The source, composition and fate of selected PAHs in the River Derwent, Derbyshire, and in associated biota.

This work was undertaken in order to determine the extent and nature of PAH pollution In a freshwater riverine environment. An extensive survey of sediment, water and aquatic organisms was carried out to investigate sources of PAH, physicochemical relationships occurring in the water and sediment, the extent of bioaccumulation and the potential for bioconcentration through the food chain. Laboratory studies were designed to investigate the likely mode and extent of uptake of PAH by Noemacheilus barbatulus (L.), Glossiphonia complanata (L.) and Lymnaea peregra (MUller), the ability of these species to metabolise PAH compounds and the extent of depuration. All sediment PAH profiles were similar and indicative of an anthropogenic pyrolytic origin. Urban/road runoff was considered to be a major influence on sediment PAH concentrations. point sources consisted of industrial waste sewage and runoff containing used engine oil. , All sites were affected by diffuse PAH pollution. At certain sites and at times of heavy rainfall this is overlain by a greater input of PAH to the sediment from point sources. Positive linear relationships have been demonstrated between total and individual PAH content and organiC matter content in sediments throughout a range of particle sizes. A similar PAH profile was found in each sediment size fraction, thus organisms selectively removing certain sized particles are not being exposed to differing ratios of PAH compounds. The river system seems to be in a state of nearequilibrium with regard to the partitioning of PAH between bedload sediment, suspended sediment, water and interstitial water. Adsorption and desorption processes occur in two phases, the first being almost instantaneous and the second being a slower approach to equilibrium. There is no- evidence of PAH's being bioconcentrated through the food chain. Uptake by tubificid worms occurs by the ingestion of contaminated sediment. Uptake by Cottus goblo (L.), N. barbatulus, L. peregru, G. complanata and Erpobdella octoculata (t.) occurs mainly through water and was shown to be rapid. N. barbatulus, L. peregra and G. complanat~ have the capacity to metabolise PAH compounds to harmful derivatives and it is likely that C. gobio and E. octoculata also have this capability. Depuration of BaP and metabolite compounds was relatively slow. Prolonged exposure to low levels of BaP in the environment may lead to a buildup of DaP and metabolite compounds in these