THESIS APPROVAL
THESIS APPROVAL
THESIS APPROVAL
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et al., 1994b), in dosed sediments aged less than 1 w. Based on these documents, it<br />
may be concluded that the reduced uptake of naphthalene from sediment by<br />
L. hoffmeisteri in this study might be occurred after 24 h of the exposure period.<br />
The result in the present study corroborates with those of previous studies<br />
concerning the rapid loss of naphthalene from the tissue of many organisms. Bates<br />
et al. (1997) observed that when naphthalene contaminated invertebrates were<br />
transported to uncontaminated waters, it was found to depurate rapidly from 24 h to<br />
few weeks based on the life stages and exposure concentration. This finding was also<br />
confirmed in the laboratory studies using annelids. Brunson et al. (1998) reported<br />
that naphthalene tissue residues of freshwater oligochaete Lumbriculus variegatus<br />
generally peaked by the starting and tended to decline to the end of the<br />
bioaccumulation test. Harmoniously, accumulation of naphthalene from sediment by<br />
marine worm Arenicola marina was rapid and almost complete depuration of the<br />
accumulated naphthalene was observed after 24 h (Lyes, 1979). By comparing with<br />
other higher molecular weight PAHs, the loss was shown in the same trend with<br />
decreasing of such compounds but the elimination was appeared later. For example,<br />
the parent compound of pyrene and benzo (a) pyrene accumulated in Lumbriculus<br />
variegatus was depurated within 72 h in clean sediment (Leppanen and Kukkonen,<br />
2000b). These supported evidences could be implied that high elimination of<br />
naphthalene was possibly caused the rapid loss of this chemical from the tissue of<br />
organisms.<br />
Mean tissue residue of naphthalene reported here for L. hoffmeisteri in the<br />
96 h sediment exposure was 1038±564.56 µg/g dwt with mean BAF value of<br />
31.97±17.01. These values are considerably higher than that reported for other<br />
annelids species exposed to the higher molecular weight PAHs. Nevertheless, time<br />
for exposure in this study is distinctly different from the previous reports due to short<br />
test period. For instance, the estuarine oligochaete Monopylephorus rubroniveus<br />
accumulated fluoranthene-contaminated sediments with tissue residues and BAFs<br />
ranged from 5,127-6,431 µg/g dwt and 23.0-1.6, respectively, in the 223-3,912 µg/g<br />
treatment by the 10 d exposure (Weinstein et al., 2003). The tube-dwelling spionid<br />
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