Sorption of polycyclic aromatic hydrocarbons into liposomes (artificial cell membranes) and the effects of dissolved natural organic matter

Dissolved natural organic matter (NOM) occurs widely in the aquatic environment and affects the fate of microorganic pollutants (e.g. intake, accumulation, movement, degradation, toxicity). The effect of NOM on the intake into biota (living cells) is very important. In the present study, the effects of coexisting NOM on the intake of microorganic pollutants into aquatic biota were experimentally evaluated. The NOM was concentrated from Lake Biwa water using a reverse osmosis filtration membrane. Two polycyclic aromatic hydrocarbons (PAH; pyrene and phenanthrene) were used as representative microorganic pollutants. Liposomes were synthesized in the laboratory to simulate living cell membranes and were used to investigate the intake of microorganic pollutants into aquatic biota. The experimental results (PAH onto NOM, NOM into liposomes, and PAH into liposomes) indicated that the sorption of PAH into liposomes was suppressed, apparently by PAH binding with NOM in the aqueous phase. This suggests that the accumulation and/or toxicity of microorganic pollutants can be retarded by NOM in the aqueous environment. Moreover, the experimental results indicated that sorption into liposomes (the liposome/water sorption coefficient, K_lipw) could be a better parameter for estimating the intake of microorganic pollutants into aquatic biota than the n-octanol/water partition coefficient (K_ow) in the aqueous environment.