LEAD, IRON, CHROMIUM AND ZINC IN ROAD RUNOFF AT PULLMAN, WASHINGTON

The inputs of iron, lead, chromium and zinc to a 0.6 acre road surface were investigated. The selection of a viaduct in Pullman, Washington as a study area permitted the exclusion of metal input from non-road surfaces. Dust and precipitation metal deposition rates were measured at the viaduct as well as at a control location. It was found that the primary source of metals at the road surface was the operation of motor vehicles. For three separate storm events, runoff samples were collected, flow was measured and runoff samples were analyzed for total solids, total metals and dissolved-colloidal metals. Less than 5 percent of each metal in the runoff samples existed in the dissolved-colloidal fraction. Mean concentrations of total metals in road runoff were 1.86, 89, 0.139 and 19.1 mg/l for Pb, Fe, Cr, and Zn, respectively. A mathematical model was developed allowing the estimation of metal loadings for a storm event typical of the area, given the total runoff volume for the particular storm event. It was also found that a residual amount of metals remains on the road surface after each storm. © 1979.