Impact of road run-off on receiving streams in eastern England

Invertebrate samples from nine East Anglian rivers were collected above and below crossings of the A12 and A14 trunk roads in spring and summer 1996 to assess any impact due to road run-off discharges. The Biological Monitoring Working Party (BMWP) score, average score per taxon (ASPT) and Shannon diversity index values were compared between upstream and downstream sites. Only the BMWP score was significantly lower in summer at downstream sites in those rivers crossed by the A12. Zinc, lead and cadmium concentrations in sediments and invertebrates (Asellus aquaticus, Gammarus pulex, Sialis lutaria) did not differ significantly between upstream and downstream sites. There was a significant relationship between metal concentrations in sediments and invertebrates only for lead. Road run-off from these trunk roads appears to have no major impact on the receiving streams.