A methodological approach for ecotoxicological characterization of non-hazardous sediments for their beneficial reuse

Purpose In France, the beneficial reuse of sediments is conditioned upon a demonstration of environmental acceptability for each scenario. Such evidence has to be provided in application of the NF EN 12920 +A1 standard methodologies. Before the application of risk assessment methodology, the HP14 hazard property must be measured using specific bioassays. However, sediments may have ecotoxicological impacts despite a non-hazardous classification. The application of a battery of bioassays sensitive to non-hazardous sediments could allow to select sediments before choosing the beneficial reuse option. Materials and methods First, HP14 methodologies were applied on the studied sediments. These sediments had to be managed on shore according to French legislation. Then, following recommendations from a previous study, other ecotoxicological tests and modified ecotoxicological tests from HP14 methodology were selected. Ostracods mortality and growth tests were selected as a complement because its sensitivity to sediment ecotoxicity is known. To take into account the effects of extraction method and liquid/solid ratio on ecotoxicological impact of sediments, ecotoxicological tests have been applied to percolates. They have been obtained from up-flow percolation tests following the standard NF EN 14405. For each percolate, the rotifer clones reproduction test and the ostracod mortality and growth tests were performed. Results and discussion Contaminant analyses of sediments studied reveal differences in contamination between non-hazardous sediments. The majority of ecotoxicological tests carried out in the HP14 test batteries do not differentiate between non-hazardous sediments with low ecotoxicity. However, inhibition of rotifer reproduction and inhibition of plant germination and growth tests can be used. Among the complementary bioassays performed, the ostracods growth inhibition and multigenerational Daphnia reproduction inhibition tests are especially sensitive. Bioassays performed on percolates reveal low ecotoxicities that were not detected with conventional bioassays. For these tests, maximum ecotoxicities are observed on the first percolates for most of the tested sediments, and ecotoxicity effects decrease with the increase in the liquid/solid ratio. Conclusions The results enable us to propose a bioassay battery able to highlight the intrinsic toxicity of non-hazardous sediments. This is achieved through bioassays and using up-flow percolation columns to detect low ecotoxicity. This battery can be integrated into the SEDIMATERIAUX approach to ensure the choice of the beneficial reuse option for such sediment. As some of the proposed bioassays remain unsuitable for marine sediments, future studies will adapt the methodology to the presence of marine salts.