Temporal and spatial variations of mercury, lead, zinc, and copper in sediments of the Saguenay fjord

Abstract

Sediment profiles of 19 cores from the Saguenay fjord, Québec, Canada, have been analyzed for mercury, lead, zinc, and copper. Core dating of post-1940 sediments is possible with above background concentrations of mercury. The results agree well with those obtained previously with 137Cs. The northern basin of the fjord is the site of a major accumulation of trace elements. The chronological distribution of mercury follows the events related to the operation of a chlor-alkali plant: construction, increased production, control of losses, and closing. The effect of a major landslide in 1971 is clearly shown in many sediment profiles. The western basin of the fjord contains sediments enriched in mercury, lead, and zinc. Mercury input in the fjord has diminished since 1970 but other trace element influxes keep increasing. Trace elements in the north basin correlate well with carbon. Atmospheric lead appears to be a major anthropogenic source in sediments of the western basin.