Date of Graduation

Spring 2017

Degree

Master of Science in Geospatial Sciences

Department

Geography, Geology, and Planning

Committee Chair

Robert Pavlowsky

Abstract

Tailings releases associated with large-scale historical Pb mining in St. Francois County, Missouri resulted in system-wide contamination of Pb and excess sediment in the Big River. Previous studies have addressed basin and segment scale variability of the contaminants; however, little is known about reach and bar scale variability. This study addresses how mining sediment inputs influence bar form and geochemistry across a range of scales. Bar sediment samples were collected at 21 reaches and analyzed for particle size and geochemistry, while air photo analysis was used to evaluate channel morphology, bar type, and area. Bar area is initially low in the upper mining region but increases with distance downstream. Bars near mining inputs are highly contaminated with Pb and decrease in contamination with distance downstream. While chat-sized mining sediment has not moved more than 60 km downstream, having attenuated or dispersed locally by moving into storage in bars or young floodplains, Pb contamination is transported further with fine sediment and is found throughout the study area. Bar sediments are well-mixed vertically; the bar head contains more Pb than the tail near mining sites. Signs of geomorphic recovery indicate that the channel is in the process of returning to equilibrium; however geochemical recovery will likely not occur for centuries. Further, if increasing trends in flooding continue, bar formation and mobility may increase in the future.

Keywords

fluvial geomorphology, Missouri, lead, mining, sediment transport

Subject Categories

Environmental Chemistry | Hydrology | Sedimentology

Copyright

© Lindsay Marie Olson

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Open Access

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