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Journal of Geophysical Research

Heavy metal sedimentation in Saanich Inlet measured with 210Pb technique

Authors

  • E. Matsumoto,

  • C. S. Wong


Abstract

Two undisturbed sediment cores at 220 and 200 m in the deepest basin of Saanich Inlet, British Columbia, were collected by a box corer. In the upper 30 cm the sediment porosity exhibited an abrupt decrease with depth due to compaction. The corrected depth of sediments without compaction was calculated. The 210Pb profiles were plotted against the corrected depth in order to determine the accumulation rate at the surface in cm yr−1. The sedimentation rate in g cm−2 yr−1 was calculated from the accumulation rate. A sedimentation rate of 0.093 g cm−2 yr−1 was obtained at the end of the deep basin away from the sill entrance and 0.27 g cm−2 yr−1 near the sill of the deep basin. The Pb, Cu, Cd, and Hg contents in the sediment cores appeared to decrease with depth. A present metal flux of 1.9–5.1 dpm cm−2 yr−1 was inferred for 210Pb, 3.6–11 μg cm−2 yr−1 for stable Pb, 6.3–14 for Cu, 0.11–0.48 for Cd, and 0.029–0.072 for Hg. When some recent measurements of heavy metal concentrations in the seawater near the sill of the deep basin of Saanich Inlet were used, a residence time in the water column of 0.08 years was inferred for 210Pb, 0.07 for stable Pb, 0.3 for Cu, 3 for Cd, and 2 for Hg.

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