Distribution and partition of cobalt, nickel, chromium, and vanadium in the sediments of the Saguenay fjord

Abstract

In the Saguenay fjord sediments, cobalt (Co) concentrations vary between 5 and 20 ppm, nickel (Ni) concentrations between 7 and 36 ppm, chromium (Cr) concentrations from 33 to 70 ppm, and vanadium (V) concentrations from 67 to 149 ppm in relation to texture and location. The highest concentrations are found in the fine-grained sediments from the upper part of the fjord and the lowest concentrations occur in the sandy sediments near the mouth of the fjord. On the average, the fjord's muds are neither greatly enriched nor depleted in Co, Ni, Cr, and V when compared to muds from the St. Lawrence estuary and the open Gulf of St. Lawrence.Acetic acid extractions indicate that 8 to 25% of the total Co, 11 to 29% of the total Ni, 2 to 9% of the total Cr, and 5 to 23% of the total V are contributed by the non-detrital fraction and may be available to the biota in the fjord. Non-detrital Co, Ni, Cr, and V appear to have been removed from solution by adsorption onto fine-grained inorganic particles and their distribution controlled by the sedimentation pattern. Non-delrital Cr, V, and Ni are also associated with Mn and Fe oxides, which are present as grain coatings. Most of the Co, Ni, Cr, and V in the detrital fraction, which accounts for 71 to 98% of the total elemental concentrations are found in sulphide, oxide, and ferromagnesian minerals. These minerals accumulate at the same rate as other detrital sedimentary material in response to the present depositional conditions.The discharge of industrial waste has not resulted in an increase in the concentrations of Co, Ni, Cr, and V in the sediments above their natural levels.