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(PM138) Characterising impacts upon receiving waters of contaminated suspended solids derived from highway runoff: Field survey.

Gaskell, P 1, Wood, R1, Lingard, D1, Guymer, I1, Maltby, L1, 1 The University of Sheffield, Sheffield, South Yorkshire, UK

ABSTRACT- Runoff from highways has the potential to cause considerable impact on freshwater communities and current methods for assessing the impact of highway runoff on UK rivers and streams are not sufficient to meet the needs of the EU Water Framework Directive. The objective of the current project is to assess the ecological impact of contaminated solids in highway runoff by: a) determining the fate in watercourses of suspended solids discharged from operational highways; b) understanding and quantifying the processes involved in the partitioning, mobilisation, and bio-availability and bio-accumulation of metal and hydrocarbon contaminants in accumulated sediments; c) determining the ecological significance of contaminated sediments in watercourses; d) devising a procedure for the impact assessment of the ecological effects of sediments on receiving watercourses. Here we detail the findings of the first stage of this project; an extensive field survey of 19 sediment accumulating and sediment dispersing sites in England and Scotland. Each site comprised study reaches upstream and downstream of the highway discharge. These were surveyed for benthic macroinvertebrates, and where appropriate, sediment was collected for metal (zinc, cadmium, copper and aluminium) and polyaromatic hydrocarbon (fluoranthene and pyrene) analysis. Nine sites accumulated fine sediment in the downstream study reach. Eight sites lacked accumulation of fine sediment. At two further sites, extensive spatial variation in flow prevented simple classification of sedimentation. Substantial negative impacts upon the macroinvertebrate community were observed more frequently in sediment-accumulating sites (5 of 9) than dispersing sites (1 of 8). Elevated downstream sediment loadings of metals and PAHs were detected at 4 accumulating sites. Contamination by metals alone was observed at 2 accumulating sites. Contaminants were not detected at the remaining 3 accumulating sites. Three accumulating sites and three dispersing sites will be subjected to rigorous further study to identify factors associated with negative ecological impacts.

Key words: pah/metal contamination , highway drainage, sediment toxicity, stream ecology

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