URBAN LAND USE TYPES AND THEIR EFFECTS ON LOW ORDER STREAM CHEMISTRY, COLUMBUS, OHIO

The influence of urban land use on water quality in areas of high population density can be significant. Particular urban land use types each contribute their own suite of chemical constituents. Previous studies on the urban impacts to streams have primarily examined the bulk chemical contributions to higher order rivers and streams, while not focusing as strongly on the tributaries that control their chemistry. Small scale analysis of elemental fluxes in urban tributaries is necessary in order to better understand the influence of urban land use types on stream chemistry because many of the sources of chemical constituents are thought to be non-point sources. The present study focuses on a series of tributaries to the Olentangy River in Columbus, Ohio that represent the lowest order streams and their contributions to the chemical makeup of the river. The waters of these tributaries were analyzed for major ions, nutrients, dissolved organic carbon (DOC) and trace metals. Major ion concentrations for some elements were noticeably higher than typical natural waters with F concentrations ranging from 10.3 to 26.4µM, Cl from 1675 to 4400µM, and SO₄ from 1945 to 5922µM. Nutrient concentrations such as NO_3, NH₄, and PO₄ varied from 20.3 to 220µM, 1.11 to 3.74µM, and 0.11 to 4.58µM respectively. Total N/P ratios varied from 2.13 to 8.62 throughout the various urban land use types sampled. DOC concentrations range from 2.0 to 5.1 mg C/L and conform to similar size streams at baseflow conditions. Trace metal concentrations for V and Cu ranged from 0.73 to 4.25µg/L and 1.28 to 4.54µg/L respectively with unfiltered samples typically yielding higher concentrations than filtered ones. All measurements to date have been taken at or near baseflow conditions and work in the immediate future will be focused on measuring stream discharge to determine elemental fluxes, analysis of tributary chemistry post storm runoff, and analysis during a storm event to examine concentrations through time. Additional trace metals including Mo, Cr, Ni, Pb, Zn, and Pt will be included in future analyses.