ASSESSMENT OF HEAVY METAL AND PAH CONTAMINATION OF URBAN STREAMBED SEDIMENTS ON MACROINVERTEBRATES GARY BEASLEY and PAULINE E. KNEALE ∗ School of Geography, University of Leeds, Leeds LS2 9JT, U.K. ( ∗ author for correspondence, e-mail: p.e.kneale@leeds.ac.uk; phone: 0113 343 3340; fax: 0113 3433308) (Received 20 August 2002; accepted 12 April 2003) Abstract. The results from measuring PAH and metal contamination together with macroinverteb- rate communities at 62 headwater stream sites gives a significant insight into the range and scale of contamination. Monitoring streambed sediments at 62 sites from rural to inner city and in industrial locations presented a unique opportunity to distinguish the conditions that enhance pollution runoff at sites that are less obviously ‘at risk’ and to compare these results with sites of expected high contamination, for example in industrial areas and at motorway junctions. We used pCCA (partial Canonical Correspondence Analysis) to tease out the relationships between individual macroinver- tebrate families and specific metal and PAH contaminants, and showed that it is not always the metals and PAHs with the greatest total concentrations that are doing the damage to the ecology. Ni and Zn are the critical metals, while benzo(b)fluoranthene, anthracene and fluoranthene are the most contaminating PAHs. The results identify previously unrecognized ‘high risk’ pollution sources, lay byes used for commercial parking, on-street residential parking areas, and the junctions at the bottom of hills with traffic lights, where surface runoff feeds rapidly to the streams. While this study looks at sites across Yorkshire, UK, it clearly has a broader significance for understanding contamination risks from diffuse runoff as a prerequisite for effective sustainable urban drainage system (SUDS) agendas and the protection of urban stream ecology. Keywords: diffuse urban runoff, macroinvertebrates, metal contamination, PAHs, stream bed sedi- ments 1. Introduction Despite efforts to control water quality through targeting point sources of major contaminants, many rivers and streams experience biological quality below that suggested by their environmental characteristics. Streambed sediments can be ex- pected to accumulate have metal- and oil-based contamination (polycyclic aromatic hydrocarbons, PAHs) in urban areas where runoff is associated with vehicle traf- ficking, pavements, roofs, guttering and industry (Marsalek et al., 1999; van Metre et al., 2000). Metals and oils preferentially attach to fine particles (Estèbe et al., 1997; Lee et al., 1997), which are entrained in surface runoff and deposited as stre- ambed sediments. The sediment contamination is often a magnitude greater than in the overlying water column (Power and Chapman, 1992). These contaminants exert a persistent and wide-reaching stress on the freshwater ecosystem leading to Water, Air, and Soil Pollution: Focus 4: 563–578, 2004. © 2004 Kluwer Academic Publishers. Printed in the Netherlands.