THE CHEMICAL-COMPOSITION OF HIGHWAY DRAINAGE WATERS .1. MAJOR IONS AND SELECTED TRACE-METALS

Measurements of volumetric discharge and concentrations of dissolved ( less than 0. 45 mu m) and particulate ( greater than 0. 45 mu m) major ion and trace metal components of road drainage water have been made during ten storm events at a motorway site in northwest England. With the exception of K** plus and Mg**2** plus , which were often significantly associated with the particulate fraction, the major ion constituents were predominantly in the dissolved fraction. Of the trace metals, Pb and Fe were largely particle-associated, Mn was predominantly dissolved, and Cu and Cd exhibited intermediate behaviour. A 'first flush' effect is seen for the dissolved components, but the particle-associated elements show a much more complex temporal variation related to storm intensity and flushing.