Geochemical tracing of lead isotope ratios and metal concentrations across space and time using biomonitors

Anthropogenic metal emissions have increased alongside population growth, urbanization, and industrial development, altering geochemical signatures across natural systems. There is a growing need for monitoring frameworks capable of establishing robust baselines and detecting spatiotemporal shifts in contaminant distributions. Biomonitoring, the use of organisms or their byproducts to quantify environmental conditions, provides an integrative approach to assessing geochemistry. This thesis applied biomonitoring across multiple spatial and temporal scales, using elemental concentrations and Pb isotope ratios as tracers to assess variability in environmental metal impacts across three unique systems. The first study examined geochemical variation across urban, suburban, and rural environments by analyzing honey collected during the COVID-19 lockdown period. This time of reduced human activity provided a unique opportunity to evaluate spatiotemporal changes in atmospheric metal composition associated with declines in emissions from traffic, shipping, manufacturing, and public transit. Honey samples from Vancouver and Brussels—cities with contrasting population densities, urban structures, and legacies of metal use—were compared to assess the sensitivity of honey as a biomonitor of atmospheric metals. The second long-range spatial study investigated trans-Pacific trends in metal concentrations and Pb isotope ratios using chum salmon (Oncorhynchus keta) and Pacific herring (Clupea pallasii) from Canada and Japan. The broad migratory range of chum salmon enabled comparison of basin-scale geochemical signatures across the sub-Arctic North Pacific Ocean, while Pacific herring from Japanese coastal waters provided a regional reference for western sub-Arctic North Pacific metal inputs, revealing the impact of Asian metal emissions. The final study examined long-term environmental trends archived in bowhead whale (Balaena mysticetus) baleen from the Hudson Bay. Because baleen grows continuously, it preserves sequential records of elemental incorporation, capturing up to two decades of environmental variability, resolving spatiotemporal shifts in metal exposure and exposing the seasonal impact of increased shipping throughout the study period. Collectively, these biomonitoring systems demonstrate how elemental concentrations and Pb isotope ratios can be used to answer different geochemical questions across spatial and temporal scales. This thesis demonstrates the power of biomonitoring as a framework for tracking anthropogenic metal emissions through time and space, capable of capturing fine-scale and larger geochemical trends.