IMPACT OF SMALL CITIES ON TRACE METAL CONCENTRATIONS IN SEDIMENTS OF A RIVER DRAINING A PRIMARILY AGRICULTURAL AREA: WHITE RIVER (WEST FORK), INDIANA

Sediment and water samples were collected in 2008 and 2010 along the West Fork of the White River in east-central Indiana. Sample sites stretched along the river from its headwaters past the cities of Winchester, Muncie and Anderson (population ~5,000, ~65,000 and ~60,000, respectively) to study the impact of increasingly populated and more industrialized cities on a river that drains a predominantly agricultural area. Control samples were taken from non-urbanized tributaries, and comparison samples were taken from downstream of Indianapolis, Indiana’s largest urban area with a population of ~2 million. Field parameters such as pH and temperature were measured in situ. Water samples were analyzed for major ions and trace metals (e.g., Cd, Cr, Cu and Zn), and sediment extracts were analyzed for the same trace metals. Metal concentrations in sediments were very low in the headwaters, and increased between just over 1-fold to more than 6-fold as the river passes from Winchester (population ~5,000) through Anderson (population ~60,000). The increases vary between the metals; however, the overall impact of significantly larger Muncie is the same as the small town of Winchester (~2.7 increase), while the impact of similarly sized Anderson is twice as great than that of Muncie (~5 fold). We will evaluate the metal data with other indicators of urban and agricultural input (such as chemical markers Cl and NO₃), flow rates, and drainage areas. Our results indicate that even very small cities can irreversibly alter sediment compositions of rivers in mainly agricultural environments.