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THESIS APPROVAL

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Leppanen and Kukkonen (1998b) investigated the relative importance of<br />

ingested sediment and pore water as sources of bioaccumulation routes for pyrene in<br />

Lumbriculus variegatus. The worms were exposed to radiolabeled pyrene spiked lake<br />

sediment for 28 d and the egestion rate was followed. The results showed that pyrene<br />

accumulated mainly (61% of the body burden) through ingested material and<br />

bioavailability was decreased when exposure time increase. The data signified the<br />

importance of ingested material in bioaccumulation of hydrophobic chemicals in<br />

Lumbriculus variegatus<br />

Leppanen and Kukkonen (2000a) studied the importance of sedimentchemical<br />

contact time in bioaccumulation of pyrene and benzo(a)pyrene to<br />

Lumbriculus variegatus. The results showed that increase in sediment-chemical<br />

contact time decreased pyrene and benzo(a)pyrene uptake clearance for both feeding<br />

and nonfeeding animals. Ingest of sediment considerably increased accumulation of<br />

both compounds indicating the importance of feeding behavior in bioaccumulation of<br />

sediment-associated chemicals.<br />

Leppanen and Kukkonen (2000b) studied bioaccumulation, depuration and<br />

biotransformation of radiolabelled pyrene and benzo(a)pyrene were studied in<br />

Lumbriculus variegatus in spiked Lake Mekrijarvi (Eastern Finland) sediment. The<br />

results showed that bioaccumulation of both chemicals was fast and an apparent<br />

steady level was reached with a week. Biotransformation results showed the relative<br />

proportion of parent compound in tissues decreased continuously during the exposure.<br />

Approximately 60% of pyrene and 90% of benzo(a)pyrene was still in the parent<br />

compound.<br />

Conrad et al. (2002) studied the effect of sediment-chemical contact time on<br />

routes of uptake in Lumbriculus variegatus using sediment spiked with 14 C-labelled<br />

pyrene. The results showed that there was a decline in bioavailability with time<br />

separated in 3 stages process, including a rapid initial decline (40% decreases) during<br />

the first period, an intermediate stage with stable levels, and an ultimate decline (70%<br />

decreases) at the end of the exposure. The dietary route of uptake for pyrene varied<br />

34

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