MERCURY AND OTHER TRACE METAL CONCENTRATION TRENDS IN WATER, SEDIMENT, AND BIOTA OF THE WABASH RIVER, INDIANA

The Wabash River in Indiana is the longest free-flowing river (661km) east of the Mississippi. Nonetheless, very few studies have focused on mercury (Hg) and other trace metals (e.g., Co, Ni, Cu) in this stream. Published research has focused mainly on the industrialized northern part of the State, near Chicago, and on the Ohio River valley at the southern end of the State. For rivers draining Indiana, including the Wabash River, numerous Hg-based fish advisories are posted; yet, very little to no data exist on the transport of Hg and trace metals in water or sediments. We present new Hg and trace metal data for the Wabash River as it flows through central Indiana. Water, surface sediment, and biota (i.e., insect and fish) samples were collected at various times between 2004 and 2007, from the river section that extends from upstream of Lafayette to Terre Haute. In contrast to the Wabash River upstream reaches, this section of the river has no water inputs from tributaries that drain reservoirs, and the above mentioned two cities, a few industrial activities and a power plant located upstream of Terre Haute are potential sources for metal- contamination of the river. Total-Hg concentrations determined on filtered water samples ranged from ~0.6 to 1.7ng/L during summer months, while in spring values reached up to 4ng/L. Total Hg levels in non-filtered summer samples ranged from ~1.6 to 5ng/L, with spring values up to 11ng/L. These values compare to those reported for rivers and streams in neighboring states. Dissolved trace metal concentrations are generally low (e.g., <2µg/L for Co, Ni, and Cu) and show only small increases as the Wabash River passes through Lafayette. We will present Hg and trace metal concentrations for biological tissues and compare those to aqueous and sedimentary levels as well as with trends/levels reported for other Midwestern rivers with similar land use types within their watersheds.