PREDICTING CONTAMINANT EXPOSURE FROM DREDGING OPERATIONS

摘要

Understanding the environmental risk of dredging operations requires modeling of contaminant release, fate and transport to perform exposure assessments. Contaminant releases occur from dredging, losses from the new sediment face and residuals, and dredged material disposal. The USACE ERDC has developed a suite of models in its Automated Dredging and Disposal Alternatives Modeling System (ADDAMS) and Surface-water Modeling System (SMS) to predict contaminant release, fate and transport.Currently, ERDC is developing enhanced contaminant fate and transport features in its sediment-water interaction model (CAP/RECOVERY) to model reactive capping media, contaminant degradation, sediment bed consolidation and groundwater advection and in its Particle Tracking Model (PTM) to model contaminant/resuspended solids/water column interactions on local time and spatial scales. A module of the fate and effects of contaminants for PTM has been developed based on compatible formulations for non-conservative substances. The contaminant module incorporates basic water quality processes/kinetics, including adsorption/desorption, decay, and volatilization, as well as settling, deposition, and resuspension. Partitioning of contaminants to dissolved organic carbon and multiple particle types is being considered. Organic toxics degradation will be based on the SEAM3D model of sequential electron acceptance. Future developments will couple the CAP/RECOVERY and PTM models with ICM, a basin scale resource management tool, which will include living resources, submerged aquatic vegetation, and diagenesis to model contaminant cycling between the sediment bed and water column for prediction of long-term risk. Uncertainty methods and tools will be incorporated in the models to aid risk assessment.