engleski

Ecotoxicological assessment of contaminated Mediterranean dredged sediments after remediation

The management of dredged sediments is a priority issue in the Mediterranean Sea where sediments are historically polluted by metals and organic compounds. This research investigated the possibility of reducing sediment toxicity via mixing composted contaminated dredged sediment batches to less contaminated ones, in order to provide useful tools for their final management and disposal. The ecotoxicological effect of these sediments was estimated by Microtox® solid phase, and leachates by SOS/umu–test and germination-test. Composted sediments originated from French Mediterranean navy harbour (A), commercial port (B) and two composite specimens (C and D) obtained after mixing various sediments were taken into consideration. EC50 values, expressed as g sediments per litre, followed the gradient: sample C (1.38 ± 0.19) < A (1.98 ± 0.32) ~ B (2.04 ± 0.42) < D (7.51 ± 2.90). Mixed samples (C and D) which have the same granulometry present significantly different EC50 that may be explained by contamination level in whole sediments. Sample C, which is a dilution of A, remains toxic, although the contamination level is lower than that of A, suggesting a granulometry effect (21% of fine particles in A versus 28 % in C). Sample D, which is a dilution of B, is less toxic. This may be due to the decrease of contamination level and fine particle percentage. Composting procedure allowed significant decrease in fine particle and organic pollutants, remediation performed by dilution of less contaminated sediments was successful only with the coarse sediments. For genotoxicity testing the sediments samples were extracted with deH2O (1:10 w/v ; 24h) according to standard method commonly applied to produce leachates for ecotoxicological analyses. Serial dilutions of lechates were used, with maximal sediment equivalent dose 33.33 g/L. The results of SOS/umu-test without metabolic activation of analyzed samples (A, B, C, D) were all negative (IR < 1.5), i.e. leachates (contamination) did not resulted with genotoxic activity/effects on used test bacteria. Germination-test using seeds of Flax (Linum usitatissimum L.) after 24 h treatment with 5 ml of leachates (equivalent to 0.5 g of sediment) ranged samples by increasing effect: Control (90.67 ± 2.79), D (90.00 ± 9.81%), B (85.00 ± 7.93), C (48.89 ± 6.94), A (44.00 ± 13.21).

Dredged sediment; Remediation; Microtox solid phase; SOS/umu–test; Germination-test

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