Titanium and tungsten in highway runoff at Pullman, Washington

Abstract

The inputs of titanium and tungsten to a 0.6 acre (2323 m2) road surface area were investigated. The selection of a viaduct at Pullman, Washington as a study area permitted the exclusion of metal input from sources other than the road surface. Dustfall and precipitation were sampled at the viaduct and at a control station. Titanium and tungsten were not detected in precipitation samples at levels of 1.0 and 15 mg/1 in the diluted sample digests, respectively. Tungsten was also not detected in dust samples. Average deposition rates for titanium in dust were found to be 43.6 mg/m2/day at the viaduct stations and 44.3 mg/m2/day at the control station. Road runoff was collected and flow was measured during three storm events. Rainfall intensity and traffic density were also monitored. The mean concentration of titanium in the road runoff was 12.7 mg/1 while tungsten varied from non‐detectable (2.5 mg/1) to 25 mg/1. A mathematical model was developed allowing estimation of metal loadings for a typical storm event utilizing data on the total runoff volume.