The history of metals contamination in the Great Salt Lake, Utah revealed through a paleolimnological analysis
Wayne Wurtsbaugh, Utah State University, Logan, Utah, USA
Peter Leavitt, University of Regina, Regina, Saskatchewan, Canada
Katrina Moser, University of Western Ontario, London, Ontario, Canada
Multiple sediment cores were used to address how metals contamination has changed over the last 200 years in the Great Salt Lake. The cores from Gilbert and Farmington Bay were sectioned in 0.5- cm intervals, and analyzed for over 20 different metals. Metal concentrations in the cores from Gilbert Bay showed increases that paralleled the known production of the specific metals in Utah. For example, lead in the sediments increased 20 to 40-fold above background levels (pre-1850) and peaked from 1930-1950, coincident with the years of highest production of lead by smelters. Mercury also increased, but “only” 4-12 times above background. However, since the 1950s, concentrations of most metals have declined to 20-40% of the peak levels as a consequence of decreased mining (e.g. lead and zinc), or cleaner smelting technologies (e.g. copper).
Consequently, the paleolimnological record indicates that most of the high metal concentrations in the lake are a legacy effect of unregulated smelting practices in the 20th century. However, arsenic and selenium concentrations in the sediments are either stable or increasing, suggesting that significant loading is continuing to the lake. Despite the decreasing concentrations for many metals, levels of selenium, copper, arsenic, mercury, cadmium, lead and zinc in the surficial sediments are still above Threshold Effect Concentrations that have been established for freshwater organisms, suggesting that we still need to be concerned with the metals in the lake sediments.