RARE EARTH ELEMENTS IN HALIFAX HARBOUR SEDIMENTS - A TRACER OF PETROLEUM INPUTS?

Anomalies in rare earth element (REE) concentrations as indicators of petroleum or sewage inputs to marine sediments have been investigated using measurement of REEs in Halifax Harbour sediments. Concentrations of REEs increase from the outer to the inner more industrialized parts of the Harbour in concert with increasing organic carbon, aluminum and lithium content and decreasing grain size of the sediments. The increase is much greater for light than heavy REEs.

Light rare earth element enrichments are associated with elevated organic matter concentrations and inputs of sewage. No patterns of geographic association of elevated concentrations with specific point sources are obsserved. Depth variations in the enrichments in two sediment cores are indicative of increases in light REE inputs starting in approximately 1960, coincident with the beginning of substantial use of REEs in petroleum cracking catalysts. Correlations between the REE anomalies and silver concentrations in the sediment cores confirm the importance of the association of elevated light REE concentrations in the sediments with sewage.