An integrated chemical and biological study of the bioavailability of metals in sediments from two contaminated harbours in New Brunswick, Canada

Abstract

Dalhousie and Belledune, New Brunswick, Harbour sediments are known to be contaminated with copper, zinc, lead and cadmium. Relatively high concentrations of these metals in the resident organisms were reported from previous surveys. Experiments were conducted in the laboratory to study the partitioning and bioavailability of heavy metals present in the contaminated sediments. A procedure to extract metals sequentially from sediments was used to determine their distribution in various geochemical fractions. A companion experiment was also set up to determine the bioavailability of trace metals from these sediments. Experimental data indicated that the metals associated with hydrous oxides of iron and manganese and the residual fraction carried the major burden of heavy metals in the sediment. Appreciable uptake of metals was observed to occur only from the Belledune sediment. Biota accumulated lead and cadmium to the greatest extent, with strontium, cobalt and zinc taken up to a lesser degree as compared with control animals in uncontaminated sediments. Concern is directed to heavy metals associated with hydrous oxides of iron and managenese because changing environmental conditions can transfer these elements from the sediments into the aqueous phase.