PARENT SESSION
Poster Session # 4: Paleoecology.

Monday, August 4 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Industrial development on the American Bottoms -- a test of stable isotope analysis in paleolimnology.

Vermillion, Brian¹, Bala, Indu¹, Retzlaff, William¹, Brugam, Richard^*,1, ¹ Southern Illinois University Edwardsville, Edwardsville, IL, USA

ABSTRACT- Many investigators have shown that lakes in industrial areas contain sediment records of past pollution. Techniques of stable isotope analysis have only recently been applied to the interpretation of these records. We compared the stable isotope record with pollen, diatom, and chemical analysis of sediment. We studied Horseshoe Lake on the American Bottoms, a floodplain of the Mississippi River east of St. Louis, MO. Horseshoe Lake is an oxbow lake located in Granite City, IL, a town with two Superfund sites and an integrated steel mill. Fifteen sediment cores and 84 surface sediment samples have been collected from Horseshoe Lake. Five of these cores were dated using pollen analysis and ²¹⁰Pb. Diatom analysis shows that in pre-settlement times the lake was clear and shallow with lots of macrophytes. The modern lake is very eutrophic. In the late 1930's and 40's, Pb, Zn, and Cd sediment concentrations increased. The isotopic composition of the Pb indicates that it originates from industrial contamination. During the 1920's, Si, Al, and Ti (elements indicative of erosion) decrease as Ca increases in concentration. An increase in ¹⁵N above 10 ^o/_oo during the 1920's also indicates contamination of the lake by sewage or animal waste. We hypothesize that the increase in Ca results from increased deposition of CaCO₃ resulting from the eutrophication of Horseshoe Lake by sewage inputs.

Key words: stable isotopes, heavy metals, paleolimnology, environmental contamination