Challenges and strategies for dredged sediment decision management in Venice lagoon (Italy)

This study presents the results of extensive sediment characterization campaigns conducted in 2024-2025 on more than 400 sediment cores collected across the Venice Lagoon, yielding approximately 1400 samples analyzed for chemical contamination and ecotoxicity. Investigated sediments presented exceedances of the protective screening values defined by the Italian legislation for metals (in particular Cd, Hg and Zn) and for HCB, PCDD/F and PCB; embryotoxicity test (P. lividus) showed a more widespread and extensive toxicity than the bioassays evaluating effects on bioluminescence (A. fischeri) and on algal growth (P. tricornutum) and represented therefore the main driver in the overall sediment classification. The dataset was used to test and calibrate the new classification tools recently set (2023) by the Italian legislation to regulate dredged sediment management in the Venice lagoon, with the aims of i) improving the balance between chemical and ecotoxicological evidence, through calibration of the ecotoxicological index for the lagoon context, ii) deriving alternative threshold values, specifically set for the Venice lagoon on the basis of the new dataset, and iii) identifying refinements and possible changes to criteria set by legislation for the integration of chemical and ecotoxicological results and sediment classification. Overall results are meant to support the appropriate reuse of dredged sediment for morphological restoration while optimizing the costs and resources in dredging operations.