Environmental Impact of Submarine Rock Blasting and Dredging Operations in an Arctic Harbor Area: Dispersal and Bioavailability of Sediment-Associated Heavy Metals

摘要

In order to determine the possible impact on the marine environment, we present a study on the dispersal and bioavailability of sediment-associated heavy metals related to underwater blasting and dredging of bedrock operations during a quay construction. The environmental impact was primarily assessed by deploying a buoy setup including sediment traps, blue mussels, and passive samplers (diffusive gradient in thin films, DGTs) in a gradient from the construction site during the operations. Samplings were made during five separate periods covering a total span of about 2.5 months. Analyses included sedimentation rates, organic content, and metal concentrations of the material collected in the sediment traps and metal concentrations of the mussels and passive samplers. The construction work was associated with a considerable dispersion of sediments, organic material, and associated heavy metals. The major fraction of the sediment settled in the vicinity of the construction site. While the mussels were found to accumulate some metals in a distancerelated manner to the construction site and no such accumulation in the DGTs occurred, we conclude that most of the dispersed metals were particle associated. It was found that while a large part of the material settled in the vicinity of the construction site, most of the finegrained and/or organic sediment that was brought into suspension was transported further away from the construction site (beyond the 350 m) most likely carrying contaminants including heavy metals. For future studies of risks and monitoring of underwater blasting and dredging, we recommend to include a larger monitoring area and more importantly water samples of the suspended plumes.