158-12 19th and early 20th century mining altered the trace element geochemistry of Lake Superior’s sediment.

Session: Redox-Driven Nutrient and Contaminant Dynamics in Terrestrial Systems

Presenting Author:

Authors:

Abstract:

The Great Lakes comprise the largest freshwater watershed on Earth with about 21% of the world’s surface freshwater. The western watershed of Lake Superior witnessed significant mining activities during the 19^th and 20^th centuries. Northeastern Minnesota and Southern Ontario have a long history of copper and iron mining which may have led to increased presence of metals in nearby Lake Superior sediments. In this study, we collected a 30-cm sediment core off the west coast of the Isle Royale Island in Northern Lake Superior. Aliquots of sediment samples were fully digested using a combination of ultra-pure acids and inductively coupled plasma mass spectrometry (ICP-MS) was used to determine elemental concentrations. Enrichments of Cu, Fe, Mn, As, and Sb are above their natural backgrounds ranging from 2 times higher for Fe to 90 times higher for As, indicating a significant increase of mining-related metals in the sediments since the mid-1800s. Abandoned mines in the Thunder Bay region of Ontario north of the island may be the source of these metals. While mining is a likely source, other non-mining industrial activities, natural weathering and erosion of enriched parent rock, and diagenesis of deeper sediments could be potential sources as well. The mining activities that occurred during the 19^th century and early 20^th released significant amounts of trace metals in Lake Superior. As the need for critical metals is soaring, we recommend the implementation of sustainable mining techniques to minimize the impact on the Great Lakes and beyond.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-11219

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