Assessing the Potential Toxicity of Resuspended Sediment

Abstract

Two moderately contaminated freshwater sediments (Sorel Harbour, St. Lawrence River, Canada) were subjected to a suspension event. The objective was to assess the environmental impact of the disposal of dredged material in water, in particular, the short-term effects of dumping on the water column and the long-term effects of dredged sediment deposits. In a series of microcosms, the sediments were left to stand for 25 d under flow-through conditions (reference conditions). In a second series of microcosms, sediments were vigorously suspended for 15 min before being left to settle and were submitted to the same treatment as reference sediments during the following 25 d. Physicochemical and biological parameters (Daphnia magna and Hydra attenuata survival) were measured in overlying water throughout the experiment. Sediment toxicity was assessed with Chironomus tentans and Hyalella azteca exposed to sediments collected at both the beginning and end of the 25-d period. Pore-water toxicity was evaluated with D. magna. During the suspension process, in the Sorel Harbour mixed sediment overlying water, we observed effects on H. attenuata survival and ammonia and metals (chromium, copper, and zinc) releases. Meanwhile, in reference (nonmixed) and mixed sediments as well as in associated pore waters, there were no significant chemical modifications nor biological effects after the 25-d experiments. The developed approach, which attempts to simulate a dumping process, aims at allowing the assessment of the short-and long-term hazards resulting from a resuspension process in overlying water and in resettled sediments using both chemical and biological measurements.

Evaluation of metal contamination in sediments from north of Morocco: geochemical and statistical approaches

“…Knowledge of the extent of sediment contamination by metals in Tangier is important in case that government agency could plan to dredge bottom sediments. Dredging activities are known to release metals associated with sediments into the water column resulting in increase bioavailability and toxicity to aquatic organisms (Bonnet et al 2000;Bailey et al 2004;Bray 2008).…”

Effects of a physico-chemical treatment of a dredged sediment on its ecotoxicity after discharge in laboratory gravel pit microcosms

“…There are many studies on desorption of solid phase bound pollutants from sediments suspended in water ( [23][24][25][26][27][28][29][30]. A few studies focussed on the toxic effects of pollutants from sediment suspensions, most often in batch experiments where static conditions prevailed [8,[31][32][33].…”

“…Most sediments are simply stored on soils and exposed to rain precipitations, which generates a production of percolates with impacts on soil ecosystems, groundwater as well as surface aquatic ecosystems [5,6]. Other modes of disposal are sometimes used, such as disposal of dredged sediments in submerged gravel pits [7][8][9]. Important quantities of dredged sediments might also be valorized for the building of dikes and banks in rivers, canals and lakes.…”

Physicochemical and ecotoxicological evaluation of estuarine water quality during a dredging operation

“…Although we used short-term ecotoxicity endpoints, our results can be compared with other experimental designs carried out to assess the long-term effects caused by disposal of dredged material in water. Bonnet et al (2000) used D. magna and Hydra attenuata survival to assess the environmental impact of two moderately contaminated freshwater suspension sediments under flow-through conditions. After 96 h of exposure, the overlying water of one of the sediment samples showed ND not detected The results are the mean values and standard deviation of triplicate samples ND not detected some toxicity toward H. attenuata, which was probably due to the presence of ammonia and copper, whereas D. magna did not reveal any toxicity response.…”

“…Most of the information concerning the effects of contaminated sediments on estuarine organisms deals with the impacts of bed forming sediments. The ecotoxicological potential of dredged contaminated sediments is more difficult to assess and few studies have dealt specifically with resuspended contaminated sediments (Bonnet et al 2000).…”