Date of Graduation

Summer 2022

Degree

Master of Science in Geospatial Sciences

Department

Geography, Geology, and Planning

Committee Chair

Robert Pavlowsky

Abstract

In St. François County, Missouri, compromised above-ground tailings piles and containment ponds from historical mining activities in the Old Lead Belt released considerable amounts of dolomitic, Pb- and Zn-contaminated waste sediments to the Big River, contributing to significant downstream floodplain and channel sediment contamination. Previous studies have documented the effects of heavy metals on Big River biota and water quality, as well as benthic habitat disruption resulting from the influx of small sediments. Few have considered the effects and future contamination risk of the coarse waste sediments (2-16 mm in diameter), locally called “chat”, which retain high Pb and Zn concentrations and can constitute over 40% of the1) quantify the percentage of dolomite tailings in downstream channel bar deposits, 2) determine the downstream extent of chat transport from mine waste input sources, 3) evaluate the fine sediment Ca, Pb, and Zn concentrations and their relationship to mine waste, and 4) evaluate the future contamination potential of coarse chat in bar deposits in the Big River. The study showed an overall increase in the average percentage of 2-16 mm sized sediments within bar deposits below mine locations which decreased with distance downstream. Within the study area, dolomite tailings percentages in bar sediments80% in 2-4 mm, 65% in 4-8 mm and 20% in 8-16 mm size fractions. The percentage of dolomite dropped to 5% for 2-16mm sediments around 40 km below Flat River Creek while the10% as far as Washington State Park (50 km downstream from Flat River). Heavy metal concentrations peaked just above Flat River with8,700 mg/kg and almost 12,000 mg/kg for Zn. Pb and Zn concentrations decreased with distance downstream but remained above PEC toxic levels throughout the study area. Transport rates between 350 m/yr for 2-4 mm and 175 m/yr for 8-16 mm sediments indicate high residence times within the channel for these sediments. Further, coarse tailings contain high Pb concentrations which may be released to the aquatic environment by geochemical weathering and abrasion due to reworking and transport during flood events.

Keywords

Mine waste; Pb and Zn contamination; chat; coarse tailings; channel bar deposits; Big River, MO; Old Lead Belt, MO

Subject Categories

Environmental Indicators and Impact Assessment | Geochemistry | Geology | Geomorphology | Natural Resources and Conservation

Copyright

© Jennifer Pace Witt

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