Ecological Risk Assessment (ERA) of Open-water Disposal of Sediment to Support the Management of Dredging Project in the St. Lawrence River

摘要

The St. Lawrence River is subject to various anthropological pressures that can entail negative consequences for the ecosystem. As a result of the third and fourth St. Lawrence Action Plans, the current vision of sustainable management of this river and its main functions emphasizes the need for sound risk-based assessment approaches to support management decisions. More specifically, the sustainable navigation strategy, drawn up under St. Lawrence Action Plan Ⅲ, explicitly identifies the need to develop sediment quality assessment tools, including those derived from ecotoxicolog-ical studies. The first management option addressed in this perspective was the open-water disposal of dredged sediments. In this context, an ecotoxico-logical risk assessment (ERA) approach using chemical characterization in Tier 1 and benthic organisms' toxicity tests in Tier 2 was elaborated based on physicochemical, toxicity testing, and benthic community structure data acquired from sediment samples collected in 59 sites along the St. Lawrence River. Hence this ERA approach will be used to determine whether the risk posed by the exposure of benthic organisms to dredged sediments at deposit sites and downstream is acceptable and compatible with open-water disposal.