Niveau de contamination par le mercure des sédiments de surface et des crevettes du fjord du Saguenay

• Published in: Revue des sciences de l'eau
• Main Authors: C. Rouleau, E. Pelletier, G. Canuel
• Format: Article in Journal/Newspaper
• Language: French
• Published: Université du Québec - INRS-Eau, Terre et Environnement (INRS-ETE) 2005
• Subjects: Sciences Humaines et Sociales; Social Sciences and Humanities; Mercure; crevettes; sédiment; Saguenay; bioessais; Mercury; shrimps; bioassay; envir; geo; Pandalus borealis
• Online Access: http://www.erudit.org/fr/revues/rseau/1989-v2-n1-rseau3253/705021ar.pdf; https://www.erudit.org/fr/revues/rseau/1989-v2-n1-rseau3253/705021ar.pdf; https://doi.org/10.7202/705021ar; https://id.erudit.org/iderudit/705021ar; https://www.erudit.org/fr/revues/rseau/1989-v2-n1-rseau3253/705021ar/; https://core.ac.uk/display/59609283; https://academic.microsoft.com/#/detail/1694554586

From 1947 to 1976, many tons of industrial mercury were tipped into the Saguenay River and a large amount of this toxic heavy metal is now in the sediments of the Saguenay Fjord. Surface sediments (0-2 cm) were collected at seventeen stations along the inner basin of the Saguenay Fjord and analysed for total mercury content. About 150 shrimps (Pandalus borealis) fished in the Sainte-Rose-du-Nord area were also used for mercury analyses and the determination of mercury uptake rate from contaminated food. The mercury concentrations in surface sediments ranged from 0.18 to 0.20 µg.g-1 (dry weight) with a mean value of 0.63 µg.g-1. This mean level is about one order of magnitude higher than the background level found in deep sediments. The examination of available data for surface sediments in the Sainte-Rose-du-Nord vicinity, located in the first half of the inner basin, shows the "steady state" of the mercury contamination over the last 10 years. Indeed, the mercury concentrations observed in surface sediments ranged from 0.75 to 1.20 µg.g-1, with a mean value of 0.93 µg.g-1 since 1976. The steady state of mercury contamination can be explained by two hypothesis : (1) an unexpected highly active bioturbation mechanism contributes to the mercury remobilisation from lower sediment layers (10-20 cm) and its vertical transportation up to the surface, or (2) the anthropogenic upstream discharge of mercury was not really stopped in 1976 and one or many unidentified sources are still active along the Saguenay River. The mercury concentrations in the edible part of shrimps (fished in November 1985) ranged from 0.13 to 0.58 µg.g-l (wet weight) with an average value of 0.36 ± 0.11 µg.g-1. A positive and significative linear relationship (r = 0.786) is observed between the Hg concentration in the edible part and the total wet weight of the shrimp. The mean Hg in the edible part found in 1985 is not significantly different from the mean value reported in 1932. The mean concentration found in the cephalothorax and the cuticle ...