STRONTIUM ISOTOPIC RATIOS OF SURFACE WATERS IN THE HISTORIC TRI-STATE MINING DISTRICT AS AN IDENTIFIER OF SOURCES, WATER MIXING, AND CONTAMINATION

The mining of lead and zinc ores in the Tri-State mining district of Kansas, Missouri and Oklahoma resulted in some of the most severe environmental degradation in the country and produced large amounts of waste rock, known as ‘chat’, left in surface piles around the mines. These chat piles, located mostly in Oklahoma near the town of Picher, contain potentially harmful elements that can be leached from the rock into local streams and sediment. The purpose of this investigation is to analyze the impact of the Picher mine tailings on local streams, evaluate the extent of contamination relative to the distance from exposed chat piles, and assess if strontium isotopic ratios (⁸⁷Sr/⁸⁶Sr) of surface waters can be used for source identification and water mixing.

Results show water samples collected upstream and/or greater than 15 km downstream from the center of mining activity had lower concentrations of cations, anions, and metals relative to four sites located within 15 km downstream from the center of mining activity. This pattern persisted for concentrations of contaminants such as Zn, Mn, Fe, Co, Ni, As, Se, and Cd. The Criterion Continuous Concentration (CCC) for zinc in freshwater is 0.120 mg/L, which was exceeded by all four sites within 15 km downstream from the center of mining activity (up to 2.87 mg/L). Results show elevated concentrations of Se, As, Ni, Zn, Al and other environmentally harmful elements in water relative to local chat pile density. Surface waters of Tar and Lytle Creeks, which drain the Picher Mining District, have strontium isotopic ratios between 0.71259 and 0.71519, while the Spring River (0.71118, 0.71137) and Neosho River (0.70960) display different isotopic signatures. There is an isotopic shift towards more radiogenic strontium values in the downstream Neosho River (0.71005) after it has converged with the Spring River and Tar Creek. The strontium isotopes were used to determine mixing of the rivers and mining water discharge within the region.