An extended quantitative weight of evidence with uncertainty evaluation for the risk assessment of dredged sediment

The sustainable management of dredged material requires robust risk characterization of contaminated sediment to protect both dredging areas and destination sites. However, integrated frameworks for assessing sediment quality prior to management are rarely applied. This study presents a paradigmatic case using a quantitative Weight of Evidence (WoE) approach on sediments from a canal in the Venice Lagoon (Italy), designated for future dredging. The aim is to assess whether integrating biological and chemical lines of evidence (LoEs) provides a more robust framework for dredged material risk assessment and management. Multiple LoEs were integrated, including chemical analyses of inorganic and organic contaminants, ecotoxicological bioassays, bioaccumulation tests, biomarker responses, and a novel transcriptomics LoE. Uncertainty in LoE integration was addressed probabilistically to quantify confidence in the final risk assessment. Results revealed a spatial gradient in sediment quality, with higher degradation near the industrial area. However, biological data indicated potential toxicity in sediments far from non-industrial sites that chemical analyses alone failed to detect. This discrepancy suggests the possible presence of not-targeted contaminants or other unknown factors, warranting further investigation. The study emphasizes the importance of assessing sediment effects across biological levels, tracing hazards to specific LoEs, and explicitly addressing uncertainty: these are three key steps for effective sediment risk assessment and informed decision-making.