Using passive samplers to measure the bioavailability and transport of sedimentary organic contaminants

Polyethylene (PE) sampler uptake was compared to polychaete uptake to assess bioavailability of polychlorinated biphenyls (PCBs) from resuspended sediments in the laboratory. Disequilibrium-corrected PE were found to take up PCBs in nearly a 1:1 ratio with polychaete lipid (r2 = 0.88), demonstrating that PE samplers are good biomimetic tools in laboratory exposure tests. When dissolved concentrations were calculated based on equilibrium partitioning from both PE and lipid, PE were found to overestimate biota exposure by 3.6 times on average. PE samplers and polychaetes demonstrated that resuspension under varying water column redox conditions does not affect bioavailability of residual PCBs. In a separate experiment, PE samplers used to measure the water column during laboratory sediment resuspensions suggested dredging-induced resuspension causes an increase in partitioning of sedimentary PCBs to the aqueous phase. The fraction of release that was freely dissolved versus dissolved organic carbon (DOC)-associated depended on PCB physicochemical characteristics. PE samplers deployed in the field (Newark Bay, NJ) provided freely dissolved and gaseous concentrations of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) in the water column and atmosphere and indicated the direction of PCDD/F activity gradients. High surface water-air gradients were found for most PCDD/Fs analyzed, indicating Newark Bay is a source of PCDD/Fs to the New York/New Jersey atmosphere. Water colunm gradients were variable but generally close to one, suggesting the water column is well mixed with respect to PCDD/Fs. Porewater-water column gradients were also generally close to one for low MW PCDD/Fs, but greater than one in the direction of the water column for high MW PCDD/Fs, indicating that sediment porewater is a net source of high MW PCDD/Fs to the water column. The uptake of PCDD/Fs by PE samplers tumbled in the laboratory with Newark Bay sediment was compared to PCDD/F uptake by native biota collected from the Bay. PE- and lipid-based partitioning suggested that PE were underestimating the porewater concentrations that biota are exposed to by ∼3 times.