Semipermeable membrane devices used to estimate bioconcentration of polychlorinated biphenyls

Aquatic organisms passively accumulate hydrophobic organic compounds, such as polychlorinated biphenyls, even when ambient water concentrations of the contaminant are below analytical detection limits. However, contaminant co ncentrations in tissue samples are subject to an inherently high level of v ariability due to differences in species, life stage, and gender bioconcent ration potentials. Semipermeable membrane devices (SPMDs) were used to samp le Aroclor 1254, a mixture of readily bioconcentrated polychlorinated biphe nyls (PCBs), in a contaminated wetland near Flat Top, WV. The devices consi sted of triolein, a lipid found in fish, enclosed in a polyethylene membran e. SPMDs were deployed in the water column and in direct contact with wetla nd sediments along a previously identified concentration gradient of PCBs. The devices were retrieved after a 25-day exposure period. Analytes were re covered by dialyzing the devices in nanograde hexane. Hexane dialysates wer e condensed and analyzed by gas chromatography. All deployed devices seques tered quantifiable amounts of Aroclor 1254. Water-column SPMDs accumulated PCBs far in excess of ambient water concentrations. The devices contacting sediments accumulated PCBs at all sites, though accumulated concentrations did not exceed concentrations in sediment. Patterns of PCB concentration in the devices corresponded to the identified gradient at the site. Results f rom the water-column SPMDs were used to estimate the concentration of the d issolved, bioavailable fraction of PCBs present in the water column. These concentrations ranged from 0.01 to 0.09 mu g/L of bioavailable Aroclor 1254 .