GEOCHEMICAL CHARACTERIZATION OF STREAM SEDIMENTS FROM A HISTORICALLY CONTAMINATED SITE

Two streams flowing through the Oronogo Duenweg Mining Belt Superfund site (ODS) of southwestern Missouri were studied. Turkey Creek and Center Creek are major contributors of metals to downstream reservoirs. ODS was designated a Superfund site in 1990 and presently is 90% remediated. Sediment samples were collected along a 10 km segment in each stream and their metal content, potentially bioavailable fraction, and toxicity determined. Metals were first extracted using an acidic solution (aqua regia for total metal content, 0.11 M acetic acid for potentially bioavailable fraction) and then analyzed using an ICP-MS. Zinc and lead median concentrations in sediments were 19 and 52 times the background. The potentially bioavailable fraction varied from 0.19% (Pb, Center Creek) to 12.5% (Zn, Turkey Creek), and toxicity (estimated by ΣPEC-Q_Cd,Pb,Zn) was high in 40% of the samples in Turkey Creek and 78.5% of the samples in Center Creek. While this level of toxicity would likely affect aquatic organisms, the limited mobility of both primary (sulfides) and their secondary minerals suggests a lesser threat to humans.