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(38-04) Micro-organic contaminants in the freshwater environment -The role of biofilms in their transport into sediments. Allan, Ian*,1,2, House, William1, Carter, Joy3, Parker, Andrew2, Warren, Nicola2, 1 CEH Dorset, Dorchester, UK2 University of Reading, Reading, UK3 University of Derby, Derby, UK ABSTRACT- Previous monitoring of rivers entering the Humber estuary in the North-East of England revealed the presence of several micro-organic contaminants in river sediments. Four compounds (simazine, lindane, nonylphenol and cis and trans permethrin), with a broad range of physico-chemical properties were found to be widely distributed in the most contaminated rivers, i.e. the rivers Aire and Calder. These were selected for more detailed transport studies using replicate fluvarium channels containing river sediment with flowing overlying water. The results from two fluvarium experiments over a period of 6 weeks are reported. The first experiment was effectuated in the dark with no biofilm development, while the second one was under natural light condition allowing growth of a natural biofilm at the surface of the 50-mm bed of sediment. Sediment reworking was also observed in both experiments due to a natural assemblage of oligochaete worms. Results are presented on the distribution of the compounds in the water, surface biofilm (bacteria and algae) and the top 50-mm bed sediment (both particle-bound and dissolved in pore-waters) taken from the river Calder. A mass balance for each of the compounds revealed the importance of the biofilm, the degree of penetration of the compounds into deeper sediment and the role of degradation in the water and sediment. Degradation results are supported by measurements of their key metabolites in different compartment of the system. Possible ecotoxicological effects of the compounds in pore-waters are reviewed. Key words: micro-organic contaminants, river sediments, biofilm, metabolites |
