Bioconcentration of persistent organic pollutants in four species of marine phytoplankton.

The uptake of polychlorinated biphenyls (PCBs) was studied in four species of marine algae. A novel experimental system to establish and maintain constant dissolved concentrations of PCBs was employed. Headspace sampling was used to verify that the freely dissolved concentrations remained constant with time. The headspace analysis also allowed sorption to dissolved organic carbon (DOC) to be quantified for all but the most lipophilic PCB congeners. Equilibration with the dissolved phase was rapid for three of the four algae species (<1 d for the majority of congeners). Organic carbon-normalized algae/water partition coefficients (KAlgW) were similar for three of the four species, but were lower by a factor of 10 to 20 for Phaeodactylum tricornutum. The KAlgW values of the first three species were similar to the octanol/water partition coefficient (Kow) for those PCB congeners for which DOC sorption could be quantified. These KAlgW values also agreed well with organic carbon-normalized bioconcentration factors for PCBs in suspended particulate matter (BCF(SPM)) sampled in Baltic Sea surface water during the summer.

Stir bar contamination: a method to establish and maintain constant water concentrations of poorly water-soluble chemicals in bioconcentration experiments.

A novel experimental system to establish and maintain constant dissolved concentrations of poorly water-soluble compounds for bioconcentration experiments with algae was developed. Although still recommended in the literature as a "non-adsorptive" material, a commercially available Teflon stir bar that was preloaded with polychlorinated biphenyls (PCBs) proved to be an effective donor for partitioning controlled delivery. When placed in a bioconcentration test chamber, the PCB concentrations in water and in the headspace remained constant for up to 8 days. Henry's law constants determined in experiments using water only were in good accordance with values found in the literature, indicating that the chemical was truly dissolved. When algae (Emiliana huxleyi, class prymnesiophyceae) were added to the chamber, the water and air concentrations varied initially but stabilised within several hours, and smooth uptake curves were obtained for the algae. This indicates that the contamination system compensates for chemical loss from the water column. In addition, the Henry's law constants and the headspace measurements were used to estimate what fraction of the PCB in filtered water was associated with dissolved organic carbon, opening the opportunity to constrain one of the major artefacts in bioconcentration experiments.