibrium Concentrations of Polychlorinated Biphenyls Based on Passive Sampling and Bioaccumulation in Water Column Deployments

Abstract

Biomonitoring at contaminated sites undergoing cleanup, including Superfund sites, often uses bioaccumulation of anthropogenic contaminants by field-deployed organisms as a metric of remedial effectiveness. Bioaccumulation studies are unable to assess the equilibrium status of the organisms relative to the contaminants to which they are exposed. Establishing equilibrium provides a reproducible benchmark on which scientific and management decisions can be based (e.g., comparison with human dietary consumption criteria). Unlike bioaccumulating organisms, passive samplers can be assessed for their equilibrium status. In our study, over a 3-year period, we compared the bioaccumulation of selected polychlorinated biphenyls (PCBs) by mussels in water column deployments at the New Bedford Harbor Superfund site (New Bedford, MA, USA) to codeployed passive samplers. Based on comparisons to the calculated passive sampler equilibrium concentrations, the mussels were not at equilibrium, and the subsequent analysis focused on evaluating approaches for estimating equilibrium bioaccumulation. In addition, a limited evaluation of metal bioaccumulation by the exposed mussels and a metal passive sampler was performed. In general, mussel and passive sampler accumulation of PCBs was significantly correlated; however, surprisingly, agreement on the magnitude of accumulation was optimal when bioaccumulation and passive sampler uptake were not corrected for nonequilibrium conditions. A subsequent comparison of four approaches for estimating equilibrium mussel bioaccumulation using octanol-water partition coefficients (K OW ), triolein-water partition coefficients (K TW ), and two types of polymer-lipid partition coefficients demonstrated that field-deployed mussels were not at equilibrium with many PCBs. A range of estimated equilibrium mussel bioaccumulation concentrations were calculated, with the magnitude of the K OW -based values being the smallest and the polymer-lipid partition coefficient-based values being the largest. These analyses are intended to assist environmental scientists and managers to interpret field deployment data when transitioning from biomonitoring to passive sampling.

Quantitative thermodynamic exposure assessment of PCBs available to sandworms (Alitta virens) in activated carbon remediated sediment during ongoing sediment deposition

“…Previous researchers have also found biota to be under-equilibrated relative to sediments. [17][18][19][20] Recently, Burgess et al 38 performed a similar analysis at New Bedford Harbor under eld conditions. In that study, bioaccumulation of PCBs by mussels (Mytilus edulis) deployed in the water column was compared to accumulation by co-deployed LDPE passive samplers.…”

“…), and C lipid⇌polymer⇌media is the concentration in lipid at equilibrium with that media (often notation is simplified to C lipid⇌media ). The conversion used in the present study is the same as the “third approach” applied in Burgess et al , 38 and is the approach of Jahnke et al 18 and Schäfer et al 20…”

“…The conversion used in the present study is the same as the "third approach" applied in Burgess et al, 38 and is the approach of Jahnke et al 18 and Schäfer et al 20…”

“…22 The New Bedford Harbor site and sediment have been a focus of past and present contaminated sediment research. 1,2,21,34–38 The mesocosms included ongoing influx of ‘fresh’ clean or contaminated sediment and bioturbation as processes driving contaminant transport between AC remediated bed sediments and the water column. The objectives of this research were to perform a quantitative thermodynamic exposure assessment (‘QTEA’) of native bedded PCBs in mesocosms and sandworms ( Alitta virens ), with regard to: (1) the presence or absence of AC mixed into the bed sediment, (2) the presence or absence of spiked PCBs on the input sediment ( i.e.…”

“…22 The New Bedford Harbor site and sediment have been a focus of past and present contaminated sediment research. 1,2,21,[34][35][36][37][38] The mesocosms included ongoing inux of 'fresh' clean or contaminated sediment and bioturbation as processes driving contaminant transport between AC remediated bed sediments and the water column. The objectives of this research were to perform a quantitative thermodynamic exposure assessment ('QTEA') of native bedded PCBs in mesocosms and sandworms (Alitta virens), with regard to: (1) the presence or absence of AC mixed into the bed sediment, (2) the presence or absence of spiked PCBs on the input sediment (i.e., sediment introduced periodically to simulate ongoing deposition), and (3) the polymeric sampling method: in situ passive (pre-equilibrium) sampling with low density polyethylene (LDPE) (passive sampling devices, PSDs) or ex situ equilibrium sampling with silicone coated jars (equilibrium sampling devices, ESDs).…”