Isotopic evidence for naturally occurring sulfate pollution of ponds in the Kankakee River Basin, Illinois-Indiana

Ecosystem restoration surveys across the Kankakee River Basin indicate that ponds in riparian zones contain elevated sulfate concentrations. The sources of high sulfate in many ponds were investigated by sampling ground waters, precipitation, and applied fertilizers in the Kankakee and Iroquois subwatersheds of the basin. The S-34(SO4) and O-18(SO4), analyses discriminated among possible regional anthropogenic and natural sources. Some sulfate-bearing fertilizers may have contributed to elevated SO42- in ponds but there is isotopic evidence suggesting that pyritic glaciofluvial sediments in the surficial aquifer may be the source of larger SO42- concentrations in ponds, An isotopic analysis of one SO42--H2O system in a riparian zone revealed that FeS2 oxidation reactions are possible processes leading to local sulfate pollution in riverine ponds.