Geochemistry and environmental implications of the surficial sediments in northern Placentia Bay, Newfoundland

Abstract

Three chemically distinct sediment types, as defined by factor analysis, occur in northern Placentia Bay; these correspond to the muds, the sands, and the amodal sediments (tills) in this area. Factors that control the sediment geochemistry in Placentia Bay are: the organic-rich fraction, the clay-size fraction, the calcium carbonate fraction, the iron-containing fraction, the non-clay-size aluminous minerals, and the silica-rich fraction. The relative importance of these factors in controlling sediment chemistry is different in each sediment type. The trace metal concentrations and associations are also different in the three sediment types.The weak acid leachable fractions of the metals investigated are derived primarily from the organic material, the clay-size fraction, and the calcium carbonate, even in the sands where these three fractions are only a small part of the sediment. The non-leachable fractions of the metals are controlled by the organic material and by minerals such as feldspars and micas.The average concentrations of the major components and of the trace metals, and the factors that control these concentrations, are not significantly different in Long Harbour sediments (after five years of operation of the phosphorous plant there) compared with similar sediments in Placentia Bay. The association of Pb in Long Harbour sediments may be different than in other areas.