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UBC Theses and Dissertations

Evaluation of trace metal distributions (arsenic, cadmium, lead) and lead sources in sediments from a sound and an inlet on the west coast of Vancouver Island, British Columbia Ikehata, Mariko


Barkley Sound and Alberni Inlet, located on the west coast of Vancouver Island, British Columbia, are home to economically important oyster farms. The headwaters of Alberni Inlet are proximal to the city of Port Alberni, where industrial activities (e.g., paper mills, recycling plants) release significant quantities of heavy metals into Alberni Inlet annually. The distribution of As, Cd, and Pb and Pb isotopic composition of Pb were studied in surface and cored sediments collected downstream from the paper mill using quadrupole and multi collector inductively coupled plasma mass spectroscopy (Q-ICP-MS, MC-ICP-MS). Surface and core sediment concentrations of As, Cd and Pb generally decrease downstream from Port Alberni, with the exception of a Pb spike observed in Barkley Sound. Alberni Inlet and Barkley Sound display ranges of 3.8-24 and 3.5-21.6 ppm for As, from 0.03-0.87 and 0.2-1.1 ppm for Cd, and 4.1-18 and 2.9-24.2 ppm for Pb, respectively. Scavenging of dissolved metals is observed at the distance of 10-25 km downstream from Port Alberni. Based on comparison to Sediment Quality Guidelines, the environmental impact of trace metals in the sediment on bottom dwelling organism is low. Major elements compositions determined using Aluminum as an elemental normalizer indicated that the sediment corresponds to a source predominantly from Vancouver Island bedrock. The isotopic composition for surface sediment ranges from 1.17020 to 1.21602 for ²⁰⁶Pb/²⁰⁷Pb, and 2.0397 to 2.0835 for ²⁰⁸Pb/²⁰⁶Pb. In core samples, the range is from 1.16571 to 1.19109 for ²⁰⁶Pb/²⁰⁷Pb and 2.06883 to 2.08533 for ²⁰⁸Pb/²⁰⁶Pb. Lead isotope fingerprinting indicates that sediments derived from Vancouver Island were contaminated with trace metals by a source displaying the Pb isotopic signature of the Sullivan Ore, the primary anthropogenic Pb source for British Columbia. This is consistent with paper mill effluent from Port Alberni. Sediments from the lower inlet and Barkley Sound also show a contribution from Chinese loess. Other human activities are most likely responsible for the spike in Pb concentrations in Barkley Sound. This study demonstrates that the combination of trace metal analysis and high precision Pb isotopic data are effective tools for monitoring anthropogenic input into the environment.

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