First flush effect of metals and anions in stormwater runoff from roads in mid-Sweden

This paper investigates the first flush effect of metal and anions in stormwater runoff from a highway and local urban road in Sweden. The study was conducted after a dry three-day period. The results showed that 50-60% of the total mass of Zn, Cu, Pb, Ni, Co, Cd and as was transported in the first 30% of the runoff. At the end of the highway site, CU first flush concentrations exceeded the target values for small watercourses by a factor of 3. The runoff concentrations at the local urban road site were considerably higher, but might have been affected by the road materials, the rain intensity, and by vehicles stopping at the traffic lights. The study concluded that the first flush effect from a single rain event can cause high concentrations of Cu and Pb that may be toxic to biota.